PAGE 2

Course work

on the topic: METHODS OF ANALYSIS OF BOTTLE MINERAL WATER IN ACCORDANCE WITH INTERNATIONAL STANDARDS

INTRODUCTION 1.classification 3. Identification and examination Transportation and storage Organoleptic evaluation physical and chemical indicators experimental part 4.2 Determination of the mass fraction of dissolved carbon dioxide 4.3 Determination of the mass concentration of basic ions, specific components, nitrates, nitrites, silver CONCLUSIONS Bibliography

INTRODUCTION

Our planet can be called a water or hydroplanet. The general balance of water in the earth's crust consists of the waters of the World Ocean, glaciers, lakes and rivers, the waters of the atmosphere and the lithosphere (underground hydrosphere). All this amounts to about 1.8 billion km³ of water. A significant amount of saline and mineralized waters of various compositions. The deep zones of the earth's crust are characterized by mineral waters, i.e. waters with a mineralization of more than 1 g / l and containing a number of chemical components.

It is mineral waters that my term paper is devoted to. The purpose of my work is to highlight the main issues about mineral waters, about their classification, features of the chemical composition, gas and temperature conditions, as well as about their use and effect on the human body. A separate chapter of my work includes information on the methods of analysis of bottled mineral water.

I chose this topic because it interested me with its relevance, breadth and significance. Mineral water is a kind of natural medicine created by nature itself. The healing effect of mineral water on the human body, its medicinal properties since ancient times. Resorts, sanatoriums, health resorts, factories for bottling mineral waters have been built on the basis of mineral water deposits. Finally, recently, cases of falsification of mineral waters have become more frequent, therefore there are laboratories that can conduct an examination and identify this or that mineral water. All this speaks about the importance, relevance and relevance of the topic of my course work.

1. classification

According to GOST 13273-88, natural mineral drinking medicinal-table and medicinal waters include natural waters that have a therapeutic effect on the human body, due to the main ion-salt and gas composition, an increased content of biologically active components and specific properties (radioactivity, temperature, reaction Wednesday).

Mineral waters are classified according to several criteria.

According to the degree of mineralization and purpose, they are divided into:

mineral drinking (table) with a mineralization of at least 1 g / dm3 3 or at less, but containing biologically active substances in quantities not lower than balneological standards;

drinking medical table with mineralization from 1 to 10 g / dm3 3 or less, containing biologically active substances;

drinking medicinal with mineralization from 10 to 15 g / dm3 3 or with less in the presence of increased amounts of arsenic, boron, iodine and some other components (Table 1.1).

Table 1.1

Mineral water	Biologically active component	Mass concentration of a component, mg / dm 3, not less
Carbonic acid Glandular Arsenic Borna Siliceous Bromine Iodine	Free carbon dioxide (dissolved) Iron Arsenic Orthoboric acid Metasilicic acid Bromine Iodine Organic matter (calculated as carbon)	500,0 10,0 35,0 50,0 25,0

It is customary to depict the chemical composition of mineral waters in the form of a pseudo-fraction: in the numerator - the predominant anions, in the denominator - cations, the concentration of which is more than 20 mg-eq%. Ions fit in decreasing concentrations, expressed in mg-eq%. To the left of the fraction indicate the total mineralization (in g / dm 3), gases (g / dm 3 ) and biologically active trace elements (in g / dm 3 ). The name of water begins with an ion contained in smaller quantities, this makes it possible to name the prevailing ions completely, and less significant ones - briefly.

According to the chemical composition, mineral waters are divided into 52 groups, within which there is a division into types according to mineralization.

The names of the groups are drawn up according to the principle described above, according to the prevailing anions and cations. For example, water of the composition

called bicarbonate-sulphate calcium.

The types of water are named after the most significant sources.

There is also a technological classification of mineral waters, according to which the scheme of water treatment before bottling is determined.

2. Technology of industrial bottling of natural mineral waters

Natural mineral waters are a complex multicomponent system. Almost all known chemical elements are found in them.

Most waters contain cations in various forms - sodium, calcium, magnesium, potassium; anions - chlorides, sulfates, hydrocarbonates, carbonates, etc. The main trace elements are iodine, bromine, fluorine, selenium, boron, arsenic. In mineral waters, gases are in a dissolved state: carbon dioxide, methane, hydrogen sulfide, nitrogen. Of these, only the first has value, the rest are accompanying and get rid of them.

Among the organic substances present in mineral waters, humic substances, bitumens, phenols, and high molecular weight acids are distinguished. All these substances have one or another therapeutic value.

Mineral waters in natural springs are at different depths. For industrial bottling, they are subject to capturing, i.e. extraction. Capturing - a hydraulic structure for water intake - can be in the form of boreholes, shaft wells, adits, depending on the depth of occurrence and the method of lifting water. Water is transported from the well to the plant through a pipeline, by road, and, at a great distance, by railroad tanks.

In any case, a prerequisite for capturing and transportation is the preservation of the chemical composition, organoleptic characteristics, and microbiological purity. Store water before bottling in sealed containers under CO pressure 2 .

Filter through filter sheets or ceramic filters. The latter are used for waters with salinity up to 7-8 g / dm3. 3 .

Disinfection.The degree of bacterial purity of mineral waters is determined by the presence of Escherichia coli. In bottled mineral waters, their number should be no more than 3 in 1 dm3. 3 (coli-index). During disinfection, all microorganisms, including pathogenic ones, must be destroyed. Use treatment with ultraviolet rays, silver salts, sodium hypochlorite. Waters coming from capturing with a coli-titer of less than 2, as a rule, are not subjected to disinfection.

Cooling carried out to increase the degree of saturation of water with carbon dioxide. Cooled to a temperature not lower than 4-10 ° C in order to avoid disturbing the stability of the salt system of water.

Saturation with carbon dioxideis carried out to preserve water-soluble salts, increase shelf life, and impart flavoring properties. They saturate all mineral waters with CO2; for this, various types of saturators are used. The mass fraction of carbon dioxide in medicinal mineral waters is 0.15-0.20%, in medical-table waters - not less than 0.3%, in ferruginous waters - up to 0.4%.

Poured mineral waters on automated bottling lines, similar to those for bottling beer, soft drinks.

Mineral waters can contain labile components that change under the influence of external factors. Depending on the nature of these components, mineral waters are classified into five technological groups, for each of which special types of treatment are used, in addition to those considered.

I group - non-carbonic (CO-free 2 ) water that does not contain easily oxidized components. The treatment scheme is conventional, including saturation with carbon dioxide.

II group - carbon dioxide (containing CO 2 ). If there are no easily oxidizable components in them, the treatment is carried out according to the usual scheme, but under conditions that ensure a minimum loss of carbon dioxide dissolved in water.

III group - water containing iron. To avoid oxidation of iron, which has medicinal properties, solutions of ascorbic or citric acid are added to the water.

IY group - hydrosulfide and hydrosulfide-hydrogen sulfide containing hydrogen sulfide up to 20 mg / dm3 3 and hydrosulfide ions up to 30 mg / dm 3 ... These reduced forms of sulfur are prone to oxidation to form colloidal sulfur, which gives the water a persistent opalescence. Since these compounds have no beneficial properties, they are removed by flushing with carbon dioxide.

Y group - waters containing sulfate-reducing bacteria, which convert sulfate ions into colloidal sulfur. The vital functions of these bacteria suppressthe introduction of active chlorine. Such water is rarely bottled.

3. Identification and examination

1. Acceptance and sampling rules

Mineral waters are accepted in batches in accordance with GOST 23268.0-91. A batch is considered to be the amount of one type of mineral water bottled in onetype and size or rail tank cars, of the same date of issue and executed in one quality document.

The quality document must contain:

name of the manufacturer and its subordination or namemanufacturer, its subordination and trademark;

name of mineral water;

test results or confirmation of quality compliance NS products to the requirements of regulatory and technical documentation;

for mineral water poured into railway tanks:

number of the railway car (tank);

railway bill number;

volume of transported water;

date of filling;

for bottled mineral water:

nominal water volume;

type of crown cap gasket;

date of issue;

brigade number or rejection number;

batch size.

In each batch, bacteriological and organoleptic indicators, mass concentration of one or two main ions, carbon dioxide, nitrites, nitrates and permanganate oxidizability are determined. In a batch of bottled mineral water, the volume of water and the appearance of the bottles are also determined. In non-carbonic waters transported in railway tanks, the mass concentration of carbon dioxide is not determined.

To control the quality of mineral water, samples for analysis are taken from each tank with a volume of at least 4 dm3. 3 (of which at least 2 dm 3 to control the sanitary and bacteriological state).

To control the quality of bottled mineral water, a sample of product units is selected from each batch by the “blind” selection method for maximum objectivity in accordance with GOST 18321. The sample size is set depending on the volume of the controlled batch. The full sample size is controlled for compliance with the requirements of regulatory and technical documentation for the appearance and external design of bottles.

A batch of mineral water is accepted (Table 3.1) if the number of water bottles with deformation, tears, distortions of labels, salt sediment in the sample is less than or equal to the acceptance number, otherwise they are rejected.

Table 3.1

About m of water batch, bottle.	Sample size, bottle	Acceptance number
151-500 501-1200 1201-10000 10001-35000 35001-150000

To control the compliance of the volume of water, the mass fraction of carbon dioxide, chemical and bacteriological indicators of the finished product with the requirements of GOST 13273 and other regulatory and technical documentation, the number of bottles is selected from the sample according to the requirements given in table. 3.2.

Table 3.2

Sample size, bottle	The volume of water in the bottle.	Mass fraction of carbon dioxide	Chemical indicators	Biological indicators

From a sample of 14 bottles, the control of chemical parameters is carried out after determining the volume of water in the bottles. To conduct an organoleptic assessment, the selection of product units in the sample is carried out according to table. 3.3.

Table 3.3

Lot size, bottle	Sample size, bottle
151-1200 1201-10000 10001-35000 35001-150000

A brief chemical analysis of mineral water, including the determination of the main ions and mineralization, is determined at a frequency of at least once a quarter for waters of deep formation (more than 100 m) and monthly for waters of shallow circulation (up to 100 m) in the sample size according to table. 3.2.

A complete chemical analysis of mineral water, including the determination of components in accordance with GOST 13273 and other regulatory and technical documentation, is carried out at a frequency of at least 1 time per year. In this case, the sample is increased by 10 bottles..

A brief and complete chemical analysis is performed at the institutes of balneology and physiotherapy, at hydrogeological stations of trade union resorts or at specialized hydrochemical laboratories of other organizations.

The sampling of mineral water from the tank is carried out from the nozzle for draining and pouring water or from the tap for sampling. Sampling for sanitary-bacteriological analysis is carried out in accordance with the requirements of GOST 18963 and sanitary rules approved in the prescribed manner.

Control of chemical indicators is carried out from an average sample. Prepare the averaged sample in a clean flask with a capacity of 2000 ml. 3 , pouring mineral water into it from at least four bottles.

1. ... Transportation and storage

Bottles with mineral water are transported by all types of transport in accordance with the rules for the carriage of perishable goods for the respective modes of transport and in universal containers in accordance with GOST 18477.

Bottles with mineral water in container-equipment are transported by all types of transport, except for rail.

Bottles with mineral water, sealed with crown caps with solid-cut cork gaskets, are stored horizontally in boxes or stacks without boxes no more than 18 rows high, and sealed with crown caps with plastisol gaskets - both horizontally and vertically.

Bottles sealed with solid-cut cork crown caps may be stored at the manufacturer in an upright position for a period not exceeding 5 days.

Store mineral water in bottles in ventilated dark rooms at temperatures from 5 to 20 ° C.

During storage, the appearance of individual rust spots on the outer surface of crown corks, which do not violate the tightness of the seal, is allowed.

The manufacturer guarantees the compliance of the bottled mineral waters with the requirements of the standard, subject to the storage and transportation conditions, within 4 months for ferrous waters, 12 months for other waters from the day they are bottled.

3.3. Organoleptic evaluation

Organoleptic characteristics are determined in accordance with GOST 23268.1-91. Transparency, color, taste, smell, saturation with carbon dioxide are evaluated.

In terms of organoleptic characteristics, mineral waters must meet the requirements presented in table. 3.4.

Table 3.4

Index	Characteristic
Appearance Colour Taste and smell	Transparent liquid, without foreign inclusions, with a slight natural sediment of mineral salts Colorless or yellowish to greenish liquid Typical for a complex of substances dissolved in water

Transparency and color are determined visually in transmitted daylight or under fluorescent lighting in a clean glass. Before analysis, the beaker is rinsed with test water.

Before determining the smell, bottled water is kept in a water tank at a temperature of 20-30 ° C for an hour. The tasting glass is then immediately filled and the smell analyzed. To determine the taste, mineral water in a bottle is immersed in a tank with water and ice and kept for one hour at a temperature of 12 ± 1 ° C. The analysis of organoleptic indicators is carried out immediately after filling a glass or glass with water.

The tasting assessment of mineral waters is carried out similarly to non-alcoholic drinks. The total score is given in table. 3.5.

Table 3.5

Index	Minimum point mark
		"Fine"	"Good"	"Satisfied."	"Unsatisfactory"
Transparency Taste Carbon dioxide saturation Points total Boundaries of total scores	25-23	22-20	19-16

Mineral water rated below 16 points is excluded from the tasting.

1. physical and chemical indicators

In terms of physical and chemical indicators, mineral waters must meet the requirements of GOST 13273-88, according to which mineral waters are divided into groups with certain characteristics (salinity (g / dm 3 ), basic ions, (mEq%), the presence of specific components, according to which they have their purpose and certain indications for therapeutic use).

Indications for therapeutic (internal) use of mineral waters:

1. Chronic gastritis.

With normal gastric secretory function.

With increased secretory function of the stomach

With reduced gastric secretory function.

Uncomplicated gastric ulcer and duodenal ulcer. Diseases of the operated stomach for gastric ulcer and duodenal ulcer.

Chronic colitis and enterocolitis.

Chronic diseases of the liver and biliary tract: hepatitis, cholecystitis, angiocholitis of various etiologies without a tendency to frequent exacerbations, calculous cholecystitis, with the exception of
forms complicated by infections and frequent exacerbations, as well as requiring surgery. Postcholecystectomy syndrome.

Chronic pancreatitis.

Metabolic diseases: diabetes mellitus, obesity, gout, uric acid diathesis, oxaluria, phosphaturia.

Chronic diseases of the urinary tract.

Iron deficiency anemia.

When processing mineral water with sulfatesilver or sodium hypochlorite solution, the mass concentration of silver in bottled water should not exceed 0.2 mg / dm3 3 , residual active chlorine - 0.3 mg / dm 3 ... The mass concentration of the following components should not exceed the values ​​given in table. 3.7.

Permanganate oxidizability of mineral waters should be in the range of 0.5-5.0 mg / dm 3 consumed oxygen, and in waters enriched with organic matter, it can be more than 10 mg / dm 3 .

The discrepancy between the oxidizability values ​​in the sources and in the finished product should not exceed 15%.

Table 3.7

Name component	The value of the mass concentration of the component, mg / dm 3, no more	Test Method
Nitrates (by) Nitrite (by) Lead Selenium Uranus Arsenic per metal: In medicinal waters In medicinal table waters Strontium Fluorine: In medicinal waters In medicinal table waters Phenols in medicinal waters and medicinal table waters Other organic matter (calculated as carbon): In medicinal waters In medicinal table waters For th	50,0 0,05 1.8 (1.2 × 10 -9 Ci / dm 3) 25,0 15,0 10,0 0,001 15,0 10,0 5 × 10 -10 Ci / dm 3	According to GOST 23268.9 According to GOST 23268.8 According to GOST 18293 According to GOST 19413 According to NTD According to GOST 23268.14 According to GOST 23950 According to GOST 23268.18 According to the methodology approved by the Ministry of Health of the Russian Federation also

1. Microbiological and other safety indicators

According to bacteriological indicators, mineral waters must meet the requirements of Table. 3.8.

Sanitary and bacteriological control of mineral waters is carried out in accordance with GOST 18963. The terms of inspection are determined by sanitary rules, approved in the prescribed manner.

Table 3.8

Index	Value, no more	Test Method
The total number of bacteria in 1 cm 3 mineral water The number of bacteria of the Escherichia coli group in 1 dm 3 mineral water		According to GOST 18963 According to GOST 18963

4.Experimental part

For the course work, we took three types of mineral bottled water "Borjomi", "Nabeglavi "and" Essentuki No. 4 "with a capacity of 0.5 liters. Each bottle is labeled with labels indicating the name of the medicinal mineral water, as well as its main characteristics, which are shown in Table 4.1.

