GOST for determining the specific electrical conductivity of water. Water: electrical conductivity and thermal conductivity
Electrical conductivity is a numerical expression of the ability of an aqueous solution to conduct electric current. The electrical conductivity of natural water depends mainly on the concentration of dissolved mineral salts and temperature. Natural waters are mainly solutions of mixtures of strong electrolytes. The mineral part of the water consists of Na+, K+, Ca2+, Cl-, SO42-, HCO3- ions. These ions determine the electrical conductivity of natural waters. The presence of other ions, for example, Fe3+, Fe2+, Mn2+, Al3+, NO3-, HPO4-, H2PO4- does not greatly affect the electrical conductivity if these ions are not contained in significant quantities in the water. The reliability of assessing the content of mineral salts based on specific electrical conductivity is largely influenced by temperature and the unequal electrical conductivity of various salts.The normalized mineralization values approximately correspond to a specific electrical conductivity of 2 mS/cm (1000 mg/dm3) and 3 mS/cm (1500 mg/dm3) in the case of both chloride (in terms of NaCl) and carbonate (in terms of CaCO3) mineralization.
"The value of S is measured in Siemens (Sm), milliSiemens (mSm) or microSiemens (µS), and λ - in µS/cm (microSiemens per centimeter). For a rough estimate of mineralization, you can adhere to this empirically found relationship:
Salt content (mg/l) = 0.65 µS/cm
That is, to determine the salt content, the measured conductivity value is multiplied by a factor of 0.65. In fact, the value of this coefficient varies depending on the type of water in the range of 0.55-0.75.
Sodium chloride solutions conduct current better:
NaCl content (mg/l) = 0.53 µS/cm
or 1 mg/l NaCl provides an electrical conductivity of 1.9 µS/cm. "
SPECIFIC CONDUCTIVITY OF WATER
– an instrumentally determined indirect characteristic of fresh water mineralization (salinity of sea water) (see electrical conductivity of water). U.e.v. measured using platinum or steel electrodes immersed in water, through which an alternating current with a frequency of 50 Hz (in low-mineralized water) to 2000 Hz or more (in salt water) is passed, by measuring electrical resistance. To eliminate the influence of temperature, measurements are made at a constant temperature of 15°C (in oceanology), 18°C (in Russia, but in some foreign countries - at 20° or 25°C), or are reduced to it using empirical formulas. Calculation of U.e.v. is carried out according to the formula k = C(K) T / R, where C is the capacity of the device sensor, which depends on the material and size of the electrodes and has a dimension of cm–1, determined by calibrating the device using solutions of potassium chloride with a known value of e.e.v. ; K T - temperature coefficient for bringing the measured value at any temperature to its accepted constant value; R is the measured electrical resistance of water by the device, in Ohms. U.e.v. salt water is usually expressed in S/m (Si - Siemens, the reciprocal of Ohm), fresh water - in microsiemens (µS/cm). U.e.v. distilled water is 2-5 µS/cm, precipitation - from 6 to 30 µS/cm or more, in areas with heavily polluted air, river and fresh lake waters 20-800 µS/cm."
The ability of one cubic centimeter of a substance to conduct a certain electrical charge is called the specific electrical conductivity, or electrical conductivity, of that substance. Electrical conductivity is the inverse phenomenon of electrical resistance and is measured in units called mo. (This word is the reverse spelling of the unit of resistance, ohm.) Because mo is too large a unit to measure
Electrical conductivity of fresh water and groundwater; ppm mo, micromo are used for this purpose.
Rice. 3.7. Stiff diagram for depicting the composition of water in longitudinal coordinates.
Outlined areas help you quickly compare test results. Diagram a shows the results of the analysis shown in Fig. 3.4, a.
Rice. 3.8. A two-axis graph showing the total salinity and chloride content of groundwater. The results of 100 analyzes taken from various papers are presented. It can be seen that as the mineralization of most groundwater increases, the NaCl content in them increases.
Rice. 3.9. Three-line diagram proposed by Piper. The chemical characteristics of sea water (A) and drinking underground water (B) are shown in percentage equivalents. The results of each analysis are represented by three points:
two on triangular fields and one on a summing diamond field.
The specific electrical conductivity of water depends on temperature, the nature of the ions and their concentration (Fig. 3.10). Typically, the specific electrical conductivity of water is given for 25 ° C, so it depends only on the concentration and nature of the dissolved components. Since electrical conductivity is measured very quickly, it can be used to easily determine the chemical composition of water.
Among common types of natural waters for a given total salinity, waters containing calcium bicarbonate and sulfate generally have the lowest conductivity, and waters containing sodium chloride have the highest conductivity. The total salinity of fresh water in parts per million can be approximately determined by multiplying its electrical conductivity in micromo by 0.7. However, a more precise relationship is observed between the form of expression of water mineralization in equiv/million and its electrical conductivity, expressed in micromo. For almost pure water, if we divide the value of specific electrical conductivity by 100, we obtain the total mineralization of water in equivalents per 1 million with an accuracy of 5%. For water with mineralization from 1 to 10 equiv/ppm, the accuracy of the obtained value is about 15%. Logan believes that the total mineralization of water B, expressed in equivalents per 1 million, and its specific electrical conductivity C are related by the following empirical relationships:
C = 100 V, (3.2)
When in
C= 12.27 + 86.38 V + 0.835 V 2
, (3.3)
When B = 1 - 3;
C = B(95.5-5.54 lg B), (3.4)
When B = 3 - 10;
C = 90 V, (3.5)
When B > 10 with a predominance of the HCO - 3 anion;
C = 123 V, 0,939 (3.6)
When B>10 with the presence of anise Cl - ;
C = 101 V, 0,949 (3.7)
When B > 10 with a predominance of SO 2-4 anion
Rice. 3.10. Specific electrical conductivity of aqueous solutions of various compounds. The effect of temperature on the electrical conductivity of water is especially evident in the example of NaCl content.
Since the sum of anion equivalents is usually slightly different from the sum of cation equivalents, the value of B is taken as the average of these sums. The given dependences are valid only for values of B less than 1000 equiv/million.
Pure water has a specific electrical conductivity of 0.055 micromo at 25° G, laboratory distilled water - from 0.5 to 5, rain water usually - from 5 to 30, underground water suitable for drinking - from 30 to 2000, ocean water - from 45,000 up to 55,000, oil field brines - more than 100,000 micromo.
Electrical propertieswater.
water consists of three atoms,
molar mass water 18 10 -3 kg/mol,
is part of all organisms
occupies 71% of the planet's surface,
molecules water do not form a crystal lattice,
water is the most commonly used solvent.
Water is the most abundant substance on Earth. Almost 3/4 of the surface of the globe is covered with water, forming rivers and lakes, oceans, and seas. A lot of water exists in a gaseous state as vapor in the atmosphere; it lies in the form of huge masses of snow and ice all year round on the tops of high mountains and in polar countries.
In the bowels of the earth there is also water that saturates the soil and rocks.
Natural water is never completely pure. Rainwater is the purest, but it also contains small amounts of various impurities that it absorbs from the air.
The amount of impurities in fresh waters usually ranges from 0.01 to 0.1%. Sea water contains 3.5% dissolved substances, the main mass of which is sodium chloride. Water containing large amounts of calcium and magnesium salts is called hard water and, in contrast to soft water, water For example, rainwater, hard water produces little foam with soap, and forms scale on the walls of boilers after boiling.
The aquatic environment includes surface and underground water. Superficial water mainly concentrated in the ocean, containing 1 billion 375 million km 3 - about 98% of the total water on the ground. The ocean surface (water area) is 361 million square kilometers. It is approximately 2.4 times larger than the land area of the territory, occupying 149 million km 2. The water in the ocean is salty, and most of it (more than 1 billion km 3) maintains a constant salinity of about 3.5% and a temperature of approximately 3.7 °C. Noticeable differences in salinity and temperature are observed almost exclusively in the surface layer water, as well as in marginal and especially in the Mediterranean seas. The content of dissolved oxygen in water decreases significantly at a depth of 50-60 m.