Table 4.1

Main characteristics	Manufacturer	Medical indicators for use	Chemical composition (mg / dm 3 )
Borjomi
Mineral water, medicinal-table sodium bicarbonate. Highly carbonated.	The company ”IDS BORJOMIBEVERAGES Co. N. V . ”1200, Georgia, Borjomi, st. Tori, 39. Addresses of production facilities: AT "Georgian Mineral Waters - Borzhomi Bottling Plant No. 2". 1209, Georgia, Borjomi district Spilled at the site of extraction from the Borjomi mineral water deposit from St. No. 25 with a depth of 1500m. manufactured according to STG 50, post in according to TU U 15.9-24364528-001	Chronic gastritis with normal and increased gastric secretory function; uncomplicated gastric ulcer and duodenal ulcer; chronic colitis and enterocolitis; chronic diseases of the liver and biliary tract; chronic pancreatitis; metabolic diseases, are used as a therapeutic one with the recommendation of a doctor and as table drinks in case of unsystematic use for more than 30 days with an interval of 3-6 months. Store in a special ventilated warehouse, protected from moisture, at a temperature of +3 0 C to +30 0 C, keep away from direct sunlight.	HCO 3 - SO 4 2- Cl - Ca 2+ Mg 2+ Na +	3500-5000 250-500 20-150 20-150 1000-2000 15-45
						Contains fluoride; Artificially saturated with CO 2 ; Mineralization: 5.0-7.5 g / dm 3 .
Raid
Mineral natural medicinal table water.	AT "Health Water". Georgia, Chokyazhursky district, s. Nabeglavi, 4915. Produced from wells 2zh, 17, 44, 47, 66a	Chronic gastritis with normal and increased gastric secretory function; uncomplicated peptic ulcer of the stomach and duodenum; chronic colitis and enterocolitis; chronic diseases of the liver and biliary tract; chronic pancreatitis, metabolic diseases; diabetes; disorders of fat metabolism. It is used as a therapeutic one upon the recommendation of a doctor and as table drinks in case of unsystematic use for more than 30 days with an interval of 3-6 months. Store in a special ventilated warehouse, protected from moisture, at a temperature of +5 0 C to +20 0 C	Bicarbonates Sulphates Chlorides Calcium Magnesium Sodium + potassium		2400-4400 70-244 42-95 36-112 34-120 930-1270
						Bicarbonate sodium silicon boric acid, highly carbonated, artificially saturated with CO 2 . Metasilicic acid 55-90 mg / dm3 3 ; Orthoboric acid> 35 mg / dm 3 ; Mineralization of water 3.5-5.9 g / dm 3.
Essentuki No. 4
Mineral drinking natural medicinal-table water.	LLC "Universal plant for bottling mineral water" AQUA-VFYT ". Russia, 357600, Stavropol Territory, Essentuki, st. Novopyatigorskaya, 1.	Chronic gastritis with normal and increased gastric secretory function; uncomplicated gastric ulcer and duodenal ulcer; diseases of the operated stomach and duodenum; chronic colitis and enterocolitis, chronic liver disease; urinary and biliary tract; hepatitis, cholecystitis; chronic pancreatitis; metabolic diseases: diabetes mellitus, obesity, gout, uric acid diathesis, oxaluria, phosphaturia. Postcholecystectomy syndrome. In the case of the above diseases, water is used only outside the exacerbation phase. Natural precipitation of mineral salts is permitted. Store in rooms protected from moisture, at temperatures from +5 0 C to +20 0 C.	HCO 3 - SO 4 2- Cl - Ca 2+ Mg 2+ Na +, K +	3900-4900 1100-1900 <150 <100 2000-3000
						HBO… .35-150; CO ... 500-2000; Mineralization: 7.0-10.0 g / dm 3 .

1. Determination of the volume of bottled water

The volume of water in bottles is determined in accordance with GOST 23268.1-91 by measuring using measuring cylinders at a temperature of 20 ± 1 ° C. Mineral water, sealed in bottles, is placed in a tank with water and kept for 1 hour. The contents of the bottles are carefully poured along the wall into dry cylinders, while from bottles with a capacity of 0.33; 0.5 and 1.0 dm 3 , respectively, in cylinders with a capacity of 250, 500 and 1000 ml 3 , and excess water in a cylinder with a capacity of 100 ml 3 ... The volume of mineral water is determined by the lower meniscus with an error not exceeding the graduation rate of the cylinder.

The arithmetic mean of the filling of ten bottles in cubic centimeters is taken as the final result of determining the volume of mineral water in bottles. Calculate the deviation value as a percentage of the nominal volume of water in the bottle.

1. Determination of the mass fraction of dissolved carbon dioxide

The mass fraction of dissolved carbon dioxide is determined according to GOST 23268.2-91 by the manometric or titrimetric method.

In this course work, I carry out a titrimetric method based on the absorption of carbon dioxide by alkali with the formation of carbonate ions, which pass into bicarbonate ions upon acidification. The amount of dissolved carbon dioxide is determined by the difference between the total mass concentration of bicarbonate ions and their mass concentration in the source water. The method makes it possible to determine from 5 mg of bicarbonate ions in a sample.

Prepared sample (quickly uncork the bottle and pour 20-40 cm 3 mineral water to alkaline charge - 10 cm 3 1 M solution of sodium hydroxide) quantitatively transfer to a flask for titration, add 2 drops of phenolphthalein solution and titrate with 0.1 M solution of hydrochloric acid until the solution becomes discolored. The volume of acid consumed for titration for phenolphthalein is not taken into account.

Determination of the initial mass concentration of bicarbonate ions.

The mass concentration of bicarbonate ions is determined in accordance with GOST 23268.3.

3 take from 25 to 50 cm 3 analyzed water, the volume of the sample is brought up to 100 ml with distilled water 3 , add 2-3 drops of methyl orange solution and titrate with 0.1 M hydrochloric acid solution until the color of the solution changes from yellow to pink. If there are more than 300 mg / L bicarbonate ions in the test water, after the end of titration, the water sample is boiled under a reflux condenser for 5-7 minutes (the reflux condenser was replaced with an inverted funnel). If the color of the solution changes to yellow, the sample is titrated with hydrochloric acid.

Mass concentration of bicarbonate ions (X), g / dm 3 , calculated by the formula

Where V n - volume of hydrochloric acid solution consumed for titration, cm 3 ;

n - normality of hydrochloric acid solution;

61 - gram equivalent of bicarbonate ions;

V - the volume of water taken for analysis, cm 3 ;

The total mass concentration of bicarbonate ions (X 1) g / dm 3 , calculated by the formula: X 1 = V 1 × M × 61 / V 2 - V 3,

where V 1 - the volume of hydrochloric acid solution consumed for titration by methyl orange, cm 3 ;

M - molarity of hydrochloric acid solution;

61 - molar mass equivalent of the hydrocarbonate ion;

V 2 - total volume of sample and alkaline charging, cm 3 ;

V 3 - volume of alkaline charging, cm 3 .

The mass concentration of dissolved carbon dioxide (X 2), g / dm 3 , calculated by the formula:

X 2 = (X 1 - X) × 0.72,

where X 1 - total mass concentration of bicarbonate ions, g / dm 3 ;

X - initial mass concentration of bicarbonate ions, g / dm 3 ;

0.72 - conversion factor of the amount of bicarbonate ions, per equivalent amount of carbon dioxide g / dm3 3 .

Calculations are carried out up to 0.001 g / dm 3 with subsequent rounding of the result to 0.01 g / dm3 3 .

The research results are shown in table 4.2.

Table 4.2

Name of water		V n					X 1	X 2
Borjomi		2,35	33,75			4,75	6,86	1,52
"Raise"		0,75	17,15			1,50	3,48	1,43
"Essentuki No. 4"		0,85	13,45			1,71	2,73	1,02

As a result of the study, it was found that all the investigated mineral waters contain dissolved carbon dioxide, the indicators of which correspond to those indicated on the label.

1. Determination of the mass concentration of basic ions, specific components, nitrates, nitrites, silver

Mass concentration of basic ions, specific components, nitrates, nitrites,silver is determined according to GOST 23268.3-23268.9, GOST 23268.11, GOST 23268.13-23268.18.

In this work, only some of the methods for the determination of nitrates and nitrites will be presented.

To determine nitrite ions, colorimetric methods are used: visual and photometric, based on the formation of a red azo dye during the reaction of nitrite ions with the Griss reagent.

When examining mineral water by the visual method, 1 cm is added to the test tube. 3 analyzed water. Simultaneously prepare a standard solution with a content of 2 mg / dm 3 nitrite ions, for which 1 dm3 is added to the same test tube 3 working standard solution. 5 cm are added to the contents of the tubes 3 Griss reagent solution. The volumes of solutions are adjusted with distilled water to 20 cm 3 ... After 20 minutes, the color intensity of the analyzed solution is compared with the color intensity of the reference solution in transmitted light. The products comply with the requirements of the current regulatory and technical documentation, if the color intensity of the analyzed solution does not exceed the color intensity of the standard solution in two parallel determinations.

The presence of nitrate ions in mineral water is established by colorimetric and potentiometric methods.

The colorimetric method of determination with diphenylamine is intended for the rapid determination of the maximum permissible content of nitrate ions in mineral waters. The method is based on the oxidation of diphenylamine with nitrate ions to form a blue-colored quinoid diphenylamine derivative. The method allows the determination of nitrate ions from 0.001 to 0.005 mg in a sample.

Add 1 cm to a dry test tube 3 prepared sample. Simultaneously prepare standard solutions with a nitrate ion content of 0.0; 1.0; 2.0; 5.0 mg / dm 3 , for which, respectively, 1 cm is introduced into the same test tubes 3 prepared working standard solutions of potassium nitrate (solutions No. 2, 3, 4).

Add 0.1 cm to the contents of the tubes from the microburette 3 10% solution of sodium chloride, carefully pour in 2.5 cm 3 diphenylamine reagent, stirred with a glass rod and placed in a glass of water at a temperature from 18 to 22 O C. After 2.5 hours compare the color intensity of the test solution with the color intensity of the standard solutions.

Preparation of diphenylamine reagent: involumetric flask with a capacity of 100 ml 3 add 38 cm 3 distilled water, add 5 ml 3 the basic solution of diphenylamine, the volume of the solution is carefully brought to the mark with concentrated sulfuric acid, stirred and left to stand for 3 to 5 days. The reagent should be colorless.

Preparation of the basic solution of diphenylamine: 0.1 g of diphenylamine is weighed with an error of not more than ± 0.0002 g, placed in a volumetric flask with a capacity of 100 ml 3 , carefully dissolve in sulfuric acid and bring the volume of the solution to the mark with the same acid.

Mass concentration of nitrate ions (X), mg / dm 3 , calculated by the formula X = C × V 2 / V 1, where

C - mass concentration of nitrate ions, mg / dm 3 ;

V 2 - the volume to which the sample is diluted, cm 3 ;

V 1 - volume of analyzed water taken for dilution, cm 3 .

In case of disagreements in assessing the quality of mineral drinking medicinal, medical table and natural table water, the colorimetric method of determination with phenol disulfonic acid is used.

4.4. Determination of the concentration of residual active chlorine

Free (residual) chlorine. It is hypochlorous acid, its dissolution products and chlorine molecules.

The mass concentration of residual active chlorine is determined according to GOST 18190 by three methods.

In carrying out this course work, a study will be carried out only by the iodometric method and titration with methyl orange.

Iodometric method.

Pour 0.5 g of potassium iodide into a conical flask, dissolve it in 1 - 2 cm 3 distilled water, then add a buffer solution in an amount approximately equal to one and a half the alkalinity of the analyzed water, after which add 250 - 500 ml 3 analyzed water. The released iodine is titrated with a 0.005 M sodium thiosulfate solution from a microburette until a light yellow color appears, after which 1 ml of a 0.5% starch solution is added and the solution is titrated until the blue color disappears.

where v - the amount of 0.005 M sodium thiosulfate solution consumed for titration, cm 3 ;

K - the correction factor for the normality of the sodium thiosulfate solution is calculated by the formula K = 10 / v (v - amount of sodium sulfate consumed for titration, ml);

0.177 - the content of active chlorine, corresponding to 1 cm 3 0.005 N sodium thiosulfate solution;

V - volume of water sample taken for analysis, cm 3 .

The methyl orange titration method is based on the oxidation of methyl orange with free chlorine, in contrast to chloramines, the oxidative potential of which is insufficient to destroy methyl orange.

Place 100 ml of the analyzed water in a porcelain cup, add 2-3 drops 5 M solution of hydrochloric acid and, stirring, rapidly titrate with a solution of methyl orange until a non-disappearing pink color appears.

X 1 = (0.04 + (υ 1 ∙ 0.0217) ∙ 1000) / V 1,

where υ 1 - the amount of 0.005% methyl orange solution consumed for titration, ml;

0.0217 - titer of methyl orange solution;

0.04 - empirical coefficient;

V 1 - volume of water taken for analysis, ml;

By the difference between the content of the total residual chlorine, determined by the iodometric method, and the content of free residual chlorine, determined by the titration method, methyl orange, the content of chloraminic chlorine (X 2 ):

X 2 = X - X 1.

The research results are shown in Table 4.3.

Table 4.3

Name of water	V, ml	υ, ml	V 1, ml	υ 1, ml	X, mg / l	X 1, mg / l	X 2, mg / l
Borjomi		36,50		35,00	0,26	0,01	0,25
"Raise"		16,06		48,50	0,12	0,02	0,10
"Essentuki No. 4"		17,54		118,00	1,23	0,03	1,20

4.5. Determination of the concentration of permanganate oxidizability

Permanganate oxidizability of water is a value that characterizes the content of organic and mineral substances in water, oxidized (under certain conditions) by one of the strong chemical oxidants, in our case, with the help of potassium permanganate (potassium permanganate). This indicator reflects the total concentration of organic matter in the water.

The mass concentration of permanganate oxidizability is determined in accordance with GOST 23268.12.

The method is based on the oxidation of organic substances with a solution of potassium permanganate in acidic or alkaline media during boiling. The method allows you to determine the amount of organic matter, the oxidation of which is consumed up to 10 mg / dm 3 oxygen.

The presence of sulfide ions, nitrite ions, and iron ions ( II).

1 mg H 2 S - correspond to 0.047 mg of consumed oxygen;

1 mg NO 2 - corresponds to 0.35 mg of consumed oxygen;

1 mg Fe (II ) - corresponds to 0.14 mg of consumed oxygen.

Determination of oxidizability in an acidic medium (at a mass concentration of chloride ions in water less than 300 mg / dm 3 ).

Into a 250 ml conical flask 3 make 100 cm 3 3 consumed oxygen for analysis, take a smaller volume of water), place several pieces of porous porcelain, add 5 cm 3 sulfuric acid (1: 2) and 20 cm 3 0.01 M solution of potassium permanganate. Cover the flask with a watch glass and boil from the moment of boiling for 10 minutes.

Pour 20 cm into the hot solution 3 0.01 M solution of oxalic acid and immediately titrate 0.01 M solution of potassium permanganate to pink color. A blank experiment is carried out in parallel. To do this, take 100 cm 3 distilled water and treat it in the same way as the analyzed water.

Determination of oxidizability in an alkaline medium (at a mass concentration of chloride ions in water of more than 300 mg / dm 3 ).

Into a 250 ml conical flask 3 contribute 100 cm 3 analyzed water (with an oxidizability value of more than 10 mg / dm 3 consumed oxygen for analysis, take a smaller volume of water), place several pieces of porous porcelain, pour 0.5 cm 3 concentrated sodium hydroxide solution and 20 ml 3 0.01 M solution of potassium permanganate. Cover the flask with a watch glass and boil from the moment of boiling for 10 minutes. Add 5 ml of sulfuric acid (1: 2), 20 cm 3 0.01 M solution of oxalic acid and immediately titrate with 0.01 N solution of potassium permanganate to pink color. A blank experiment is carried out in parallel.

Oxidability (X), mg / dm 3 , consumed oxygen is calculated by the formula: X = (V - V 1) × n × 8 × 1000 / V 2, where

V - volume of potassium permanganate solution consumed for titration of the analyzed water, ml;

V 1 - volume of potassium permanganate solution consumed for titration of a blank sample, ml;

n - molar concentration of the equivalent of a solution of potassium permanganate;

8 - molar mass of oxygen equivalent;

V 2 - volume of water sample taken for analysis, ml.

The arithmetic mean of three parallel determinations is taken as the final result, the allowable discrepancies between which should not exceed 2%.

The results obtained during the study are entered in table 4.4.

Table 4.4

Name of water	n, mol / L equiv.	V, ml	V 1, ml	V 2, ml	X, mg / l
Borjomi	0,01	3,00			2,16
"Raise"	0,01	4,20		100	3,0
"Essentuki No. 4"	0,01	5,80	0,5	100	4,0

Increase in permanganate oxidizability more than 4.0 mg O2 per 1 liter indicates a possible pollution of the water source with substances of organic and mineral origin. Minimum oxidizability (up to 2.0 mg O2 per 1 liter) is usually characterized by artesian waters.

In this work, it was found that the permanganate oxidizability of the studied mineral waters is normal and does not exceed the maximum permanganate oxidizability of 4 mgO2 / l in Ukraine, and in Russia this indicator is 5 mgO2 / l.

CONCLUSIONS

So, in conclusion, we can conclude: mineral (medicinal) waters include natural waters, which can have a therapeutic effect on the human body, due either to an increased content of useful, biologically active components of the ion-salt or gas composition, or to the general ion-salt composition of water ... Mineral waters are not any specific genetic type of groundwater. These include waters that are very different in terms of formation conditions and differ in chemical composition. For medicinal purposes, waters with mineralization from fractions of a gram per 1 liter to highly concentrated brines, various ionic, gas and microcomponent compositions, and various temperatures are used. Among the underground waters related to mineral, infiltration and sedimentation, as well as waters, in one way or another, associated with modern magmatic activity, are distinguished. They are widespread in various hydrodynamic and hydrothermal zones of the earth's crust, in a diverse geochemical setting, and can be confined to aquifers spread over vast areas or can be strictly localized fissure-vein waters.

To resolve the issue of identifying bottled mineral water and assigning it to a specific group, certain methods of analysis are used, which are carried out in accordance with the requirements of international standards.Upon receipt of unsatisfactory test results for at least one of the indicators for which the acceptance and rejection numbers are established, the batch is rejected.

The research data are very important because Mineral drinking and medicinal-table waters should have medicinal properties and in no case should harm a person.