We can say that all living things consist of water and organic matter. Without water a person, for example, could live no more than 2-3 days, but without nutrients he can live for several weeks. To ensure normal existence, a person must introduce into the body water approximately 2 times more by weight than nutrients. Loss by the human body is more than 10% water may lead to death. On average, the body of plants and animals contains more than 50% water, in the body of a jellyfish there are up to 96, in algae 95...99, in spores and seeds from 7 to 15 %, The soil contains at least 20% water, in the human body water makes up about 65% (in the body of a newborn up to 75, in an adult 60%). Different parts of the human body contain different amounts water: The vitreous body of the eye consists of water by 99%, in the blood it contains 83, in adipose tissue 29, in the skeleton 22 and even in tooth enamel 0.2%.
Molecule water consists of two hydrogen atoms and one oxygen atom. As part of the regular water H 2 O there is a small amount of heavy water D 2 O and a very small amount of superheavy water T 2 O. In a heavy molecule water instead of ordinary hydrogen H - protium - its heavy isotope D - deuterium is included in the composition of the superheavy molecule water includes an even heavier hydrogen isotope T - tritium. In natural water, for every 1,000 H2O molecules there are two D2O molecules and for one T2O molecule there are 1019 H2O molecules.
Heavy water D2O is colorless, odorless, tasteless, and cannot be absorbed by living organisms. Its freezing point is 3.8 °C, its boiling point is 101.42 °C and its maximum density is 11.6 °C. In terms of hygroscopicity, heavy water is close to sulfuric acid. Its density is 10% greater than natural density water, and the viscosity exceeds the natural viscosity water by 20%. The solubility of salts in heavy water is approximately 10% less than in ordinary water. Since D 2 O evaporates more slowly than light water, in tropical seas and lakes there is more of it than in reservoirs of polar latitudes.
There are six isotopes of oxygen in nature. Three of them are radioactive. The stable isotopes are O 16, O 17 and O 18. During evaporation, the O 16 isotope mainly passes into water vapor, while the unevaporated water is enriched in the O 17 and O 18 isotopes. In the waters of seas and oceans, the ratio of O 18 to O 16 is greater than in river waters. Heavy oxygen isotopes are more common in animal shells than in water. The content of the O 18 isotope in atmospheric air depends on temperature. The higher the air temperature, the more water evaporates and the more O 18 goes into the atmosphere. During the period of glaciations of the planet, the content of the O 18 isotope in the atmosphere was minimal.
In total you can get 36 varieties water. Molecules are more common in nature water, constructed from the most common isotopes. Natural water contains 99.73% of H 2 O 16 molecules, 0.2% of H 2 O 18 molecules and 0.04% of H 2 O 17 molecules.
With conventional electrolysis water, containing, along with H 2 O molecules, also a small amount of D 2 O molecules formed by the heavy isotope of hydrogen, predominantly H 2 O molecules undergo decomposition. Therefore, during long-term electrolysis water the residue is gradually enriched with D 2 O molecules. From such a residue, after repeated electrolysis in 1933, it was possible for the first time to isolate a small amount water, consisting almost 100% of D 2 0 molecules and called heavy water.
The properties of heavy water are noticeably different from ordinary water. water. Reactions with heavy water proceed more slowly than with normal water. Heavy water is used as a neutron moderator in nuclear reactors.
Knowing the physical properties water and ice, people have been using them in their practical activities for a long time. For example, sometimes laying bare electrical wires directly on ice is used, since electrical conductivity dry ice and snow are very small. It is many times less than electrical conductivity water. Various impurities have a great influence on electrical conductivity water and almost do not change the electrical conductivity of ice. Electrical conductivity chemically pure water caused by partial dissociation of the molecule water into H + and OH – ions. Main importance for electrical conductivity and water and ice have movements of H + ions (“proton hopping”). Electrical conductivity chemically pure water at 18°C is equal to 3.8 -10 –8 Ohm -1 cm –1 a electrical conductivity nautical water about 5-10 –2 Ohm -1 cm –1. Electrical conductivity fresh natural water maybe 1,000 times less than nautical. This is explained by the fact that more salts are dissolved in the water of the seas and oceans than in river water.
An essential characteristic of the electrical properties of a substance is provided by the relative dielectric constant. U water it has a value in the range of 79...81, for ice 3.26, for water vapor 1.00705.
The product of the concentrations of hydrogen and hydroxyl ions in chemically pure water is a constant value equal to 10 -14 at a temperature of 25 °C. It remains unchanged in the presence of substances that dissociate to form hydrogen and hydroxyl ions. In pure water, the concentrations of hydrogen and hydroxyl ions are 10 -7 mol/dm 3, which corresponds to the neutral state of the solution. In acidic solutions [H + ] > 10 -7 mol/dm 3, and in alkaline solutions [H + ]< 10 -7 моль/дм 3 .
For convenience, expressing the concentration of hydrogen ions in water uses a value that is the decimal logarithm of their concentration taken with the opposite sign. This quantity is called pH value and is designated pH(pH = - log¢).
The pH value is one of the most important indicators of water quality and characterizes the state of acid-base balance of water. The development and vital activity of aquatic biota, the forms of migration of various elements, and the aggressive effect of water on host rocks, metals, and concrete depend on the pH value.
The pH value of surface waters is influenced by the state of carbonate equilibrium, the intensity of the processes of photosynthesis and decay of organic substances, and the content of humic substances.
In most water bodies, the pH of the water usually ranges from 6.3 to 8.5. In river and lake waters, pH values are lower in winter compared to summer.
The pH value of surface waters subject to intense pollution by wastewater or the influence of groundwater may vary within wider limits due to the presence of strong acids or bases in their composition.
Specific electrical conductivity (electrical conductivity) - quantitative characteristic of water’s ability to conduct electric current. In a purely physical sense, this is the reciprocal of the electrical resistance of water at a temperature of 25 ° C, located between two electrodes with a surface of 1 cm 2, the distance between which is 1 cm. The unit of electrical conductivity is Siemens per 1 m (S/m). For water, derived values are used as a unit of measurement - milliSiemens per 1 m (mS/m) or microSiemens per 1 cm (μS/cm).
In most cases, the specific electrical conductivity of land surface waters is an approximate characteristic of the concentration of inorganic electrolytes in water - Na cations+ , K + , Ca 2+ , Mg 2+ and Clˉ, SO 4 2-, HCO 3 - anions . The presence of other ions, e.g. Fe (II), Fe (III), Mn(II), NO 3 - , HPO 4 2- usually has little effect on the value of electrical conductivity, since these ions are rarely found in water in significant quantities. Hydrogen and hydroxyl ions in the range of their usual concentrations in surface waters of land have practically no effect on the electrical conductivity. The influence of dissolved gases is equally small.
Thus, the specific electrical conductivity of land surface waters depends mainly on their mineralization and usually ranges from 50 to 10,000 µS/cm.
The pH of water is measured potentiometrically, and the specific electrical conductivity is measured by the conductometric method using appropriate instruments - pH meters (ionomers) and conductometers. Modern devices (ionomers-salin meters) are equipped with sensors for both indicators and allow them to be measured almost simultaneously.
RD 52.24.495-2005
GUIDANCE DOCUMENT
HYDROGEN INDICATOR AND SPECIFIC ELECTRICAL CONDUCTIVITY OF WATER. METHOD OF PERFORMING MEASUREMENTS USING THE ELECTROMETRIC METHOD
Date of introduction 2005-07-01
Application area
This guidance document establishes methods for performing measurements (hereinafter referred to as the method) of the hydrogen index in the range from 4 to 10 units. pH and electrical conductivity in the range from 5 to 10,000 µS/cm in samples of land surface waters and treated wastewater by electrometric method.