Bibliography

1. Oreshko A.V., Beresten N.F. Soft drinks // Food industry, No. 5,2009 , p. 26.
2. Rudolf V.V., Yashkova P.M., Oreshko A.V. Craftsman's Handbooksproduction of soft drinks. - M .: Agropromizdat,200 8.191s.
3. Expertise of drinks / V.M. Poznyakovsky, V.A. Pomozova, T.F. Kiseleva, L.V. Permyakova, 4th bridle, rev. and add. - Novosibirsk: Sib.univ.izd-vo; Novosibirsk University Publishing House, 201 1.384s.

UDC: 613.31: 543.3 (048.8) CHEMICAL COMPOSITION OF MINERAL WATERS OF THE BELGOROD REGION

The study of the chemical composition of 12 types of packaged mineral waters produced in the Belgorod region was carried out. The active concentration of water (pH), its total hardness were determined, the content of calcium, magnesium, bicarbonate, sulfate, chloride, fluoride, iodide ions and total iron (II and III) was determined. The comparison of the indicated indicators of water quality with those for water from centralized drinking water supply systems is carried out. A biochemical assessment of the results obtained is given.

Key words: mineral water, cation-anionic composition, quality standards, physiological usefulness of drinking water.

L.F. Goldovskaya-Peristaya, I.V. Indina, VA Peristyi, M.N. Yapryntsev

Belgorod State National Research University, Russia, 308015, Belgorod, st. Victory, 85

Email: [email protected]

Introduction

Mineral waters include underground (sometimes surface) natural waters, which are characterized by an increased content of biologically active components and have specific physicochemical properties (temperature, chemical composition, radioactivity, etc.).

Mineral waters are used for medicinal and industrial purposes. Medicinal waters include those waters that, due to their physical and chemical characteristics, have a healing effect on the human body (carbon dioxide, hydrogen sulfide, etc.). The industrially valuable waters are those from which components useful in the national economy (table salt, bromine, iodine, boron) can be extracted.

To classify natural waters as mineral waters, special criteria have been developed that characterize the physiological, and, therefore, therapeutic, effect of waters. These criteria include:

Active reaction of waters, characterized by the pH value;

Water temperature;

Ionic composition of mineral waters;

Gas saturation of waters;

Water radioactivity.

Depending on the quality of the water, improved in relation to the hygienic requirements for the water of the centralized water supply, as well as additional medical and biological requirements, the bottled water is divided into 2 categories.

The first category is drinking water (regardless of the source of its production), safe for health, fully complying with the criteria of favorable organoleptic properties, epidemic and radiation safety, chemical composition harmlessness and stably retaining its high drinking properties.

The highest category is water that is safe for health and optimal in quality (from independent, as a rule, underground, preferably spring or artesian water sources, reliably protected from biological and chemical pollution).

While maintaining all the criteria for water of the 1st category, drinking water of optimal quality must also comply with the criterion of physiological usefulness in terms of the content of the main biologically necessary macro- and microelements and more stringent standards for a number of organoleptic and sanitary-toxicological indicators.

The chemical composition of mineral waters is determined by the content of three anions - HCO3-, 5042_, C1- and three cations - Ca2 +, Mg2 +, Na +. The ratio of these six elements determines the basic properties of groundwater - alkalinity, salinity and hardness. According to the anionic composition, mineral waters are classified into:

Chloride (C1-);

Sulfate (5042-);

Hydrocarbonate (НСО3-);

Intermediate (hydrocarbonate-sulfate, sulfate-chloride, chloride-sulfate and more complex composition).

According to the cationic composition, mineral waters can be:

Sodium (Noa +);

Calcium (Ca2 +);

Magnesium (Md2 +);

Mixed.

The chemical composition of groundwater, including mineral water, is formed under the influence of many natural factors and has its own regional characteristics in different geographic zones. It is rarely balanced in a ratio favorable to the human body and is usually characterized by an excess or insufficient content of certain macro- or microelements.

On the territory of the Belgorod region, mineral underground waters were discovered along the way during the exploration of deposits of solid minerals. The following groups of mineral waters are distinguished: balneological, mineral medicinal, mineral drinking medicinal-table and mineral table. The first group (balneological waters) includes radon waters, which are used in the form of radon baths. Deposits of mineral medicinal waters are widespread in Belgorodsky, Starooskolsky, Shebekinsky, Chernyansky districts. Mineral drinking medical dining rooms are widespread in Belgorodsky, Shebekinsky, Borisovsky and Rakityansky districts. Mineral table waters are found in the Belgorodsky, Yakovlevsky, Prokhorovsky and Shebekinsky districts. They are called ecologically clean groundwater because they are reasonably well protected from pollution. Such underground mineral waters can be used for bottling without special reagent water treatment both in natural form and with saturation with carbon dioxide (carbonated water), as well as for the preparation of soft drinks, juices, baby food, etc.

The purpose of this work was to assess the quality of mineral drinking medicinal table and table waters of the Belgorod region by the active reaction (pH) and ionic composition.

Research methods

For the study, 12 types of packaged mineral waters produced in the Belgorod region were taken: Aqua Futuri, Blagodatny source, Krasivo, Epiphany Spring, Maiskaya Khrustalnaya, Path to the top, Spring Belogorya, Rozhdestvenskaya, Saninskaya, Standard Belogorya, Crystal Belogorya, Yasny well.

The total hardness, the content of calcium, magnesium, bicarbonate, sulfate and chloride ions were determined by the titrimetric method according to the relevant State Standards. The active reaction of the waters, characterized by the pH value, was determined by the potentiometric method. The concentration of trace elements (iodide and fluoride ions) was determined according to standard methods. To determine the concentration of iodide ions, we used a photometric method based on the catalytic action of the iodide ion on the oxidation reaction of the iron (III) thiocyanate ion. The concentration of fluoride ions in water was determined by the ionometric method using a B-selective electrode. The concentration of total iron (II and III) was determined by the spectrophotometric method according to the corresponding GOST.

Results and its discussion

Table 1 shows the general characteristics of the investigated mineral waters. The water class is declared by the manufacturer, and the pH value was determined by us experimentally.

Mineral waters of the Belgorod region are extracted from artesian wells at a depth of 320 to 737 m.

Table 1

General characteristics of the investigated mineral waters

No. Name of water Artesian well depth, m Water class by anionic-cationic composition pH Mineral water producer

1 Aqua-Futuri 320 of the first category 7-34, Valuyki, JSC Valuy Distillery

2 Blagodatny source 737 dining room, sodium bicarbonate 8.67 Belgorod district, p. Veselaya Lopan, "Vese-Lolopansky distillery"

3 Beautifully 679 dining room, sodium bicarbonate, medical 8.66 Borisovskiy district, health resort "Krasivo"

4 Epiphany Spring 320 dining room, hydrocarbonate-chloride sodium 7.72, Valuyki, JSC Valuysky distillery

5 Mayskaya Khrustalnaya 640 dining room, sodium bicarbonate 8.45 Belgorod, Mayskiy settlement, OJSC "White Mountains"

6 Path to the top 320 of the highest category 5.21 Valuyki, JSC Valuy Distillery

7 Spring Belogorya 500 dining room, sodium bicarbonate 8.58 Korocha, JSC "Belogorye and K"

8 Christmas 465 dining room, sulphate-hydrocarbonate sodium 8.25 Yakovlevsky district, Stroitel, OOO "Rodnik"

9 Saninskaya 385 dining room, bicarbonate calcium-sodium 8.05 Korochansky district, p. Gremyachye, JSC "Agroproduct"

10 Standard Belogorya - canteen, sulphate-hydrocarbonate sodium 8.29, Belgorod, LLC "Water World"

11 Crystal Belogorya 496 dining room, sodium bicarbonate 8.43 Belgorod, JSC "Elgaz-Plus"

12 Yasny well - canteen, bicarbonate calcium 7.83, Korocha, LLC "Belogorye and K"

Packaged drinking water quality standards First category - 6.58.5 -

Our studies have shown that the pH of the investigated mineral waters is 7.348.67. The pH value of the Path to the Top mineral water is not taken into account, since this water is sold only in carbonated form and cannot be compared with other waters in terms of this indicator. Most of the examined mineral waters meet the hygienic requirements and quality standards for drinking water, packaged in containers, the pH of which should be 6.5-8.5. However, the mineral waters "Blagodatny Spring" and "Krasivo" slightly exceed the specified standard. In terms of acid-base properties, the mineral waters under study are weakly alkaline, for which pH = 7.2-8.5.

Many authors note that it is very important to drink water with an alkaline pH value, since most biological fluids of the human body have an alkaline reaction of the environment: arterial blood pH 7.35-7.45, venous blood - 7.26-7.36, lymph - 7.35-7.40, intercellular fluid - 7.26-7.38, pancreatic juice - 7.50-8.0, bile in the ducts - 7.4-8.5, etc.

Table 2 shows the results of determining the chemical composition of 12 mineral waters of the Belgorod region. Let's compare them with the hygienic requirements and standards for the quality of drinking water, packaged in containers.

According to the value of the total hardness, more than half of the studied mineral waters belong to the group of very soft natural waters, the hardness of which is less than the lower value of the standard for the quality of waters of the highest category and the standard for physiological usefulness.

drinking water, i.e. less than 1.5 mmol / l. The hardness of the rest of the waters meets the specified standards (1.5-7 mmol / l).

table 2

Chemical composition of mineral waters of the Belgorod region

No. Name of water L, mmol / l Ca2 +, mg / l Mg2 + mg / l HCO3 -mg / l 8042-, mg / l C1-, mg / l B-, mg / l mg / l Fe (total) , mg / l

1 Aqua-Futuri 1.40 23.6 2.6 51.7 33.93 18.9 0.44 0.010 0.017

2 Blessed spring 0.10 2.0 Not found 328.5 2.79 30.2 1.67 0.031 0.024

3 Beautiful 0.10 2.2 0.8 265.7 38.52 39.5 1.12 0.015 0.066

4 Epiphany Spring 4.33 56.6 18.0 184.5 44.91 279.5 1.83 0.021 0.006

6 Path to the top 1.97 28.4 6.6 62.7 35.53 34.1 1.04 0.009 0.011

7 Spring of Belogo-Rya 0.20 4.0 Not found 175.3 104.39 22.0 0.99 0.025 0.002

8 Christmas 0.37 6.0 0.8 145.8 100.0 0 16.3 0.60 0.025 0.002

9 Saninskaya 1.95 27.5 6.9 132.9 56.89 15.6 0.35 0.016 0.003

10 White-Rya standard 0.50 8.0 1.2 155.0 41.12 37.6 0.69 0.007 0.023

11 Crystal White-Rya 0.40 6.0 1.2 199.3 24.15 27.0 1.56 0.012 0.038

12 Clear well 5.57 102.0 5.6 179.0 32.33 27.0 0.12 0.014 0.018

Packaged drinking water quality standards First category 7 130 65 400 250 250 1.5 0.125 0.3

Standards for the physiological usefulness of drinking water, within 1.5-7 25130 5-65 30400 - - 0.51.5 0.010.125 -

The results of determining the content of calcium and magnesium ions in mineral waters show that more than half of the studied waters are characterized by a low content of calcium and magnesium ions and do not reach the lower physiological value of 25-130 mg / l (for calcium ions) and 5-65 mg / l ( for magnesium ions). Only the mineral waters "Kreshchensky Rodnik", "Path to the Top", "Saninskaya" and "Yasnyi kolodets" meet the standards of the physiological usefulness of drinking water. In terms of the content of these ions, the waters of the Epiphany Spring, Path to the Top and Saninskaya also correspond to the water quality standard of the highest category (25-80 mg / l (for calcium) and 5-50 mg / l (for magnesium)).

As a result of research by a number of authors, the minimum and maximum concentrations of calcium and magnesium ions in drinking water have been established, which cause dysfunction of organs and systems of the human body. For waters of the hydrocarbonate class, the optimal concentrations should be considered: Ca2 + - 60 mg / l, Mg2 + - 26 mg / l. The content of calcium and magnesium in the investigated mineral waters does not correspond to the specified optimal ratio.

Previously, we found that the hygienic standards for water quality of centralized drinking water supply systems (CPWS) in the Belgorod region were exceeded in terms of total hardness and concentration of calcium ions. The total hardness of the CSPV water is 5.8-11.4 mmol / l (in various districts of the region). It was revealed that the water of the CSPV did not comply with the quality requirements for hardness in 20 regional centers out of 21 (95% of the samples). The hardness of Belgorod tap water is mainly due to calcium ions, the concentration of which is 104-174 mg / l. The content of magnesium ions is much less (7-58 mg / l) than ions

calcium. However, in terms of the content of magnesium ions, water in all regional centers meets hygienic requirements.

Comparison of the investigated mineral waters with the water of the CSPV of the Belgorod region shows that the total hardness and the content of calcium ions in mineral waters are much less than in tap water, which, on the one hand, can be considered a favorable factor, since the high hardness of drinking water is one of the reasons urolithiasis and hypertension. However, on the other hand, the constant use of soft water with a low calcium ion content can negatively affect the skeletal system. In contrast to the water of CSPV, more than half of the studied types of mineral waters do not meet the quality standards for packaged drinking water in terms of the content of magnesium ions. The insignificant content of magnesium in drinking mineral waters does not allow them to be considered a complete alternative to tap water, since the constant use of such mineral waters can negatively affect the cardiovascular system.

The content of hydrocarbonate ions in the investigated mineral waters corresponds to the standard of physiological usefulness and the quality standard for waters of the highest category. Higher concentrations of hydrocarbonate ions belong to the waters "Blagodatny source" (328.5 mg / l), "Maiskaya Khrustalnaya" (308.5 mg / l), "Krasivo" (265.7 mg / l). Most of the investigated mineral waters can be classified as hydrocarbonate. Mineral waters "Aqua-Futuri" and "Path to the Top" have low concentrations of hydrocarbonate ions, equal to 51.7 and 62.7 mg / l, respectively.

It is known that mineral waters containing hydrocarbonate ions normalize the secretory and motor functions of the stomach and intestines. Under the influence of hydrocarbonate waters in the body, the content of hydrogen ions, which are the starting material for the production of hydrochloric acid, decreases. The presence of HCO3- ions in the water promotes better absorption of certain trace elements in the intestine, in particular iron.

The content of sulfate ions in the waters under study varies widely from 2.8 to 104.4 mg / L, which does not exceed the values ​​of the considered standards for waters of the first and highest categories. Mineral water "Standard Belogorya" is declared by the manufacturer as sulfate, but the concentration of sulfate ions in it is only 41.12 mg / l. Only two mineral waters contain a significant amount of sulfate ions: "Spring Belogorya" (104.39 mg / l) and "Rozhdestvenskaya" (100 mg / l), which allows them to be classified as sulfate waters.

From the literature it is known that sulfate mineral waters significantly reduce the activity of gastric secretion, have a pronounced effect on the intestines and increase metabolic processes in the body.

Although in terms of the concentration of chloride ions, mineral waters produced in the Belgorod region differ significantly from each other, but almost all of them meet the quality standard for waters of the highest category. In general, the content of chloride ions in them is low and therefore they cannot be classified as chloride ions. An excess of chloride ions is observed only in the Kreshchensky Rodnik mineral water (279.5 mg / l), which significantly exceeds the quality standard for waters of the highest category (150 mg / l) and the quality standard for waters of the first category (250 mg / l). Such chloride mineral water should increase metabolic processes, cause a choleretic effect, and with prolonged use, contribute to an increase in the acidity of gastric juice. And in combination with calcium ions, the content of which in the water "Epiphany Rodnik" is 56.6 mg / l, it can have an anti-inflammatory effect, reduce the permeability of cell membranes, reduce bleeding, have a beneficial effect on the growth of bone tissue and teeth.

In terms of the concentration of fluoride ions (0.12-1.83 mg / l), the investigated mineral waters differ significantly from each other. Almost half of them correspond to the standard of physiological usefulness and the quality standard for waters of the highest category. The lack of fluoride ions was found in the mineral waters "Aqua-Futuri" (0.44 mg / l), "Saninskaya" (0.35 mg / l) and "Yasnyi kolodets" (0.12 mg / l). A significant excess of the MPC for the content of fluoride ions was recorded in the mineral waters "Kreshchensky Rodnik" (1.83 mg / l), "Blagodatny source" (1.67 mg / l), "Maiskaya Khrustalnaya" (1.63 mg / l), which does not allow them to be attributed to waters of the first and highest category for this indicator.

As is known from the literature, osteoporosis and dental caries are among the manifestations of fluoride deficiency, and the consequence of an excess of fluoride is fluorosis, which is externally expressed in spotting of the teeth.

Our earlier studies showed a deficiency of fluoride ions in tap water in almost all districts of the Belgorod region. Therefore, in order to avoid negative health effects, it can be recommended for consumption instead of

pre-conduit water is drinking table mineral waters, which meet the quality standards in terms of the content of fluoride ions (see Table 2).

The investigated mineral waters are characterized by a low content of iodide ions, the concentration of which is approximately 0.01-0.03 mg / L, which is closer to the lower limit of the physiological usefulness of drinking water and does not meet the quality standards for packaged drinking water of the highest category (0.04-0.06 mg / L). The lowest concentration of iodide ions (0.007 mg / l) is noted in the mineral water "Standard Belogorya".

A weak degree of iodine deficiency was also previously established for the water of CSPV. The consequence of iodine deficiency is thyroid disease (endemic goiter).

For comparison, we note that in the tap water of all regional centers of the Belgorod region there is an excess of the maximum permissible concentration of iron (0.3 mg / l)

Iron belongs to the essential trace elements necessary for human health. The function of hemoglobin containing iron (II) in oxygen transport is widely known. Iron is found in over 70 different enzymes. The negative impact of iron deficiency and excess on the human body is described in more detail in our previous publications.

The study of 12 types of prepackaged mineral waters produced in the Belgorod region allows us to give them the following assessment.

The investigated mineral waters belong to the group of slightly alkaline, soft, hydrocarbonate waters.

More than half of mineral waters are characterized by an insufficient content of calcium and magnesium ions, the concentration ratio of which is not optimal for human health.

The concentration of sulfate and chloride ions does not exceed generally accepted standards.

50% of mineral waters in terms of the content of fluoride ions meet the quality standards for waters of the highest category and the standards for the physiological usefulness of drinking water.

For all investigated mineral waters, a weak degree of iodine deficiency was established.

The concentration of total iron (II and III) does not exceed the maximum permissible value.

The "Path to the Top" mineral water can be considered optimal in terms of its cationic-anionic composition, all indicators of which, except for iodine deficiency, comply with the quality standards for packaged drinking water.

Bibliography

1. Nikanorov A.M. Hydrochemistry: textbook. - 2nd ed. - SPb: Gidrometeoizdat, 2001 .-- 444 p.

2. Posokhov E.V., Tolstikhin N.I. Mineral waters (medicinal, industrial and energy). - L .: Nedra, 1977 .-- 240 p.

3. Novikov Yu.V., Sayfutdinov M.M. Water and life on Earth. - M .: Nauka, 1981 .-- 184 p.

4. SanPiN 2.1.4. 1116-02 “Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control". - Moscow, 2002.

5. Plotnikov N.I. Groundwater is our wealth. - M .: Nedra, 1990 .-- 206 p.

6. Khrisanov V.A., Petin A.N., Yakovchuk M.M. Geological structure and minerals of the Belgorod region: textbook. allowance. - Belgorod: BelGU Publishing House, 2000 .-- 245 p.

7. Atlas "Natural resources and ecological state of the Belgorod region": educational reference cartographic manual / Ed. F.N. Lisetskiy. - Belgorod: BelGU Publishing House, 2005.-179 p.

8. State control of water quality. - M .: IPK. Publishing house of standards, 2001. - 698 p.

9. GOST 23268.3-78 “Mineral drinking waters, medicinal, medical-table and natural table. Methods for the determination of hydrocarbonate ions ", 1978.

10. GOST 4389-72 “Drinking water. Methods for determining the content of sulfate ions ", 1974.

11. GOST 23268.17-78 “Mineral drinking water, medicinal, table and natural table. Methods for the determination of chloride ions ", 1978.

12. GOST 4011-72 “Drinking water. Methods for measuring the mass concentration of total iron ",

13. Kissin I.G. The water is underground. - M .: Nauka, 1976 .-- 230 p.

14. General chemistry. Biophysical chemistry. Chemistry of biogenic elements / Ed. Yu.A. Ershova. -M .: Higher school, 2000 .-- 560 p.

15.http: //bydzdrav.ru/aboutwater/article1

16. Hygienic rationing of the minimum level of magnesium in drinking water / Yu.V. Novikov, S.I. Plitman, A.I. Levin, Yu.A. Noarov // Hygiene and Sanitation. - 1983. - No. 9. - S. 7-11.

17. Lugoi G.F. The chemical composition of drinking water and public health // Hygiene and sanitation. -1992. - No. 1. - S. 13-15.

18. Goldovskaya-Peristaya L.F., Peristy V.A., Shaposhnikov A.A. Hygienic assessment of the quality of drinking water in the centralized water supply system of the Belgorod region by some chemical indicators // Scientific Bulletin of BelGU. - 2008. - No. 3 (43). Ser. "Natural Sciences". Issue 6. -C. 140-146.

19. Evaluation of the quality of drinking water in the Belgorod region by chemical composition and properties / L.F. Goldovskaya-Peristaya, V.A. Peristyi, A.A. Shaposhnikov, E.A. Denisov // Scientific Bulletin of Bel-GU. - 2008. - No. 7 (47). Ser. "Natural Sciences". Issue 7. - S. 66-70.

20. SanPiN 2.1.4. 1074-01 “Drinking water. Hygienic requirements for water quality of centralized drinking water supply systems. Quality control". - Moscow, 2002

21. Wise I.V. On the influence of the mineral composition of drinking water on the health of the population (review) // Hygiene and sanitation. - 1999. - No. 1. - S. 15-18.

22. Human microelementosis: etiology, classification, organopathology / A.P. Avtsyn, A.A. Zhavoronkov, M.A. Risch, L.S. Strochkova. - M .: Medicine, 1991 .-- 496 p.

23. The environment of Russia at the turn of the millennium. Popular report on the state of the environment in Russia / I.A. Pankeev, N.G. Rybalsky, A.D. Dumnov et al. - M .: REFIA, NIA-Priroda, 2003. - 80 p.

CHEMICAL COMPOSITION OF MINERAL WATERS OF BELGOROD REGION

L.F. Goldovskaya-Peristaya, I.V. Indina, VA Peristy, M.N. Yapryntsev

Belgorod State National Research Uiversity, Pobedy St., 85, Belgorod, 308015, Russia

The chemical composition of 12 kinds prepacked mineral waters produced in the Belgorod region has been investigated. Activity of the solvated hydrogen ions, total hardness, content of calcium-, magnesium-, bicarbonate-, sulfate-, chloride-, fluoride-, iodide-ions and total ferrum (II and III) have been defined. These water quality indicators of mineral waters with those of water from centralized water supply system have been compared. Biochemical estimate of the results has been given.

Email: [email protected]

Key words: mineral water, cation-anion composition, water quality target, physiological usefulness of drinking water ..

1. Reservoirs and indicators of water quality

1.2. Indicators of the ecological state of water bodies and the quality of surface waters

1.2.4. Mineral composition of water

Mineralization- the total content of all mineral substances found in the chemical analysis of water; usually expressed in mg / dm 3 (up to 1000 mg / dm 3) and ‰ (ppm or thousandth with a mineralization of more than 1000 mg / dm 3).

Mineralization of natural waters, which determines their specific electrical conductivity, varies within wide limits (Table 7). Most rivers have mineralization from several tens of milligrams per liter to several hundred. Mineralization of groundwater and salt lakes varies in the range from 40–50 mg / dm 3 to 650 g / kg (the density in this case is already significantly different from unity). Mineralization of atmospheric precipitation ranges from 3 to 60 mg / dm 3.

Table 7

Classification of natural waters by mineralization

Many industries, agriculture, drinking water supply enterprises impose certain requirements on the quality of water, in particular, to mineralization, since waters containing a large amount of salt negatively affect plant and animal organisms, production technology and product quality, cause scale formation on the walls boilers, corrosion, soil salinization.

In accordance with the hygienic requirements for the quality of drinking water, the total mineralization should not exceed 1000 mg / dm 3. By agreement with the authorities of the Department of Sanitary and Epidemiological Supervision, for a water supply system that supplies water without appropriate treatment (for example, from artesian wells), an increase in mineralization up to 1500 mg / dm 3 is allowed).

The mineral composition of water is interesting in that it reflects the result of the interaction of water as a physical phase and the environment of life with other phases (environments): solid, i.e. coastal underlying, as well as soil-forming minerals and rocks; gaseous (with air) and moisture and mineral components contained in it. In addition, the mineral composition of water is due to a number of physicochemical and physical processes occurring in different environments - dissolution and crystallization, peptization and coagulation, sedimentation, evaporation and condensation, etc. in other environments, chemical reactions involving compounds of nitrogen, carbon, oxygen, sulfur, etc.

Two groups of mineral salts can be distinguished, usually found in natural waters (Table 8).

Table 8

The main components of the mineral composition of water

Component of the mineral composition of water	Maximum Allowable Concentration
Group 1
Cations:
Calcium (Ca 2+)
Sodium (Na +)
Magnesium (Mg 2+)
Anions
Bicarbonate (HCO 3)
Sulfate (SO 4 2)
Chloride (C1)
Carbonate (CO 3 2)
Group 2
Cations
Ammonium (NH 4 +)
Heavy metals (amount)	0.001 mmol / L
Total iron (sum of Fe 2+ and Fe 4+)
Anions
Nitrate (NO 3)
Orthophosphate (PO 4 3)
Nitrite (NO 2 )

As you can see from the table. 8, the main contribution to the mineral composition is made by the salts of the 1st group (they form the so-called "main ions"), which are determined in the first place. These include chlorides, carbonates, hydrocarbons, sulfates. The corresponding cations for the named anions are potassium, sodium, calcium, magnesium. Salts of the 2nd group must also be taken into account when assessing the quality of water, because each of them has an MPC value, although they make an insignificant contribution to the salinity of natural waters.

The concentration ratio of the main ions in water (in mg-eq / l) determines types of water chemistry. Depending on the predominant type of anions (> 25% equivalent, provided that the sums of mEq of anions and cations are taken equal to 50%, respectively, each), water of the hydrocarbonate class is distinguished (HCO 3 concentration> 25% equivalent of anions), sulfate (SO 4> 25% equiv.), Chloride (C1> 25% , eq.). Sometimes waters of mixed or intermediate types are also distinguished. Accordingly, among the cations, there are groups of calcium, magnesium, sodium or potassium waters.

Mineralization of water is of paramount importance in characterizing the chemical composition of waters. At the same time, water analyzes are carried out for the content of mineral components in different periods: for surface waters - during the winter low-water period, spring flood (peak), summer-autumn low-water period, summer-autumn flood; for waters of swampy areas - during the winter low-water period; spring flood, for soil waters - in winter low-water period, spring flood and summer-autumn low-water period.

The concentration of mineral salts dissolved in water is determined, as a rule, by chemical methods - titrimetric, colorimetric. The concentration of some components (for example, sodium and potassium cations) in water can be estimated by calculation methods, having data on the values ​​of the concentrations of other cations and anions.

Rigidity. Water hardness is a property of natural water, depending on the presence of mainly dissolved calcium and magnesium salts. Of all the salts related to hardness salts, hydrocarbonates, sulfates and chlorides are isolated. The total content of soluble calcium and magnesium salts is called overall rigidity... The total hardness is subdivided into carbonate due to the concentration of bicarbonates (and carbonates at pH 8.3) calcium and magnesium, and non-carbonate- concentration of calcium and magnesium salts of strong acids in water. Since when water is boiled (more precisely, at a temperature of more than 60 0 C), bicarbonates turn into carbonates that precipitate, carbonate hardness is called temporal or removable... The hardness remaining after boiling (due to chlorides or sulfates) is called permanent.

Water hardness is one of the most important properties of great importance in water use. If metal ions are found in water, forming insoluble salts of fatty acids with soap, then in such water it becomes difficult to form foam when washing clothes or washing hands, as a result of which a feeling of stiffness arises. Water hardness has a detrimental effect on pipelines when water is used in heating networks, and leads to the formation of scale. For this reason, special “softening” chemicals have to be added to the water.

Under natural conditions, ions of calcium, magnesium and other alkaline earth metals, which cause hardness, enter the water as a result of the interaction of dissolved carbon dioxide with carbonate minerals and other processes of dissolution and chemical weathering of rocks. The source of these ions is also microbiological processes occurring in soils in the catchment area, in bottom sediments, as well as wastewater from various enterprises.

Water hardness varies widely. Due to the fact that hardness salts are salts of different cations with different molecular weights, concentrations of hardness salts, or water hardness, they are measured in units of equivalent concentration - the amount of g-eq / l or meq / l. Water with a hardness less than 4 mEq / dm 3 is considered soft, from 4 to 8 mEq / dm 3 - medium hardness, from 8 to 12 mEq / dm 3 - hard and above 12 mEq / dm 3 - very tough. The total hardness ranges from units to tens, sometimes hundreds of meq / dm 3, and the carbonate hardness is up to 70–80% of the total hardness.

Usually, hardness due to calcium ions predominates (up to 70%); however, in some cases, magnesium hardness can reach 50-60%. The hardness of sea water and oceans is much higher (tens and hundreds of meq / dm 3). The hardness of surface waters is subject to significant seasonal fluctuations, usually reaching the highest value at the end of winter and the lowest during the flood period.

High hardness impairs the organoleptic properties of water, imparting a bitter taste to it and affecting the digestive organs.

The permissible value of the total hardness for drinking water and sources of centralized water supply is no more than
7 mEq / l (in some cases - up to 10 mEq / l), the limiting hazard indicator is organoleptic.

The proposed method for determining the total hardness as the total mass concentration of calcium and magnesium cations is based on the reaction of calcium and magnesium salts with a reagent - Trilon B (disodium salt of ethylenediaminetetraacetic acid):

where R is the radical of ethylenediaminetetraacetic acid.

The analysis is carried out in an ammonia buffer solution at pH 10.0-10.5 by the titrimetric method in the presence of a dark blue acid chromium indicator.

The total hardness (C rev) in mg-eq / l is calculated by the formula:

where: V TP is the volume of Trilon B solution consumed for titration, ml;

H is the concentration of the titrated solution of Trilon B, taking into account the correction factor, g-eq / l;

V A - volume of water taken for analysis, ml;

1000 - conversion factor of units of measurement from g-eq / l to mg-eq / l.

Determination of the total hardness of water

Equipment and reagents

Bath water; scissors; glass stick; 2 ml pipette or
5 ml with rubber bulb (medical syringe) and connecting tube; dropper pipette; bottle labeled "10 ml".

Distilled water; ammonia buffer solution; indicator solution chromium dark blue acid; Trilon B solution (0.05 g-eq / l).

Performing analysis

1. Pour 10 ml of the analyzed water into a bottle.

2. Add 6-7 drops of ammonia buffer solution and 4-5 drops of dark blue acid chromium indicator solution to the bottle with pipettes.

3. Seal the bottle hermetically and shake to mix.

4. Gradually titrate the contents of the bottle with Trilon B solution until the color at the equivalence point changes from wine red to bright blue. Shake the sample bottle periodically to mix the sample. Determine the volume of the solution consumed for titration of the total hardness (V coolant, ml).

5. Calculate the value of the total hardness (C cool) in mg-eq / l according to the formula: C cool = V cool × 5.

Note. After the color change, the sample must be kept for another 0.5 min. for the reaction to proceed completely, and then decide on the end of the titration (the color of the solution may recover somewhat. In this case, it is necessary to add some more Trilon B solution).

Calcium. The main sources of calcium input into surface waters are the processes of chemical weathering and dissolution of minerals, primarily limestone, dolomite, gypsum, calcium-containing silicates and other sedimentary and metamorphic
rocks.

Dissolution is facilitated by microbiological processes of decomposition of organic substances, accompanied by a decrease in pH.

Large amounts of calcium are carried out with wastewater from the silicate, metallurgical, glass, chemical industries and with wastewater from agricultural land, especially when calcium-containing mineral fertilizers are used.

A characteristic feature of calcium is the tendency to form rather stable supersaturated solutions of CaCO 3 in surface waters. The ionic form (Ca 2+) is characteristic only for low-mineralized natural waters. Quite stable complex compounds of calcium with organic substances contained in water are known. In some low-mineralized colored waters up to
90-100% of calcium ions can be bound by humic acids.

In river waters, the calcium content rarely exceeds 1 g / dm 3. Usually, however, its concentration is much lower.

The concentration of calcium in surface waters is subject to significant seasonal fluctuations. During the period of decrease in mineralization (in spring), calcium ions play a predominant role, which is associated with the ease of leaching of soluble calcium salts from the surface layer of soils and rocks.

MPC bp calcium is 180 mg / dm 3.

Quite stringent requirements for the calcium content are imposed on the waters feeding steam power plants, since in the presence of carbonates, sulfates and a number of other anions, calcium forms strong scale. Data on the content of calcium in waters are also necessary in solving issues related to the formation of the chemical composition of natural waters, their origin, as well as in the study of carbonate-calcium equilibrium.

The method for determining the mass concentration of the calcium cation (GOST 1030) is similar to the method for determining the total hardness with the Trilon B reagent, with the difference that the analysis is carried out in a highly alkaline medium (pH 12-13) in the presence of the indicator murexide.

The mass concentration of calcium is calculated from the titration results using the same formula. The determination of calcium is interfered with by carbonates and carbon dioxide removed from the sample upon acidification.

Determination of calcium

Equipment and reagents

Bath water; scissors; glass stick; 2 ml pipette or
5 ml with syringe and connecting tube; dropper pipette
(0.5 ml); bottle labeled "10 ml".

Indicator paper, universal; distilled water; indicator murexid in capsules (0.03 g each); ammonia buffer solution; sodium hydroxide solution (10%); hydrochloric acid solution (1: 100); Trilon B solution (0.05 g-eq / l).

For the preparation of solutions, see Appendix 3.

Performing analysis

1. Pour the analyzed water into a bottle marked "10 ml" up to the mark.

2. Next, the bicarbonate anion is removed from the solution. To do this, add a solution of hydrochloric acid (1: 100) dropwise to the bottle with vigorous stirring with a glass rod until the pH of the solution reaches 4-5 (with stirring, most of the carbon dioxide that interferes with the determination is also removed).

Control the pH value with universal indicator paper. 3. Add to the sample with a dropper pipette 13-14 drops (about 0.5 mg) of sodium hydroxide solution and the contents of one capsule (0.02-0.03 g) of murexide indicator. Stir the solution with a glass rod. 4. Then titrate with Trilon B solution using a 5 ml pipette on black background before the color transition at the equivalence point from orange to blue-violet. Determine the volume of Trilon B solution consumed for calcium titration (V CA, ml). 5. Calculate the mass concentration of calcium (C KA) in mg-eq / l according to the equation: With KA = V KA × 5.

Note. After the color change, the sample must be kept for another 0.5 min. for the reaction to proceed completely, and then decide on the end of the titration (the color of the solution may recover somewhat. In this case, it is necessary to add some more Trilon B solution).