Measurement error characteristics
Measurement method
When measuring the pH of water using the electrometric method, a system is used that consists of a glass electrode, the potential of which depends on the concentration (activity) of hydrogen ions, and an auxiliary electrode. When immersed in a water sample, the electrode system develops an emf that linearly depends on the activity of hydrogen ions.
The measurement of electrical conductivity is based on measuring the electrical resistance of a solution located between two platinum (platinized) electrodes with a surface area of 1 cm 2, the distance between which is 1 cm.
When the temperature changes by 1 °C, the value of the specific electrical conductivity changes (increases with increasing temperature) by approximately 2%. Therefore, to eliminate this error, measurements are carried out in a temperature-controlled sample or using an automatic temperature compensator. Otherwise, appropriate corrections are made to the results.
Safety and environmental requirements
where v t is the value of specific electrical conductivity at measurement temperature, µS/cm;
f - temperature correction (Appendix).
If the device is calibrated in other units, the measurement result must be converted to microsiemens per centimeter.
where pH is the arithmetic mean of two results, the difference between which does not exceed the repeatability limit r (0.06 pH units).
where: v is the arithmetic mean of two results, the difference between which does not exceed the repeatability limit r (2.77 s r);
± D - limits of measurement error ( table ).
In this case, the actual measurement temperature is indicated if automatic or mathematical correction of the result was carried out. The numerical values of the measurement result must end with a digit of the same digit as the values of the error characteristic.
12 Quality control of measurement results when implementing the technique in the laboratory
3 When implementing the technique in the laboratory, the following is provided:
Operational control by the performer of the measurement procedure (based on an assessment of repeatability when implementing a separate control procedure);
Monitoring the stability of measurement results (based on monitoring the stability of the standard deviation of repeatability).
The algorithm for operational control by the performer of the measurement procedure is given in RD 52.24.495-2005.
The frequency of operational monitoring and procedures for monitoring the stability of measurement results are regulated in the Laboratory Quality Manual.
Chief metrologist of the State Chemical Institute A.A. Nazarova
Drinking water quality standards SanPiN 2.1.4.1074-01. Drinking water. (WHO, EU, USEPA). drinking water, packaged in containers (according to SanPiN 2.1.4.1116 - 02), indicators of vodka (according to PTR 10-12292-99 with amendments 1,2,3), water for the production of beer and non-alcoholic products , network and make-up water for hot water boilers (according to RD 24.031.120-91), feed water for boilers (according to GOST 20995-75), distilled water (according to GOST 6709-96), water for electronic equipment (according to OST 11.029.003- 80, ASTM D-5127-90), for electroplating industries (according to GOST 9.314-90), for hemodialysis (according to GOST 52556-2006), purified water (according to FS 42-2619-97 and EP IV 2002), water for injections (according to FS 42-2620-97 and EP IV 2002), water for irrigation of greenhouse crops.
This section provides the main indicators of water quality standards for various industries.