Magnesium... Magnesium enters surface waters mainly due to the processes of chemical weathering and dissolution of dolomites, marls and other minerals. Significant amounts of magnesium can enter water bodies with wastewater from metallurgical, silicate, textile and other enterprises.

MPC bp of Mg 2+ ions is 40 mg / dm 3.

To determine the magnesium content in unpolluted surface and ground natural waters, as in most river waters, a calculation method can be used based on the difference between the results of determining the total hardness and the concentration of calcium cation. For the analysis of contaminated waters for magnesium content, it is necessary to use the direct determination of magnesium.

Determination of magnesium

The mass concentration of the magnesium cation (C mg) in mg / l is determined by the calculation method, making calculations using the formula:

where C coolant and C CA are the results of determining the total hardness (mg-eq / l) and the mass concentration of the calcium cation (mg / l), respectively; 0.05 is the conversion factor for the concentration of calcium cation in milligram-equivalent form; 12.16 is the equivalent mass of magnesium.

Round off the obtained result to whole numbers (mg / l).

Carbonates and hydrocarbons. The main source of hydrocarbonate and carbonate ions in surface waters are the processes of chemical weathering and dissolution of carbonate rocks such as limestones, marls, dolomites, for example:

Some of the hydrocarbonate ions come with precipitation and groundwater. Hydrocarbonate and carbonate ions are carried into reservoirs with wastewater from chemical, silicate, soda industries, etc.

With the accumulation of hydrocarbonate and especially carbonate ions, the latter can precipitate:

As noted above (in the "Alkalinity and Acidity" section), carbonates and bicarbonates are the components that determine the natural alkalinity of water. Their content in water is due to the processes of dissolution of atmospheric CO 2, the interaction of water with limestones in the adjacent soils and, of course, the vital processes of respiration of all aquatic organisms.

The determination of carbonate and bicarbonate anions is titrimetric and based on their reaction with hydrogen ions in the presence of phenolphthalein (in the determination of carbonate anions) or methyl orange (in the determination of bicarbonate anions) as indicators. Using these two indicators, it is possible to observe two points of equivalence: at the first point (pH 8.0-8.2) in the presence of phenolphthalein, the titration of carbonate anions is completely completed, and at the second (pH 4.1-4.5) - bicarbonate -anions. According to the results of titration, it is possible to determine the concentration in the analyzed solution of the main ionic forms that determine the consumption of acids (hydroxo, carbonate and bicarbonate anions ), as well as the values ​​of free and total alkalinity of water, because they are in stoichiometric dependence on the content of hydroxol, carbonate and hydrocarbonate anions. For titration, titrated solutions of hydrochloric acid are usually used with an accurately known concentration value of 0.05 g-eq / l or 0.1 g-eq / l.

The determination of hydrocarbonate anions is based on the reaction:

CO 3 2- + H + = HCO 3.

The presence of the carbonate anion in analytically determined concentrations is possible only in waters with a pH of more than 8.0-8.2. In the case of the presence of hydroxo-anions in the analyzed water, the neutralization reaction also occurs during the determination of carbonates:

OH - + H + = H 2 O.

The determination of hydrocarbonate anions is based on the reaction:

HCO 3 - + H + = CO 2 + H 2 O.

Thus, during titration with phenolphthalein, the anions OH - and CO 3 2- participate in the reaction with acid, and with titration with respect to methyl orange - OH -, CO 3 2- and HCO 3 -.

The value of carbonate hardness is calculated taking into account the equivalent masses of carbonate and bicarbonate anions participating in the reactions.

When analyzing natural carbonate waters, the correctness of the results obtained depends on the amount of acid consumption for titration with respect to phenolphthalein and methyl orange. If titration in the presence of phenolphthalein usually does not cause difficulties, because there is a color change from pink to colorless, then in the presence of methyl orange, when the color changes from yellow to orange, it is sometimes quite difficult to determine the end of the titration. This can lead to a significant error in determining the volume of acid consumed for titration. In these cases, for a clearer identification of the end of the titration, the determination is useful in the presence of a control sample, for which the same portion of the analyzed water (in the second bottle) is placed next to the titrated sample, adding the same amount of indicator.

As a result of the titration of carbonate and bicarbonate, which can be performed both in parallel in different samples, and sequentially in the same sample, in order to calculate the concentration values, it is necessary to determine the total amount of acid (V 0) in milliliters consumed for titration of carbonate (VK) and bicarbonate (V GK). It should be borne in mind that when determining the consumption of acid for titration with respect to methyl orange (V MO), sequential titration of both carbonates and hydrocarbons occurs. For this reason, the resulting volume of acid V MO contains a corresponding proportion due to the presence in the initial sample of carbonates that have passed after the reaction with the hydrogen cation into bicarbonates, and does not fully characterize the concentration of bicarbonates in the original sample. Consequently, when calculating the concentrations of the main ionic forms that determine the consumption of acid, it is necessary to take into account the relative consumption of acid during titration for phenolphthalein (V ph) and methyl orange (V mo). Consider several possible options, comparing the values ​​of V f and V MO.

1. V f = 0. Carbonates, as well as hydroxo-anions are absent in the sample, and the consumption of acid during titration with respect to methyl orange can only be due to the presence of hydrocarbonates.

2.V f ¹ 0, and 2V f< V мо. В исходной пробе отсутствуют гидроксо-анионы, но присутствуют и гидрокарбонаты, и карбонаты, причем доля последних эквивалентно оценивается как V К = 2V Ф, а гидрокарбонатов – как V ГК = V МО – 2V Ф.

3.2 V Ф = V MO. There are no hydrocarbonates in the original sample, and the consumption of acid is due to the content of almost only
carbonates, which are quantitatively converted into bicarbonates. This explains the doubled, in comparison with U f, the consumption of acid V MO.

4.2 V Ф> V MO. In this case, there are no hydrocarbonates in the initial sample, but not only carbonates are present, but also other acid-consuming anions, namely, hydroxo-anions. In this case, the content of the latter is equivalent to V it = 2V f - V mo. The carbonate content can be calculated by compiling and solving the system of equations:

5. V Ф = V MO. The original sample lacks both carbonates and hydrocarbonates, and acid consumption is due to the presence of strong alkalis containing hydroxo anions.

The presence of free hydroxo-anions in noticeable amounts (cases 4 and 5) is possible only in wastewater.

The mass concentrations of anions (not salts!) Are calculated on the basis of the equations for the reactions of acid consumption by carbonates (C to) and bicarbonates (C g) in mg / L according to the formulas:

where V to and V gk is the volume of hydrochloric acid solution consumed for titration of carbonate and bicarbonate, respectively, ml; H is the exact concentration of a titrated solution of hydrochloric acid (normality), g-eq / l; V A - volume of water sample taken for analysis, ml; 60 and 61 - equivalent weight of carbonate and bicarbonate anions, respectively, in the corresponding reactions; 1000 - conversion factor of units of measurement.

The results of titration for phenolphthalein and methyl orange make it possible to calculate the alkalinity of water, which is numerically equal to the number of acid equivalents consumed for titration of a 1 liter sample. At the same time, the consumption of acid during titration for phenolphthalein characterizes free alkalinity, and for methyl orange - total alkalinity, which is measured in meq / l. The alkalinity indicator is used in Russia, as a rule, in the study of wastewater. In some other countries (USA, Canada, Sweden, etc.), alkalinity is determined when assessing the quality of natural waters and is expressed in mass concentration in the equivalent of CaCO 3.

It should be borne in mind that when analyzing waste and polluted natural waters, the results obtained do not always correctly reflect the values ​​of free and total alkalinity, because in water, in addition to carbonates and bicarbonates, compounds of some other groups may be present (see "Alkalinity and acidity").

Equipment and reagents

2 ml or 5 ml pipette with rubber bulb (medical syringe) and connecting tube; dropper pipette, bottle labeled "10ml".

Methyl orange indicator solution 0.1%; phenolphthalein indicator solution; titrated hydrochloric acid solution (0.05 g-eq / l).

For the preparation of solutions, see Appendix 3.

Performing analysis

1. Titration of the carbonate anion

1. Pour the analyzed water into the bottle up to the mark (10 ml). 2. Add 3-4 drops of phenolphthalein solution with a pipette. Note. In the absence of staining of the solution or with a slightly pink color, it is considered that the carbonate anion is absent in the sample (the pH of the sample is less than 8.0-8.2). 3. Gradually titrate the sample using a measuring syringe with a tip or a measuring pipette with hydrochloric acid solution (0.05 g-eq / l) until the color turns pale to slightly pink, and determine the volume of hydrochloric acid solution consumed for titration by phenolphthalein (U f, ml). 2. Titration of the bicarbonate anion 4. Pour the analyzed water into the bottle up to the mark (10 ml) or use the solution after determining the carbonate anion.

5. Add 1 drop of Methyl Orange solution with a pipette.

Note. For a clearer definition of the end of the titration, the determination is useful in the presence of a control sample, for which the same portion of the analyzed water (in the second bottle) is placed next to the titrated sample, adding the same amount of indicator.

6. Gradually titrate the sample using a measuring syringe with a tip with a hydrochloric acid solution (0.05 g-eq / L) with stirring until the color turns from yellow to pink, determining the total volume of the solution used for the methyl orange titration.
(V mo, ml). When using a solution after determining the carbonate anion, it is necessary to determine the total volume consumed for titration of carbonate and bicarbonate.

Necessarily stir titration solution!

Determine the end of the titration using the control sample.

3. Determination of ionic forms causing acid consumption for titration

Depending on the ratio between the amounts of acid consumed for titration for phenolphthalein (V f) and methyl orange (V mo), according to table. 9 select the appropriate option for calculating the ionic forms that determine the acid consumption in the titration. Leave the solution after titration of the carbonate anion for further determination of the mass concentration of the bicarbonate anion in it.

Table 9

Determination of ionic forms causing consumptionacid
for titration

Ratio between V f and V mo	Contribution of ionic forms to consumption
2V f< V мо
2V f> V mo	2V f - V mo

The approximate order of using the table. 9. Follow the steps and answer the following questions.

1. Does the solution have zero free alkalinity? (i.e., when phenolphthalein is added, the solution does not acquire color or turns slightly pink). If yes, then acid consumption is due to the presence of hydrocarbonates only - see column 1 of Table 9.

2. Is the acid consumption for phenolphthalein titration equal to the total acid consumption for the titration? If yes, then the consumption of acid is due to the presence of only hydroxyl anions - see column 5 of table. nine.

3. Multiply the obtained acid consumption for phenolphthalein titration by 2 and compare the product with the total acid consumption for columns 2-4 of Table. 9. In each case, determine the contribution of the ionic forms present to the acid intake.

Calculation example... In the first sample, the amount of acid solution consumed for titration for phenolphthalein was determined
(V = 0.10 ml). In the second sample, the amount of acid consumed for methyl orange titration was determined: V MO = 0.25 ml. We compare the values. Consequently, the sample contains both carbonate and bicarbonate anions, and the consumption of acid by carbonates is, and by bicarbonates - V gc = V mo -2V f = 0.25-0.20 = 0.05 ml.

4. Check the calculation results: the sum of acid intake for all three forms should be equal to the total acid intake.

4. Calculation of the mass concentration of carbonate and bicarbonate anions

1. Determine from the table. 9 the contribution of various ionic forms to the consumption of acid during titration (V k, V gk).

2. Calculate the mass concentration of carbonate anion (C to) in mg / l according to the formula: C to = V to 300.

Round up the result to whole numbers.

3. Calculate the mass concentration of the bicarbonate anion (C gk) in mg / l using the formula: C gk = V gk 305. Round the result to whole numbers.

5. Calculation of carbonate hardness

Determine the carbonate hardness (W c) in mg-eq / l using the formula:

Zh k = C k 0.0333 + C gk 0.0164.

6. Calculation of alkalinity

Meaning free Alkalinity (Schw) in mg-eq / l, calculate by the formula:

Sch sv = V f 5.

Meaning total alkalinity(SHO) in mg-eq / l, calculate by the equation:

Ш о = V MO 5

The magnitude carbonate hardness for natural surface waters, it is taken to be equal to the total alkalinity (mg-eq / l).

Biogenic elements. Biogenic elements (biogens) are traditionally considered to be elements that are included, in significant quantities, in the composition of living organisms. The range of elements classified as biogenic is quite wide, these are nitrogen, phosphorus, sulfur, iron, calcium, magnesium, potassium, etc.

The issues of water quality control and ecological assessment of water bodies have introduced a broader meaning into the concept of biogenic elements: they include compounds (more precisely, water components), which are, firstly, the waste products of various organisms and, secondly, are "building materials" for living organisms. First of all, these include nitrogen compounds (nitrates, nitrites, organic and inorganic ammonium compounds), as well as phosphorus (orthophosphates, polyphosphates, organic phosphoric acid esters, etc.).

Nitrates. The presence of nitrate ions in natural waters is associated with:

With in-water processes of nitrification of ammonium ions in the presence of oxygen under the action of nitrifying bacteria;

· Atmospheric precipitation, which absorb nitrogen oxides formed during atmospheric electrical discharges (the concentration of nitrates in atmospheric precipitation reaches 0.9 - 1 mg / dm 3);

· Industrial and domestic wastewater, especially after biological treatment, when the concentration reaches 50 mg / dm 3;

· With runoff from agricultural land and with waste water from irrigated fields on which nitrogen fertilizers are applied.

The main processes aimed at lowering the concentration of nitrates are their consumption by phytoplankton and denitrifying bacteria, which, with a lack of oxygen, use the oxygen of nitrates to oxidize organic matter.

In surface waters, nitrates are in dissolved form. The concentration of nitrates in surface waters is subject to noticeable seasonal fluctuations: the minimum during the growing season, it increases in autumn and reaches a maximum in winter, when, with a minimum consumption of nitrogen, organic matter decomposes and the transition of nitrogen from organic to mineral forms. The amplitude of seasonal fluctuations can serve as one of the indicators of the eutrophication of a water body.

With prolonged use of drinking water and food products containing significant amounts of nitrates (from 25 to 100 mg / dm 3 in nitrogen), the concentration of methemoglobin in the blood increases sharply. Methemoglobinemia is extremely difficult in infants (first of all, artificially fed milk formulas prepared in water with an increased - about 200 mg / dm 3 - nitrate content) and in people suffering from cardiovascular diseases. Especially in this case, groundwater and the wells fed by it are dangerous, since nitrates in open reservoirs are partially consumed by aquatic plants.

The presence of ammonium nitrate at concentrations of the order of 2 mg / dm 3 does not cause disruption of biochemical processes in the reservoir; the subthreshold concentration of this substance, which does not affect the sanitary regime of the reservoir, is 10 mg / dm 3. Damaging concentrations of nitrogen compounds (primarily ammonium) for various fish species are on the order of hundreds of milligrams per 1 dm 3 of water.

In human exposure, the primary toxicity of the nitrate ion itself is distinguished; secondary, associated with the formation of nitrite ion, and tertiary, due to the formation of nitrites and amines of nitrosamines. The lethal dose of nitrates for humans is
8-15 g; permissible daily intake according to the FAO / WHO recommendations - 5 mg / kg body weight.

Along with the described effects of exposure, an important role is played by the fact that nitrogen is one of the primary biogenic (necessary for life) elements. This is the reason for the use of nitrogen compounds as fertilizers, but, on the other hand, this is related to the contribution of nitrogen removed from agricultural lands to the development of eutrophication processes (uncontrolled growth of biomass) of water bodies. So, from one hectare of irrigated land, 8-10 kg of nitrogen is carried into water systems.

Nitrates are salts of nitric acid and are commonly found in water. The nitrate anion contains a nitrogen atom in the maximum oxidation state "+5". Nitrate-forming (nitrate-fixing) bacteria convert nitrite to nitrate under aerobic conditions. Under the influence of solar radiation, atmospheric nitrogen (N 2) is also converted mainly into nitrates through the formation of nitrogen oxides. Many mineral fertilizers contain nitrates, which, if applied excessively or irrationally to the soil, lead to water pollution. Surface runoff from pastures, cattle yards, dairy farms, etc. are also sources of nitrate pollution.

The increased content of nitrates in the water can serve as an indicator of the pollution of the reservoir as a result of the spread of fecal or chemical pollution (agricultural, industrial). Sewers rich in nitrate waters deteriorate the quality of water in the reservoir, stimulating the massive development of aquatic vegetation (primarily blue-green algae) and accelerating eutrophication reservoirs. Drinking water and food containing an increased amount of nitrates (Table 10) can also cause illness, especially in infants (so-called methemoglobinemia). As a result of this disorder, the transport of oxygen with blood cells deteriorates and the "blue baby" syndrome (hypoxia) occurs. At the same time, plants are not as sensitive to an increase in nitrogen content in water as phosphorus.

Table 10

Values ​​of maximum permissible concentrations of nitrates
for vegetables and fruits, mg / kg

The culture			The culture
Leafy vegetables			Potato
Sweet pepper			Early cabbage
Table grapes			Beetroot
			Onion

The proposed method for the determination of nitrates is based on the ability of salicylic (orthohydroxybenzoic) acid in the presence of concentrated sulfuric acid to enter into a nitration reaction with the formation of nitrosalicylic acid, which forms a yellow-colored salt in an alkaline medium.

The determination is interfered with by the chloride anion at a mass concentration of more than 500 mg / l and iron compounds at a mass concentration of more than
0.5 mg / l. They are freed from the influence of iron compounds by adding Rochelle's salt (salt of tartaric acid, potassium-sodium tartrate KNaC 4 H 4 O 6 4H 2 O); when the concentration of chlorides is more than 500 mg / l, the analyzed water is diluted and the determination is repeated.

MPC of nitrates in water of reservoirs and drinking water is 45 mg / l (or 10 mg / l for nitrogen), the limiting hazard indicator is sanitary and toxicological.

Equipment and reagents

Bath water; scissors; glass stick; 2 ml or 5 ml pipette with rubber bulb (medical syringe) and connecting tube; dropper pipette; bottle labeled "10ml"; a glass of 25-50 ml for evaporation. Protective glasses; rubber gloves.

Distilled water; concentrated sulfuric acid; sodium hydroxide solution (20%) aqueous; salicylic acid solution (10%) alcohol; Rochelle salt (potassium-sodium tartrate) in capsules of 0.1 g.

Control scale of color samples for the determination of nitrate anion (0.0; 5.0; 15; 30; 50 mg / l) from the test kit or prepared independently.

Attention! This definition uses corrosive substances - concentrated sulfuric acid and strong hydroxide solution sodium! It is necessary to work with them on a pallet in rubber gloves and goggles, being careful. It is unacceptable for the solutions to get into the eyes, on the skin, clothes, furniture.

Performing analysis

1. Pipette 1.0 ml of the analyzed water into the evaporation beaker. If the water contains iron compounds in a concentration of more than 0.5 mg / l, the contents of one capsule (0.1 g) of Rochelle salt are also added to the glass.

2. Evaporate the contents of the glass to dryness in a boiling water bath for 10-15 minutes.

3. Cool the glass to room temperature for
5-10 minutes

4. Add 4-5 drops of salicylic acid solution to the glass with a dropper pipette so that the entire dry residue is moistened.

5. Add 26-27 drops of concentrated sulfuric acid (about 0.5 ml) with another pipette.

Use caution when adding concentrated sulfuric to islots! Work should be done in goggles and rubber gloves weaving!

6. Mix dry residue with acid with a glass rod and rub it along the bottom and sides of the glass.

7. Without removing the stick from the glass, leave its contents for 5 minutes.

8. Add 3-4 ml of distilled water with a pipette so that the inside of the glass is washed.

9. Add 4-5 ml of 20% sodium hydroxide solution to the contents of the beaker. (For dosage of sodium hydroxide solution it is convenient to use a tube labeled "5 ml"). If there are nitrate anions in the analyzed water, the solution in the glass immediately turns yellow.

Use caution when adding hydroxy solution yes sodium! Wear protective goggles and rubber gloves!

10. Pour the contents of the glass on a glass rod into a bottle marked "10 ml", rinse the glass and the rod with small portions of distilled water and bring the volume of the solution in the bottle to 10 ml.

Note. If there is a precipitate (basic magnesium salts), leave the solution to settle for a few minutes.

11. Compare the color of the solution in the bottle with the control scale of the color samples on a white background. For the result of the analysis, take the value of the concentration of nitrate anions in mg / L of the sample on the scale that most closely matches the color of the resulting solution.

If the color of the contents of the flask for colorimetry turns out to be more intense than the extreme sample (50 mg / l), the analyzed water is diluted 5 times with distilled water and the determination is repeated. When calculating the results, take into account the degree of dilution of the sample.

Analysis accuracy control

Accuracy control in the determination of nitrates is carried out using control solutions (see Appendix 1) or using a verified (exemplary) nitrate meter.

Ammonium. The content of ammonium ions in natural waters varies in the range from 10 to 200 μg / dm 3 in terms of nitrogen. The presence of ammonium ions in unpolluted surface waters is mainly associated with the processes of biochemical degradation of protein substances, deamination of amino acids, and the decomposition of urea under the action of urease. The main sources of ammonium ions entering water bodies are livestock farms, household wastewater, surface runoff from agricultural lands in the case of using ammonium fertilizers, as well as wastewater from food, coke-chemical, timber-chemical and chemical industries. Industrial effluents contain up to
1 mg / dm 3 of ammonium, in household waste water - 2-7 mg / dm 3; with domestic wastewater, up to 10 g of ammonium nitrogen (per inhabitant) is supplied to the sewer systems daily.

With the transition from oligotrophic to meso- and eutrophic water bodies, both the absolute concentration of ammonium ions and their share in the total balance of bound nitrogen increase.

The presence of ammonium in concentrations of the order of 1 mg / dm 3 reduces the ability of fish hemoglobin to bind oxygen. Signs of intoxication - agitation, convulsions, the fish rushing about in the water and jumping to the surface. The mechanism of toxic action is excitation of the central nervous system, damage to the gill epithelium, hemolysis (rupture) of erythrocytes. The toxicity of ammonium increases with increasing pH of the medium. The ammonium content in reservoirs with different degrees of pollution is given in table. eleven.

Table 11

Pollution degree (classes of water bodies)	Ammonium nitrogen, mg / dm 3
Very clean
Moderately polluted
Contaminated
Very dirty

The increased concentration of ammonium ions can be used as an indicator reflecting the deterioration of the sanitary state of a water body, the process of pollution of surface and ground waters, primarily, domestic and agricultural wastewater.

Ammonium compounds contain a nitrogen atom in the minimum oxidation state "-3". Ammonium cations are a product of microbiological decomposition of animal and plant proteins. The ammonium formed in this way is again involved in the process of protein synthesis, thereby participating in the biological circulation of substances (nitrogen cycle). For this reason, ammonium and its compounds are usually present in low concentrations in natural waters.

There are two main sources of ammonia pollution in the environment. Ammonium compounds in large quantities are included in the composition of mineral and organic fertilizers, the excessive and improper use of which leads to the pollution of water bodies. In addition, ammonium compounds are present in significant quantities in sewage (feces). Sludge that is not properly disposed of can penetrate into groundwater or be washed off by surface drains into water bodies. Runoff from pastures and places of accumulation of livestock, sewage from livestock complexes, as well as domestic and household wastewater always contain large amounts of ammonium compounds. Dangerous contamination of groundwater by household, fecal and domestic wastewater occurs when the sewerage system is depressurized. For these reasons, an increased content of ammonium nitrogen in surface waters is usually a sign of household and fecal pollution.

The proposed method for determining the mass concentration of the ammonium cation (given in GOST 1030) is based on its reaction with Nessler's reagent with the formation of a compound colored in an alkaline medium in a yellow color:

The interfering influence of iron is eliminated by adding to the sample Rochelle salt: КСОО (СНОН) СООНАа.

The concentration of ammonium cations is determined by a visual colorimetric method, comparing the color of the solution with a control scale of color samples.

Maximum concentration limit of ammonia and ammonium ions in water of reservoirs is 2.6 mg / l (or 2.0 mg / l for ammonium nitrogen). The limiting hazard indicator is general sanitary.

Equipment and reagents

Scissors, 2 ml pipette, colorimetric tube with label
"5 ml", a medical syringe with a connecting tube.

Nessler's reagent, Rochelle salt in capsules of 0.1 g.

Control scale of color samples for the determination of ammonium cation (0; 0.2; 0.7; 2.0; 3.0 mg / l) from the test kit or prepared independently.

For the preparation of solutions, see Appendix 3.

Analysis

1. Pour the water to be analyzed into the colorimetric tube up to the 5 ml mark.

2. Add the contents of one capsule (about 0.1 g) of Rochelle salt to the water and add 1.0 ml of Nessler's reagent with a pipette. Mix the contents of the tube by shaking.

3. Leave the mixture for 1-2 minutes. to complete the reaction.

4. Compare the color of the solution in the bottle against the white background with the control scale of the color samples.

Analysis accuracy control

The control of the accuracy of the analysis in the determination of ammonium is carried out using control solutions with a known content of ammonium cations (see Appendix 1) or a verified (exemplary) device for measuring the concentration of ammonium by the potentiometric method.

Nitrite. Nitrites represent an intermediate stage in the chain of bacterial processes of ammonium oxidation to nitrates (nitrification - only under aerobic conditions) and, on the contrary, the reduction of nitrates to nitrogen and ammonia (denitrification - with a lack of oxygen). Such redox reactions are typical for aeration stations, water supply systems and natural waters proper. In addition, nitrites are used as corrosion inhibitors in the process of water treatment of process water and therefore can get into the systems of domestic drinking water supply. The use of nitrites for food preservation is also widely known.

In surface waters, nitrites are dissolved. In acidic waters, small concentrations of nitrous acid (HNO 2) (not dissociated into ions) may be present. An increased content of nitrites indicates an intensification of the processes of decomposition of organic substances under conditions of slower oxidation of NO 2 - into NO 3 -, which indicates the pollution of the water body, i.e. is an important sanitary indicator.

Seasonal fluctuations in nitrite content are characterized by their absence in winter and their appearance in spring during the decomposition of inanimate organic matter. The highest concentration of nitrites is observed at the end of summer; their presence is associated with the activity of phytoplankton (the ability of diatoms and green algae has been established to reduce nitrates to nitrites). In autumn, the nitrite content decreases.

One of the features of the distribution of nitrites over the depth of a water body are well-defined maxima, usually near the lower boundary of the thermocline and in the hypolimnion, where the oxygen concentration decreases most sharply.

In accordance with the requirements of the global environmental monitoring system (GEMS / GEMS), nitrite and nitrate ions are included in the programs of mandatory monitoring of the composition of drinking water and are important indicators of the degree of pollution and trophic status of natural water bodies.

Nitrite, due to its ability to convert to nitrate, is usually absent in surface waters. Therefore, the presence in the analyzed water of an increased content of nitrites indicates water pollution, taking into account the partially transformed nitrogenous compounds from one form to another.

The proposed method for determining the mass concentration of nitrite anion corresponds to that given in GOST 1030. The method is based on the reaction of a nitrate anion in a nitrous acid medium with a Griss reagent (a mixture of sulfanilic acid and 1-naphthylamine). In this case, diazotization and azo coupling reactions occur, as a result of which an azo compound (azo dye) is formed, which has a purple color.

The concentration of nitrite anions is determined by a visual colorimetric method, comparing the color of the solution with a control scale of color samples.

Reagents and equipment

Scissors, colorimetric test tube labeled "5 ml". Grissa reagent in capsules of 0.05 g.

Control scale of color samples for the determination of nitrite anion (0; 0.02; 0.10; 0.50; 1.0 mg / l) from the test kit or prepared independently.

For the preparation of the Griss reagent see Appendix 3.

Performing analysis

1. Pour the water to be analyzed into the colorimetric tube up to the 5 ml mark.

2. Add the contents of one capsule (about 0.05 g) of Griss reagent to the test tube. Mix the contents of the tube by shaking until the mixture is dissolved.

3. Leave the tube for 20 minutes. to complete the reaction.

4. Perform visual colorimetry on the sample. Compare the color of the solution in the test tube on a white background with the control scale of the color samples.

Analysis accuracy control

The control of the accuracy of the analysis in the determination of nitrites is carried out using control solutions with a known content of the nitrite anion (see Appendix 1) or using a verified (exemplary) nitrite meter by the potentiometric method.

Total nitrogen... Total nitrogen is understood as the sum of mineral and organic nitrogen in natural waters.

The amount of mineral nitrogen... The sum of mineral nitrogen is the sum of ammonium, nitrate and nitrite nitrogen.

An increase in the concentration of ammonium and nitrite ions usually indicates fresh contamination, while an increase in nitrate content indicates contamination in the past. All forms of nitrogen, including gaseous ones, are capable of mutual transformations.

Ammonia... In natural water, ammonia is formed during the decomposition of nitrogen-containing organic substances. Let's well dissolve in water to form ammonium hydroxide.

Phosphates and total phosphorus. Total phosphorus is understood as the sum of mineral and organic phosphorus. Just as for nitrogen, the exchange of phosphorus between its mineral and organic forms, on the one hand, and living organisms, on the other, is the main factor determining its concentration. In natural and waste waters, phosphorus can be present in different forms. In a dissolved state (sometimes they say - in the liquid phase of the analyzed water), it can be in the form of orthophosphoric acid (H 3 PO 4) and its anions (H 2 PO 4 -, HPO 4 2-, PO 4 3-), in the form of meta -, pyro- and polyphosphates (these substances are used to prevent the formation of scale, they are also included in detergents). In addition, there are various organophosphorus compounds - nucleic acids, nucleoproteins, phospholipids, etc., which can also be present in water, being the products of vital activity or decomposition of organisms. Certain pesticides are also classified as organophosphates.

Phosphorus can also be contained in an undissolved state (in the solid phase of water), being present in the form of poorly soluble phosphates suspended in water, including natural minerals, protein, organic phosphorus-containing compounds, the remains of dead organisms, etc. Phosphorus in the solid phase in natural water bodies is usually found in bottom sediments, however, can occur, and in large quantities, in waste and polluted natural waters. The forms of phosphorus in natural waters are presented in table. 12.

The concentration of total dissolved phosphorus (mineral and organic) in unpolluted natural waters varies from 5 to
200 μg / dm 3.

Table 12

Forms of phosphorus in natural waters

Chemical forms P		Filterable (dissolved)
		Total Dissolved Phosphorus	Total phosphorus in particles
Orthophosphates	Total dissolved and suspended phosphorus	Dissolved orthophosphates	Orthophosphates in particles
Acid hydrolyzed phosphates	Total dissolved and suspended acid hydrolyzable phosphates	Dissolved acid hydrolyzable phosphates	Acid hydrolyzable phosphates in particles
Organic phosphorus	Total dissolved and suspended organic phosphorus	Dissolved organic phosphorus	Organic phosphorus in particles

Phosphorus is the most important biogenic element, most often limiting the development of the productivity of water bodies. Therefore, the intake of excess phosphorus compounds from the catchment in the form of mineral fertilizers with surface runoff from fields (0.4-0.6 kg of phosphorus is removed from a hectare of irrigated land), with runoff from farms (0.01-0.05 kg / day per one animal), with unfinished or untreated domestic wastewater (0.003-0.006 kg / day per inhabitant), as well as with some industrial waste, leads to a sharp uncontrolled increase in the plant biomass of a water body (this is especially typical for stagnant and low-flowing water bodies). There is a so-called change in the trophic status of the reservoir, accompanied by the restructuring of the entire aquatic community and leading to the predominance of putrefactive processes (and, accordingly, an increase in turbidity, salinity, and the concentration of bacteria).

One likely aspect of the eutrophication process is the growth of blue-green algae (cyanobacteria), many of which are toxic. The substances secreted by these organisms belong to the group of phosphorus and sulfur-containing organic compounds (nerve poisons). The action of toxins of blue-green algae can manifest itself in the occurrence of dermatoses, gastrointestinal diseases; in especially severe cases - when a large mass of algae enters the body - paralysis may develop.

In accordance with the requirements of the global environmental monitoring system (GEMS / GEMS), the determination of the total phosphorus content (dissolved and suspended, in the form of organic and mineral compounds) is included in the compulsory observation programs for the composition of natural waters. Phosphorus is the most important indicator of the trophic status of natural reservoirs. The main form of inorganic phosphorus at pH values ​​of the reservoir above 6.5 is the ion HPO 4 2 - (about 90%). In acidic waters, inorganic phosphorus is present mainly in the form of H 2 PO 4 -.

The content of phosphorus compounds is subject to significant seasonal fluctuations, since it depends on the ratio of the intensity of the processes of photosynthesis and biochemical oxidation of organic substances. The minimum concentrations of phosphates in surface waters are usually observed in spring and summer, maximum - in autumn and winter, in sea waters - in spring and autumn, summer and winter, respectively.

The general toxic effect of phosphoric acid salts is possible only at very high doses and is most often due to impurities of fluorine.

Inorganic dissolved and suspended phosphates are colorimetrically determined without preliminary sample preparation.

Polyphosphates... Polyphosphates can be described by the following chemical formulas:

Me n (PO 3) n, Me n + 2 P n O 3n + 1, Me n H 2 P n O 3n + 1.

Polyphosphates are used for water softening, fiber degreasing, as a component of washing powders and soaps, corrosion inhibitor, catalyst, in the food industry.

Polyphosphates have low toxicity. The toxicity of polyphosphates is due to their ability to form complexes with biologically important ions, especially calcium.

Phosphates are determined, as a rule, by the colorimetric method (GOST 18309, ISO 6878) by reaction with ammonium molybdate in an acidic medium:

The resulting complex, a yellow product, then under the action of a reducing agent - tin (II) chloride - turns into an intensely colored blue dye of a complex composition - "molybdenum blue". The concentration of orthophosphates in the analyzed water is determined by the color of the sample, visually comparing it with the color of the samples on a control scale or by measuring the optical density of the samples using a photocolorimeter.

Of all the phosphates present in water, only orthophosphates directly enter this reaction. To determine polyphosphates, they must first be converted into orthophosphates by acid hydrolysis in the presence of sulfuric acid. Many phosphoric acid esters can also be determined after acid hydrolysis under the same conditions as polyphosphates. The acid hydrolysis reaction using pyrophosphate as an example proceeds as follows:

Na 4 Р 2 О 7 + 2Н 2 SO 4 + Н 2 О = 2Н 3 РО 4 + 4Na + + 2SO 4 2-.

Some phosphorus-containing organic compounds can be identified only after their mineralization, sometimes also called "wet combustion". Mineralization of phosphorus-containing organic compounds is carried out by boiling the sample with the addition of acid and a strong oxidizing agent - persulfate or hydrogen peroxide. In the case of using potassium persulfate for this purpose, the reaction proceeds according to the equation:

where R and R 1 are organic fragments.

Mineralization leads to the transformation into orthophosphates of all, even sparingly soluble, forms of phosphates in water. Thus, the content is determined total phosphorus in any water (this indicator can be determined both for dissolved phosphates and for insoluble phosphorus compounds). However, for natural waters that do not contain or contain an insignificant amount of difficult-to-hydrolyze phosphates in the solid phase, mineralization is usually not required, and the result obtained from the analysis of a hydrolyzed sample can, with a good approximation, be taken as the total phosphorus content.