Quite reliable data from an excellent and respected company in the field of water purification and water treatment "Altir" from Vladimir
| Indicators | SanPiN2.1.4.1074-01 | WHO | USEPA | EU | |||
|---|---|---|---|---|---|---|---|
| Unit measurements | MPC standards, no more | Harmfulness indicator | Hazard Class | ||||
| pH value | units pH | within 6-9 | - | - | - | 6,5-8,5 | 6,5-8,5 |
| Total mineralization (dry residue) | mg/l | 1000 (1500) | - | - | 1000 | 500 | 1500 |
| General hardness | mEq/l | 7,0 (10) | - | - | - | - | 1,2 |
| Oxidability permanganate | mg O2/l | 5,0 | - | - | - | - | 5,0 |
| Petroleum products, total | mg/l | 0,1 | - | - | - | - | - |
| Surfactants (surfactants), anionic | mg/l | 0,5 | - | - | - | - | - |
| Phenolic index | mg/l | 0,25 | - | - | - | - | - |
| Alkalinity | mg HCO3-/l | 0,25 | - | - | - | - | 30 |
| Inorganic substances | |||||||
| Aluminum (Al 3+) | mg/l | 0,5 | social-t. | 2 | 0,2 | 0,2 | 0,2 |
| Ammonia nitrogen | mg/l | 2,0 | social-t. | 3 | 1,5 | - | 0,5 |
| Asbestos | mill.hair/l | - | - | - | - | 7,0 | - |
| Barium (Ba 2+) | mg/l | 0,1 | social-t. | 2 | 0,7 | 2,0 | 0,1 |
| Beryllium(Be 2+) | mg/l | 0,0002 | social-t. | 1 | - | 0,004 | - |
| Boron (B, total) | mg/l | 0,5 | social-t. | 2 | 0,3 | - | 1,0 |
| Vanadium (V) | mg/l | 0,1 | social-t. | 3 | 0,1 | - | - |
| Bismuth (Bi) | mg/l | 0,1 | social-t. | 2 | 0,1 | - | - |
| Iron (Fe,total) | mg/l | 0,3 (1,0) | org. | 3 | 0,3 | 0,3 | 0,2 |
| Cadmium (Cd,total) | mg/l | 0,001 | social-t. | 2 | 0,003 | 0,005 | 0,005 |
| Potassium (K+) | mg/l | - | - | - | - | - | 12,0 |
| Calcium (Ca 2+) | mg/l | - | - | - | - | - | 100,0 |
| Cobalt (Co) | mg/l | 0,1 | social-t. | 2 | - | - | - |
| Silicon (Si) | mg/l | 10,0 | social-t. | 2 | - | - | - |
| Magnesium (Mg 2+) | mg/l | - | social-t. | - | - | - | 50,0 |
| Manganese (Mn,total) | mg/l | 0,1 (0,5) | org. | 3 | 0,5 (0,1) | 0,05 | 0,05 |
| Copper (Cu, total) | mg/l | 1,0 | org. | 3 | 2,0 (1,0) | 1,0-1,3 | 2,0 |
| Molybdenum (Mo,total) | mg/l | 0,25 | social-t. | 2 | 0,07 | - | - |
| Arsenic (As,total) | mg/l | 0,05 | social-t. | 2 | 0,01 | 0,05 | 0,01 |
| Nickel (Ni,total) | mg/l | 0,01 | social-t. | 3 | - | - | - |
| Nitrates (by NO 3-) | mg/l | 45 | social-t. | 3 | 50,0 | 44,0 | 50,0 |
| Nitrites (by NO 2-) | mg/l | 3,0 | - | 2 | 3,0 | 3,5 | 0,5 |
| Mercury (Hg, total) | mg/l | 0,0005 | social-t. | 1 | 0,001 | 0,002 | 0,001 |
| Lead (Pb,total) | mg/l | 0,03 | social-t. | 2 | 0,01 | 0,015 | 0,01 |
| Selenium (Se, total) | mg/l | 0,01 | social-t. | 2 | 0,01 | 0,05 | 0,01 |
| Silver (Ag+) | mg/l | 0,05 | - | 2 | - | 0,1 | 0,01 |
| Hydrogen sulfide (H 2 S) | mg/l | 0,03 | org. | 4 | 0,05 | - | - |
| Strontium (Sr 2+) | mg/l | 7,0 | org. | 2 | - | - | - |
| Sulfates (SO 4 2-) | mg/l | 500 | org. | 4 | 250,0 | 250,0 | 250,0 |
| Fluorides (F) for climatic regions I and II | mg/l | 1,51,2 | social-t | 22 | 1,5 | 2,0-4,0 | 1,5 |
| Chlorides (Cl-) | mg/l | 350 | org. | 4 | 250,0 | 250,0 | 250,0 |
| Chromium (Cr 3+) | mg/l | 0,5 | social-t. | 3 | - | 0.1 (total) | - |
| Chromium (Cr 6+) | mg/l | 0,05 | social-t. | 3 | 0,05 | 0,05 | |
| Cyanide (CN-) | mg/l | 0,035 | social-t. | 2 | 0,07 | 0,2 | 0,05 |
| Zinc (Zn 2+) | mg/l | 5,0 | org. | 3 | 3,0 | 5,0 | 5,0 |
social-t. - sanitary-toxicological
org. - organoleptic
The value indicated in brackets in all tables can be established as directed by the Chief State Sanitary Doctor.