The influence of some impurities that may be present in wastewater - silicates (more than 50 mg / l), iron (III) compounds (more
1 mg / L), sulfides and hydrogen sulfide (more than 3 mg / L), reduces the accuracy of the analysis, which is eliminated by adding special reagents to the sample that are part of the test kit, or by changing the sample processing operations.

The possible influence of nitrites (up to 25 mg / l) is eliminated by adding to the sample a solution for their binding (sulfamic acid solution). Large amounts of chlorides, nitrites, chromates, arsenates, tannins interfere with the analysis.

When analyzing phosphates in a hydrolyzed sample, the sum of orthophosphates and polyphosphates is directly determined; the concentration of polyphosphates is calculated as the difference between the results of the analysis of a hydrolyzed and non-hydrolyzed sample. Hydrolysis of polyphosphates also occurs during mineralization, because it is carried out in a highly acidic environment.

MPC of polyphosphates (tripolyphosphate and hexametaphosphate) in water bodies is 3.5 mg / l in terms of orthophosphate anion PO 4 3-, the limiting hazard indicator is organoleptic.

The range of determined concentrations of orthophosphates in water for visual colorimetric determination is from 0.2 to 7.0 mg / l, with photometric determination - 0.001 - 0.04 mg / l. Determination by the visual colorimetric method is also possible when the concentration of orthophosphates is more than 7.0 mg / l after appropriate dilution of the sample with pure water.

Equipment and reagents

Heat-resistant conical flask (Erlenmeyer) 150 ml with a thin section, a graduated measuring bottle (5.10.20 ml) with a stopper, a reflux condenser with a thin section, boiling points (glass capillaries, silica gel grains), a volumetric flask with a capacity of 50 ml, an electric stove with closed heating element, dropper pipette, porcelain cup on
200-500 ml, 1 ml medical syringe-dispenser with a connecting tube.

Distilled water, crystalline potassium permanganate, reducing agent solution, solution for binding nitrites, molybdate solution, aqueous sulfuric acid solution (10%), aqueous sulfuric acid solution (1: 3), ammonium persulfate in capsules of 0.5 g.

Control scale of color samples for orthophosphate concentrations (0; 0.2; 1.0; 3.5; 7.0 mg / l) from the test kit or prepared independently.

For the preparation of solutions, see Appendix 3.

Performing analysis

A. Determination of orthophosphates in drinking and natural water

1. Take 20 ml of filtered or settled analyzed water (sample) into a measuring bottle, after rinsing it 2-3 times with the same water.

Note. If the expected concentration of orthophosphates is more than 5 mg / l, it is recommended to take 5 ml of the sample (with a bottle) or 1 ml (with a syringe-dispenser), bringing the volume of the solution in the bottle to 20 ml with clean water that does not contain orthophosphates.

2. Add 10 drops of nitrite fixing solution to the sample with a dropper pipette and then 1 ml of molybdate solution with a syringe dispenser. Cap the bottle and shake to mix the solution.

The molybdate solution contains sulfuric acid. Be careful when performing this operation!

3. Leave the sample for 5 minutes. for the complete course of the reaction.

4. Add 2-3 drops of reducing agent solution to the sample with a dropper pipette. Cap the bottle and shake to mix the solution. In the presence of orthophosphates in the water, the solution becomes blue.

The reducing agent solution contains hydrochloric acid. Observe Take care when performing this operation!

5. Leave the sample for 5 minutes. for the complete course of the reaction.

6. Perform visual colorimetry on the sample. To do this, place the measuring bottle on the white field of the control scale and, illuminating the bottle with diffused white light of sufficient intensity, determine the closest color field of the control scale and the corresponding value of the concentration of orthophosphates in mg / l.

When obtaining the analysis result, take into account the dilution of the sample with pure water by entering a correction factor (for example, when diluting the sample by 4 times, i.e. when taking 5 ml of analyzed water, multiply the concentration value obtained on the scale by 4).

B. Additional operations in the determination of orthophosphates in contaminated surface and waste waters

When analyzing wastewater, operations are performed to eliminate the interfering effect of silicates, iron (III) compounds, sulfides and hydrogen sulfide, as well as tannin.

To do this, follow these steps:

1. Determine the pH of the analyzed water with a universal indicator paper. In the presence of strongly alkaline environment the sample must be neutralized with a sulfuric acid solution to pH 4-8.

2. If the analyzed water is expected to contain forcefully katov (more than 50 mg / l) and compounds iron ( III ) (more than 1 mg / L), dilute the sample before analysis, or take 5 ml of water and bring the volume of the sample to 20 ml with clean water.

3. If the analyzed water is expected to contain sulfides and hydrogen sulfide (more than 3 mg / L), prepare a dilute (slightly pink) potassium permanganate solution and add a few drops to the sample. In this case, the sample should acquire a faint pink color (with a significant color of the solution, the sample can be diluted with the analyzed water).

4. If the analyzed water is expected to contain chromates (more than 3 mg / L), change the order of addition of the solutions: first add the reducing agent solution to the sample, and then the nitrite binding solution and the molybdate solution.

5. If the analyzed water is expected to contain that Nina, it can be removed by filtration through an activated carbon column.

C. Determination of hydrolysable polyphosphates and phosphoric acid esters

1. A 50 ml sample of analyzed water (can be taken using a volumetric flask or cylinder) is placed in a conical flask.

2. Add 1 ml sulfuric acid solution (10%) and a few boiling water to the sample with a dosing syringe.

3. Attach a reflux condenser to the flask. Place the flask on a hot plate and boil the mixture at a minimum heating power for 30 minutes.

4. After cooling, transfer the mixture quantitatively to a volumetric flask. During boiling, a loss of solvent - water occurs (about
5-10 ml). Replenish the loss of water by adding distilled water to the volumetric flask up to the mark (50 ml), with which previously rinse the conical flask.

5. Take a sample (20 ml) from the resulting solution into a measuring bottle and analyze it for the content of orthophosphates. The result will represent the sum of the concentrations of orthophosphates and polyphosphates (C c) in terms of the orthophosphate anion (PO 4 3-).

6. In a separate sample of the analyzed water, without subjecting it to acid hydrolysis, determine the concentration of C 0ph orthophosphates, as described above.

7. Calculate the concentration of hydrolyzed phosphates (C pf) in mg / l according to the formula: C pf = C s - C of,

where: С с - the total concentration of polyphosphates, hydrolyzed organic phosphates and orthophosphates, determined under the conditions of hydrolysis, mg / l;

С о - concentration of orthophosphates, mg / l.

D... Mineralization and determination of total phosphorus

1. Place 50 ml of the analyzed water (or a smaller volume, diluted to 50 ml) into a porcelain dish.

2. Pour the contents of one capsule (0.5 g) of ammonium persulfate into a cup and add 1 ml of sulfuric acid solution (1: 3) there. 3. Evaporate the mixture to dryness by placing a cup on the hot plate heating element. 4. Place the cup in an oven and let it sit there for 6 hours. at a temperature of 160 ° C, then let the cup cool down to room temperature (about 0.5 hour). 5. After cooling, carefully add 30 ml of distilled water to the dry residue in the cup, stirring the mixture until the salts dissolve. Notes. 1. If the solution turns out to be colored, repeat the mineralization or take a smaller volume of the analyzed water. 2. The appearance of white turbidity due to the precipitation of calcium salts in the future does not interfere with the determination.

Analysis accuracy control

Accuracy control in the analysis for phosphate and total phosphorus content can be performed by testing a specially prepared solution of orthophosphate at concentrations equal to the values ​​given for the samples on the control scale. For this purpose, it is recommended to use monosubstituted potassium phosphate KN 2 PO 4, processed in accordance with GOST 4212. Control solutions are prepared by the gravimetric method under laboratory conditions.

Sulfur compounds.

Sulfates. Sulfates are present in almost all surface waters and are among the most important anions. The main source of sulfates in surface waters is the processes of chemical weathering and dissolution of sulfur-containing minerals, mainly gypsum, as well as the oxidation of sulfides and sulfur:

2FeS 2 + 7O 2 + 2H 2 O = 2FeSO 4 + 2H 2 SO 4;

2S + 3O 2 + 2H 2 O = 2H 2 SO 4.

Significant amounts of sulfates enter water bodies in the process of dying off organisms, oxidation of terrestrial and aquatic substances of plant and animal origin, and with groundwater runoff. Sulfates are found in large quantities in mine waters and industrial effluents from industries that use sulfuric acid, such as pyrite oxidation. Sulphates are also carried out with waste water from municipal services and agricultural production.

The ionic form SO 4 2- is characteristic only for low-mineralized waters. With an increase in mineralization, sulfate ions tend to form stable associated neutral pairs such as CaSO 4, MgSO 4.

Sulfates are actively involved in the complex sulfur cycle. In the absence of oxygen, under the action of sulfate-reducing bacteria, they are reduced to hydrogen sulfide and sulfides, which, when oxygen appears in natural water, are again oxidized to sulfates. Plants and other autotrophic organisms extract sulfates dissolved in water to build protein matter. After the death of living cells, heterotrophic bacteria release protein sulfur in the form of hydrogen sulfide, which is easily oxidized to sulfates in the presence of oxygen.

The concentration of sulfates in surface waters is subject to significant seasonal fluctuations and usually correlates with changes in the total salinity of the water. The most important determinant of the sulfate regime is the changing ratio between surface and groundwater flows. Redox processes, the biological environment in a water body and human economic activity have a noticeable effect.

MPC of sulfates in water of reservoirs for household and drinking purposes is 500 mg / dm 3, the limiting hazard indicator is organoleptic.

It is not noticed that sulfate in drinking water affects corrosion processes, but when using lead pipes, the concentration of sulfates above 200 mg / dm 3 can lead to leaching of lead into the water.

Sulfates are common components of natural waters. Their presence in water is due to the dissolution of some minerals - natural sulfates (gypsum), as well as the transport of sulfates contained in the air with rain. The latter are formed during oxidation reactions in the atmosphere of sulfur (IV) oxide to sulfur (VI) oxide, the formation of sulfuric acid and its neutralization (complete or partial):

2SO 2 + O 2 = 2SO 3,

SO 3 + H 2 O = H 2 SO 4.

The presence of sulfates in industrial wastewater is usually due to technological processes using sulfuric acid (production of mineral fertilizers, production of chemicals). Sulfates in drinking water do not have a toxic effect on humans, but they worsen the taste of water: the taste of sulfates occurs at a concentration of 250-400 mg / l. Sulfates can cause sedimentation in pipelines when two waters with a different mineral composition are mixed, for example, sulphate and calcium, CaSO 4 precipitates.

The method for determining the mass concentration of sulfate anion is based on the reaction of sulfate anions with barium cations with the formation of an insoluble suspension of barium sulfate according to the reaction:

Ba 2 + SO 4 2- = BaSO 4.

The concentration of sulfate anions is judged by the amount of barium sulfate suspension, which is determined turbidimetrickim method. The proposed, the simplest version of the turbidimetric method is based on measuring the height of the suspension column by its transparency and is applicable when the concentration of sulfate anions is not less than 30 mg / l.

The analysis is carried out in clear water (if necessary, the water is filtered). To work, you need a turbidity meter - a simple device that can be made independently (see Fig.).

Equipment and reagents

A turbidity meter, a 2 ml or 5 ml pipette with a rubber bulb (medical syringe) and a connecting tube, a dropper pipette, turbid tubes with a dot pattern at the bottom and a rubber retainer ring, a stopper for a turbid tube.

Barium nitrate solution (saturated), hydrochloric acid solution (20%).

For the preparation of solutions, see Appendix 3.

Preparation for analysis

The turbidity meter screen is installed at an angle of about 45 ° to the stand. The work is carried out under diffused, but strong enough (200-500 Lx) daytime (artificial, combined) illumination of the turbidity meter screen.

In each hole of the turbidity meter, insert a turbid test tube with a rubber ring put on it in a position that fixes the test tube so that its lower part is pushed into the cutout of the turbidity meter at a distance of about 1 cm (while the bottom of the test tube will be at the required distance - about 2 cm from the screen ).

Performing analysis

1. Place two test tubes with a picture on the bottom in the holes of the turbidity meter. Pour the analyzed water into one of the test tubes to a height
100 mm (20-30 ml).

2. Add 2 drops of hydrochloric acid solution and 14–15 drops of barium nitrate solution to the contents of the test tube. Be careful: barium nitrate is toxic!

3. Seal the tube tightly with a stopper and shake to mix the contents.

4. Leave the test tube with the solution for 5–7 minutes. to form a white precipitate (suspension).

5. Shake the closed tube again to mix the contents.

6. Pipette the resulting suspension into the second (empty) tube until the first tube shows the image on the bottom. Measure the height of the suspension column in the first tube (H p mm). Observe by directing light onto the rotating screen of the turbidity meter set at an angle of 45 °.

7. Continue transferring the suspension until the picture of the picture is hidden in it. Measure the height of the suspension column in the second tube.

8. Calculate the arithmetic mean of measurements of the height of the suspension column (h) by the formula:

9. According to the table 13 determine the concentration of sulfate anion in mg / l.

Table 13

Determination of sulfate anion concentration

		Suspension column height (h), mm	Mass concentration of sulfate anion, mg / l

Chlorine... Chlorine is widespread in nature - 0.017% (by weight) in the earth's crust. Its most widespread minerals are halite NaCl (table salt, rock salt), sylvite KCl, carnallite KCl ∙ MgCl 2 ∙ 6H 2 O, etc. The world reserves of rock salt in the bowels of the Earth are 3.5 ∙ 10 15 tons. There are a lot of chlorides dissolved in the hydrosphere. Under normal conditions, chlorine gas is almost 2.5 times heavier than air (1 liter of Cl 2 weighs 3.24 g). Chlorine dissolves in water to form yellowish chlorine water. One volume of water absorbs about two volumes of chlorine at room temperature. Chlorine is very toxic, irritating mucous membranes even in very low concentrations (0.001 mg per 1 liter of air). Chlorine reacts with the vast majority of metals and non-metals, with the exception of oxygen, carbon, nitrogen and noble gases.

Chlorides. In river waters and waters of fresh lakes, the chloride content ranges from fractions of a milligram to tens, hundreds, and sometimes thousands of milligrams per liter. In sea and underground waters, the chloride content is much higher - up to supersaturated solutions and brines.

Chlorides are the predominant anion in highly mineralized waters. The concentration of chlorides in surface waters is subject to noticeable seasonal fluctuations, correlating with changes in the total salinity of the water.

The primary sources of chlorides are igneous rocks, which include chlorine-containing minerals (sodalite, chlorapatite, etc.), salt-bearing deposits, mainly halite. Significant amounts of chlorides enter the water as a result of exchange with the ocean through the atmosphere, the interaction of atmospheric precipitation with soils, especially saline soils, as well as volcanic emissions. Industrial and waste water are becoming increasingly important.

Unlike sulfate and carbonate ions, chlorides do not tend to form associated ion pairs. Of all the anions, chlorides have the highest migration ability, which is explained by their good solubility, poorly expressed ability to sorption by suspended solids and consumption by aquatic organisms. The increased content of chlorides impairs the taste of water, makes it unsuitable for drinking water supply and limits its use for many technical and economic purposes, as well as for irrigation of agricultural land. If there are sodium ions in drinking water, then the chloride concentration above 250 mg / dm 3 gives the water a salty taste, in the case of calcium and magnesium chlorides this is observed at concentrations above 1000 mg / dm 3. The concentration of chlorides and their fluctuations, including daily, can serve as one of the criteria for the pollution of a reservoir with household wastewater.

The proposed method for determining the mass concentration of chloride anion is based on titration of chloride anions with a solution of silver nitrate, resulting in a suspension of practically insoluble silver chloride. The chemical reaction equation is written as follows:

Ag + + C1 = AgCl.

Potassium chromate is used as an indicator, which reacts with an excess of silver nitrate to form a clearly visible orange-brown precipitate of silver chromate according to the equation:

Ag + + CrO 4 = Ag 2 CrO 4,

Orange-brown

This method is called the method argentometrytitration. Titration can be performed for waters with a pH of 5.0-8.0.

The mass concentration of the chloride anion (C chl) in mg / l is calculated by the equation:

where V chl is the volume of silver nitrate solution consumed for titration, ml;

H is the concentration of the titrated solution of silver nitrate, taking into account the correction factor, g-eq / l;

V A - volume of water taken for analysis, ml;

35.5 is the equivalent mass of chlorine;

1000 - conversion factor of units of measurement from g / l to mg / l.

Equipment and reagents

2 ml or 5 ml pipette with rubber bulb (medical syringe) and connecting tube; dropper pipette, bottle labeled "10 ml" with a stopper.

Silver nitrate solution (0.05 g-eq / l) titrated, potassium chromate solution (10%).

For the preparation of solutions, see Appendix 3.

Performing analysis

1. Pour 10 ml of the analyzed water into a bottle.

2. Add 3 drops of potassium chromate solution to the bottle with a dropper pipette.

3. Cap the bottle hermetically and shake to mix the contents.

4. Gradually titrate the contents of the bottle with the silver nitrate solution with stirring until a persistent brown color appears. Determine the volume of the solution used for titration (V chl, ml).

5. Calculate the mass concentration of chloride anion (C chl, mg / l) according to the formula: C chl = V chl 178. Round the result to whole numbers.

Active chlorine. Chlorine, present in water in the form of hypochlorous acid or hypochlorite ion, is commonly called free chlorine... Chlorine, existing in the form of chloramines (mono- and di-), as well as in the form of nitrogen trichloride, is called associated chlorine. Total chlorine Is the sum of free and combined chlorine.

Chlorine can be present in other forms, including hypochlorite ion (OCl -) and chloramines, depending on conditions such as pH, temperature, organic impurities and ammonia nitrogen.

Active chlorine should be absent in the water of reservoirs, the limiting hazard indicator is general sanitary .

Chlorine can be found in water not only in the composition of chlorides, but also in the composition of other compounds with strong oxidizing properties. Such chlorine compounds include free chlorine (C1 2), hypochlorite anion (ClO -), hypochlorous acid (HCO), chloramines (substances that, when dissolved in water, form monochloramine NH 2 C1, dichloramine NHC1 2, trichloramine NCl 3). The total content of these compounds is called the term "Active chlorine". Substances containing active chlorine are divided into two groups: strong oxidants - chlorine, hypochlorites and hypochlorous acid - contain the so-called "free active chlorine", and relatively less weak oxidants - chloramines - "bound active chlorine". Due to their strong oxidizing properties, compounds with active chlorine are used for disinfection (disinfection) of drinking water and pool water, as well as for chemical treatment of some wastewater. In addition, some compounds containing active chlorine (for example, bleach) are widely used to eliminate foci of the spread of infectious contamination. Free chlorine is the most widely used disinfectant for drinking water.

In natural water, the content of active chlorine is not allowed; in drinking water, its content is set in terms of chlorine at the level of 0.3-0.5 mg / l in free form and at the level of 0.8-1.2 mg / l in bound form. Active chlorine in the indicated concentrations is present in drinking water for a short time (no more than several tens of minutes) and is completely removed even with short-term boiling of water. For this reason analysisthe selected sample for the content of active chlorine should be testeddrive immediately.

Interest in the control of chlorine content in water, especially in drinking water, increased after the realization that chlorination of water leads to the formation of noticeable amounts of chlorine hydrocarbons, harmful to public health. Chlorination of drinking water contaminated with phenol is especially dangerous. The MPC for phenols in drinking water in the absence of chlorination of drinking water is set to 0.1 mg / l, and under chlorination conditions (in this case, much more toxic and having a sharp characteristic odor of chlorophenols) - 0.001 mg / l. Similar chemical reactions can occur with the participation of organic compounds of natural or technogenic origin, leading to various toxic organochlorine compounds - xenobiotics.

The proposed iodometric method is based on the property of all compounds containing active chlorine in an acidic medium to release free iodine from potassium iodide:

Free iodine is titrated with sodium thiosulfate in the presence of starch as described in the determination of dissolved oxygen. The reaction is carried out in a buffer solution at pH 4.5, and then nitrites, ozone and other compounds do not interfere with the determination. However, substances that interfere with the determination are other strong oxidants that also release iodine from potassium iodide - chromates, chlorates, etc. Concentrations in which these oxidants interfere may be present in wastewater, but are unlikely in drinking and natural water. The method can also be used to analyze turbid and colored waters.

The concentration of active chlorine (C AX) in mg / l is calculated from the results of titration, for which a sodium thiosulfate solution with a concentration of 0.005 g-eq / l is usually used. The calculation is carried out according to the formula:

where V T is the amount of sodium thiosulfate solution with a concentration of 0.005 g-eq / l, consumed for titration, ml; K is a correction factor that takes into account the deviation of the exact actual concentration of thiosulfate from the value of 0.005 g-eq / l (for most cases, the value of K is taken equal to 1); 0.177 - active chlorine content in mg, corresponding to 1 ml of thiosulfate solution with concentration
0.005 g-eq / l; V A - volume of water sample taken for analysis, ml; 1000 - conversion factor of units of measurement from milliliters to liters.

The sensitivity of the method is 0.3 mg / L with a sample volume of 250 ml, however, when using thiosulfate solutions with different concentrations, the sample volume can be, depending on the required detection sensitivity, from 500 to 50 ml of water or less. The limiting hazard indicator for active chlorine is general sanitary.

Equipment and reagents

A conical flask for 250-500 ml with volumetric graduations (if the flask is not graduated, then a graduated cylinder is also required), a burette or pipette graduated for 2-5 ml with a syringe and a connecting tube, a syringe-dispenser (pipette) for 1 ml (2 pcs.), scissors.

Potassium iodide in capsules of 0.5 g, buffer acetate solution (pH 4.5), titrated sodium thiosulfate solution (0.005 g-eq / l), starch solution (0.5%).

For the preparation of solutions, see Appendix 3.

1. Pour the analyzed water into the conical flask up to the mark (for example, 50 ml) or using a graduated cylinder. Rinse the flask with the analyzed water.

2. Place 1.0 ml of acetate buffer solution into the flask using a syringe or pipette, mix the contents of the flask.

3. Add the contents of one capsule (about 0.5 g) of potassium iodide to the conical flask. Stir the contents of the flask until the salt dissolves.

4. Titrate the evolved iodine with thiosulfate solution. To do this, take 2-5 ml of thiosulfate solution into a burette (pipette) fixed in a stand and connected through a tube with a syringe and titrate the sample to a slightly yellow color.

5. Add others syringe-dispenser (pipette) 1 ml of starch solution (the solution in the flask turns blue) and continue titration until the solution is completely discolored.

Note. After the color change, the sample must be kept for another 0.5 min. for the complete course of the reaction. If the color is restored, some more titrant solution must be added.

6. Determine the total volume of the thiosulfate solution used for the titration (both before and after the addition of the starch solution).

7. Calculate the concentration of the total residual active chlorine (С АХ) in mg / l according to the formula given above.

If necessary, repeat the analysis by decreasing (increasing) the sample volume.

As an express portable field modification method with a sensitivity of at least 0.3-0.5 mg / l for the determination of active chlorine in drinking, tap and natural water, it can be recommended to use a thiosulfate solution with a concentration of 0.0025 g-eq / l, when taking a sample of 50 ml and titration with using a calibrated dropper pipette. In this case, the concentration of active chlorine (С АХ) in mg / l is calculated by the formula:

where: N is the number of drops of sodium thiosulfate solution consumed for titration;

0.1 - the amount of residual active chlorine in mg, corresponding to the content in 1 drop of sodium thiosulfate solution with a concentration of 0.0025 g-eq / l, taking into account the titration of a 50 ml water sample;

K is the correction factor for a given dropper pipette, established experimentally and taking into account the difference in droplet volumes, detached from different pipettes (usually the K value is close to 1).

Calculation example . When analyzing tap water as a result of titration of a 50 ml sample with a thiosulfate solution with a concentration of 0.0025 g-eq / l using a calibrated dropper pipette (K = 0.92), 11 drops of a thiosulfate solution were consumed for titration. Therefore, the content of active chlorine in water is:

Sodium... Sodium is one of the main components of the chemical composition of natural waters, which determines their type. The main source of sodium in the surface waters of the land are igneous and sedimentary rocks and native soluble chloride, sulfate and carbonate sodium salts. Biological processes in the catchment area, which result in the formation of soluble sodium compounds, are also of great importance. In addition, sodium enters natural waters with domestic and industrial wastewater and with water discharged from irrigated fields.

The mass concentration of sodium cation (SNA) in mg / l is determined by the calculation method, making the calculation by the formula:

C HA = (A-C OZH) 23,

where: A - the sum of the mass concentrations of the main anions (determined using the data in Table 14), mg-eq / l;

C coolant - the value of the total hardness, mg-eq / l;

23 is the equivalent mass of sodium.

Potassium... Potassium is one of the main components of the chemical composition of natural waters. Its source in surface waters is geological rocks (feldspar, mica) and soluble salts. Various soluble potassium compounds are also formed as a result of biological processes occurring in the weathering crust and soils. Potassium is characterized by a tendency to be sorbed on highly dispersed particles of soils, rocks, bottom sediments and to be retained by plants in the process of their nutrition and growth. This leads to a lower mobility of potassium compared to sodium, and therefore potassium is found in natural waters, especially surface waters, in a lower concentration than sodium.

Potassium also enters natural waters with domestic and industrial wastewater, as well as with water discharged from irrigated fields, and with surface water runoff from agricultural land.

Concentration in river water usually does not exceed 18 mg / dm 3, in groundwater it ranges from milligrams to grams and tens of grams per 1 dm 3, which is determined by the composition of the water-bearing rocks, the depth of groundwater and other conditions of the hydrogeological situation.

MPC bp potassium is 50 mg / dm 3.

Fluorine (fluorides). Fluorine enters river waters from rocks and soils during the destruction of fluorine-containing minerals (apatite, tourmaline) with soil water and during direct flushing by surface waters. Precipitation is also a source of fluorine. An increased content of fluorine can be in some wastewater from glass and chemical industries (production of phosphorus fertilizers, steel, aluminum), in some types of mine water and in wastewater from ore processing factories.

In natural waters, fluorine is in the form of fluoride ion F - and complex ions 3-, -, 2-, 3-, 3-, 2-, etc.

The migration ability of fluorine in natural waters largely depends on the content of calcium ions in them, giving a poorly soluble compound with fluorine ions (the product of the solubility of calcium fluoride L = 4 · 10 -11). An important role is played by the mode of carbon dioxide, which dissolves calcium carbonate, converting it into bicarbonate. Increased pH values ​​increase the mobility of fluorine.

Fluorine is a stable component of natural waters. Intra-annual fluctuations in fluorine concentration in river waters are small (usually no more than 2 times). Fluorine enters rivers mainly with groundwater. The fluorine content in the flood period is always lower than in the low-water period, since the share of groundwater supply decreases.

Increased amounts of fluorine in water (more than 1.5 mg / dm 3) have a harmful effect on humans and animals, causing bone disease (fluorosis). In addition, excess fluoride in the body precipitates calcium, which leads to disturbances in calcium and phosphorus metabolism. However, the very low fluoride content in drinking water (less than 0.01 mg / dm 3) is also harmful to health, causing the risk of dental caries. For these reasons, the determination of the concentration of fluorine in drinking water, as well as groundwater (for example, water from wells and artesian wells) and water of reservoirs for household and drinking purposes is very important.

The proposed method for determining fluorine in water is based on the reaction of fluorides with lanthanalizarin complexone. This forms a blue-colored ternary complex compound of fluoride, trivalent lanthanum and alizarin complexone.

Compounds of aluminum, iron and an increased content of organic substances interfere with the determination. Aluminum binds fluoride ions to form complexes A1F 2+ and A1F 2 +. Due to the fact that the aluminum content in drinking and natural waters, which usually have a pH of 6-8, is usually very low, the effect of aluminum is neglected.

The determination of fluorine in this modification of the method is significantly influenced by iron compounds at a concentration of more than 2 mg / l. Therefore, in highly ferrous waters, fluorine is not determined by this method (for this purpose, a potentiometric
method).

With an increased content of dissolved organic substances in the analyzed water, the colorimetrized liquid acquires a different (masking) color, which differs in color from the color caused only by fluorides. To eliminate this phenomenon, the sample must first be cleaned of organic matter - shake the water with a small amount of powdered activated carbon, then filter it from the coal and only then analyze it for fluorine content.

Equipment and reagents

Colorimetric test tube labeled "5 ml", scissors.

Buffer mixture amber-boric in capsules of 0.1 g, lanthanalizarin complexon varnish.

Control scale of color samples for the determination of fluoride ion (0; 0.5-1.2; 1.5-2.0 mg / l) from the test kit or prepared independently.

For the preparation of solutions, see Appendix 3.

Executing a definition

1. Pour the analyzed water into the colorimetric tube up to the mark (5 ml).

2. Add the contents of one capsule (about 0.1 g) of the buffer mixture. Mix the tube by shaking until the mixture dissolves (to pH 5).

3. Using a syringe with a pipette tip, add 2.0 ml of lanthanalizarin complexone varnish, then mix the mixture again.

4. Leave the mixture for 20 minutes. to complete the reaction.

5. Compare the color of the solution in the bottle against the white background with the control scale of the color samples.

If the color of the sample is more intense than the sample
"2.0 mg / l", dilute the analyzed water 2-5 times with distilled water and repeat the determination. When calculating the result, take into account the dilution of the sample.

Analysis accuracy control

The control of the accuracy of the analysis in the determination of fluorides is carried out using control solutions with a known content of the fluoride anion (see Appendix 1) or using a verified (exemplary) ion-selective electrode by the potentiometric method.

Total salt content. To calculate the total salt content by the sum of the concentrations of the main anions in milligram-equivalent form their mass concentrations, determined during the analysis and expressed in mg / l, multiply by the coefficients indicated in table. 14, then add up (GOST 1030).

Table 14

Concentration conversion factors from mg / l to mg-eq / l

The concentration of the potassium cation in this calculation (for natural waters) is conventionally taken into account as the concentration of the sodium cation. Round off the obtained result to whole numbers (mg-eq / l).

Previous

How to test (analyze) mineral water for quality at home? Varieties of mineral waters, their characteristics and requirements for them. Regulatory documents for mineral waters. What is considered to be the quality standards of mineral water. How is the analysis of mineral water carried out in laboratory conditions, methods of analysis. Before you test (analyze) mineral water for quality, you need to understand the varieties of this liquid and the requirements for its quality. Only then can you judge the quality of the liquid in the bottle based on the test results.

Varieties of mineral water

Mineral water is of natural origin and artificial. The first is made from liquid collected from deep-water artesian wells. Only registered sources may be used for the production of such water. Usually, the quality of such a liquid can be judged by the set and safety of the mineral components. There are several types of mineral water:

• Water for the treatment of people. It can only be taken on the recommendation of a doctor. The degree of mineralization of such a liquid is 8 g / l.
• Medical canteen. The concentration of useful mineral compounds in this type of liquid should be in the range of 2-8 g / l.
• Table water. This kind can be drunk regularly. Its mineralization level should be 1-2 g / l.
• Table water with a minimum degree of mineral saturation. Their volume usually does not exceed 1 g / l.

The main difference between artificial water is that it is produced at a factory, but in terms of the composition and quantity of mineral compounds, such water does not differ from natural water. At the same time, the label must indicate that the water is produced artificially.

Also, mineral water can be carbonated and non-carbonated. In this case, carbonation can occur naturally or artificially. Also, according to the presence of cations and anions in water, it can be divided into 31 types, including chloride, sulfate, hydrocarbonate and mixed waters.

Mineral water quality standards

The quality of mineral waters, be it table or medicinal water, is regulated by GOST R 54316-2011. The quality standards for such water are:

1. Production method. Natural mineral water is extracted from the well. The produced water is purified and filtered. There are also separate standards for the cleaning and filtration process. By standards, the liquid should be crystal clear, but a slight sediment of mineral compounds is allowed. The taste and smell must match the composition of the liquid.
2. The standards impose a restriction on a certain list of chemical elements. So, in water with minerals, the content of ammonium in an amount not exceeding 2 mg / l, phenolic substances in a volume of 0.001 mg / l, nitrates up to 50 mg / l, lead up to 0.3 mg / l, nitrites up to 2 mg / l is allowed. The concentration of arsenic is also stipulated: for medicinal water, this indicator cannot exceed 3 mg / l, and in table medicinal water, not higher than 1.5 mg / l.
3. The concentration of nitrogen dioxide (carbonation of the beverage) cannot be less than 0.3%. The production of still water is also allowed.
4. Spill requirements. The water is sold in tightly sealed bottles.

After that, the product must be tested to confirm its quality. For this, a sample is analyzed, in which its organoleptic qualities, composition, microbiological indicators are checked, and radiological control is carried out. Also, the safety of all components of the mineral water is strictly controlled, the physical usefulness of the elements is checked.

Analysis of mineral water at home

Each of us can check the quality of bottled water in affordable ways. To do this, you need to conduct a number of small experiments:

• For the first test, you will need to drip water from a bottle onto a clean glass or mirror and let it dry. If after that no trace remains on the surface, then the water is clean. A dried whitish spot will indicate the presence of an excess of chlorine, and circular stains at the place of the drop will indicate an excess of salts.
• The second analysis requires bottled water to be kept in a jar. To do this, pour a sample of water into a clean three-liter jar and put it in a dark place for several days. High-quality water should remain the same clean and transparent, odorless and free of sediment. If the water becomes cloudy, turns green, has a sediment or an unpleasant odor, it means that bacteria were present in it. An oil film on the surface of the water will indicate the presence of harmful chemicals.
• If mineral water without gas is poured into a dark-colored saucepan and boiled for 10-15 minutes, then after draining the liquid, conclusions can be drawn about the quality of the water. If there is a white coating, sediment or scale on the walls of the dishes, we can say that there is an excess of salts, iron oxide, calcium in the water.

Mineral water expertise

Organoleptic analysis of high-quality mineral water should give the following results: it is a colorless transparent liquid with a characteristic taste and smell of dissolved minerals. When storing such a liquid, a slight precipitate is allowed.

Mineral water test can be carried out:

• Express method
• By weight method

The first method is carried out as follows. First, 100 ml of water from a bottle is drawn into a clean glass. She is allowed to stand for 10 minutes. Then investigate the trace of a drop of this liquid on the glass. Plain drinking water can form a salt circuit. Mineral water will have a vague track outline. In this case, its inner part will be filled with a whitish coating. The trail of a drop in medicinal table waters should be more densely filled with a white bloom, while in medicinal waters the trail will be completely white.

The weighing method allows in laboratory conditions to determine the concentration of mineral salts in grams per cubic decimeter.

If you want to check the quality of mineral water, then you can order the most reliable analysis only in the laboratory. No amount of home checks will give you the full picture. To carry out an analysis in our laboratory, you need to contact us at the numbers indicated on the website.