| Indicators | Units | Standards |
|---|---|---|
| Thermotolerant coliform bacteria | Number of bacteria per 100 ml | Absence |
| Common coliform bacteria | Number of bacteria per 100 ml | Absence |
| Total microbial count | Number of colony-forming bacteria in 1 ml | No more than 50 |
| Coliphages | Number of plaque-forming units (PFU) per 100 ml | Absence |
| Spores of sulforeducing clostridia | Number of spores per 20 ml | Absence |
| Giardia cysts | Number of cysts in 50 ml | Absence |
| SanPiN 2.1.4.1116 - 02 Drinking water. Hygienic requirements for the quality of water packaged in containers. Quality control. | |||
|---|---|---|---|
| Index | Unit change | highest category | First category |
| Smell at 20 degrees. WITH | point | absence | absence |
| Smell at 60 degrees. WITH | point | 0 | 1,0 |
| Chroma | degree | 5,0 | 5,0 |
| Turbidity | mg/l | < 0,5 | < 1,0 |
| pH | units | 6,5 - 8,5 | 6,5 - 8,5 |
| Dry residue | mg/l | 200 - 500 | 1000 |
| Permanganate oxidability | mgO 2 /l | 2,0 | 3,0 |
| Overall hardness | mEq/l | 1,5 - 7,0 | 7,0 |
| Iron | mg/l | 0,3 | 0,3 |
| Manganese | mg/l | 0,05 | 0,05 |
| Sodium | mg/l | 20,0 | 200 |
| Bicarbonates | mEq/l | 30 - 400 | 400 |
| Sulfates | mg/l | < 150 | < 250 |
| Chlorides | mg/l | < 150 | < 250 |
| Nitrates | mg/l | < 5 | < 20 |
| Nitrites | mg/l | 0,005 | 0,5 |
| Fluorides | mg/l | 0,6-1,2 | 1,5 |
| Petroleum products | mg/l | 0,01 | 0,05 |
| Ammonia | mg/l | 0,05 | 0,1 |
| Hydrogen sulfide | mg/l | 0,003 | 0,003 |
| Silicon | mg/l | 10,0 | 10,0 |
| Bor | mg/l | 0,3 | 0,5 |
| Lead | mg/l | 0,005 | 0,01 |
| Cadmium | mg/l | 0,001 | 0,001 |
| Nickel | mg/l | 0,02 | 0,02 |
| Mercury | mg/l | 0,0002 | 0,0005 |
| These sanitary rules do not apply to mineral waters (medicinal, medicinal - table, table). | |||
3. Optimal value of physico-chemical and microelement indicators of vodka (according to PTR 10-12292-99 with changes 1,2,3)
| Standardized indicators | For process water with hardness, mol/m 3 (maximum permissible value) | ||||
|---|---|---|---|---|---|
| 0-0,02 | 0,21-0,40 | 0,41-0,60 | 0,61-0,80 | 0,81-1,00 | |
| Alkalinity, volume of hydrochloric acid concentration with (HCl) = 0.1 mol/dm 3 used for titration of 100 cm 3 of water, cm 3 Hydrogen value (pH) |
2,5 | 1,5 | 1,0 | 0,4 | 0,3 |
| Mass concentration, mg/dm 3 - calcium - magnesium - iron - sulfates - chlorides - silicon - hydrocarbonates - sodium+potassium - manganese - aluminum - copper - phosphates - nitrates |
1,6 0,5 0,15 18,0 18,0 3,0 75 60 0,06 0,10 0,10 0,10 2,5 |
4,0 1,0 0,12 15,0 15,0 2,5 60 50 0,06 0,06 0,06 0,10 2,5 |
5,0 1,5 0,10 12,0 12,0 2,0 40 50 0,06 0,06 0,06 0,10 2,5 |
4,0 1,2 0,04 15,0 9,0 1,2 25 25 0,06 0,06 0,06 0,10 2,5 |
5,0 1,5 0,02 6,0 6,0 0,6 15 12 0,06 0,06 0,06 0,10 2,5 |
| Standardized indicators | Minimum permissible value |
|---|---|
| Hardness, mol/m 3 | 0,01 |
| Alkalinity, volume of hydrochloric acid concentration with (HCl) = 0.1 mol/dm 3 used for titration of 100 cm 3 of water, cm 3 | 0 |
| Oxidability, O 2 /dm 3 | 0,2 |
| Hydrogen value (pH) | 5,5 |
| Mass concentration, mg/dm 3 | |
| - calcium | 0,12 |
| - magnesium | 0,04 |
| - iron | 0,01 |
| - sulfates | 2,0 |
| - chlorides | 2,0 |
| - silicon | 0,2 |
| - hydrocarbonates | 0 |
| Name | Requirements according to TI 10-5031536-73-10 for water for production: | |
|---|---|---|
| beer | soft drinks | |
| pH | 6-6,5 | 3-6 |
| Cl-, mg/l | 100-150 | 100-150 |
| SO 4 2-, mg/l | 100-150 | 100-150 |
| Mg 2+ , mg/l | footprints | |
| Ca 2+ , mg/l | 40-80 | |
| K ++ Na + , mg/l | ||
| Alkalinity, mEq/l | 0,5-1,5 | 1,0 |
| Dry residue, mg/l | 500 | 500 |
| Nitrites, mg/l | 0 | footprints |
| Nitrates, mg/l | 10 | 10 |
| Phosphates, mg/l | ||
| Aluminum, mg/l | 0,5 | 0,1 |
| Copper, mg/l | 0,5 | 1,0 |
| Silicates, mg/l | 2,0 | 2,0 |
| Iron, mg/l | 0,1 | 0,2 |
| Manganese, mg/l | 0,1 | 0,1 |
| Oxidability, mg O 2 /l | 2,0 | |
| Hardness, mEq/l | < 4 | 0,7 |
| Turbidity, mg/l | 1,0 | 1,0 |
| Color, deg. | 10 | 10 |
| Heating system | ||||||
|---|---|---|---|---|---|---|
| Index | open | closed | ||||
| Network water temperature, ° C | ||||||
| 115 | 150 | 200 | 115 | 150 | 200 | |
| Font transparency, cm, no less | 40 | 40 | 40 | 30 | 30 | 30 |
| Carbonate hardness, mcg-equiv/kg: | ||||||
| at pH no more than 8.5 | 800/700 | 750/600 | 375/300 | 800/700 | 750/600 | 375/300 |
| at pH more than 8.5 | Not allowed | |||||
| Dissolved oxygen content, µg/kg | 50 | 30 | 20 | 50 | 30 | 20 |
| Content of iron compounds (in terms of Fe), µg/kg | 300 | 300/250 | 250/200 | 600/500 | 500/400 | 375/300 |
| pH value at 25°C | From 7.0 to 8.5 | From 7.0 to 11.0 | ||||
| Free carbon dioxide, mg/kg | Must be absent or within limits that ensure maintaining a pH of at least 7.0 | |||||
| Content of petroleum products, mg/kg | 1,0 | |||||
Notes:
- The numerator shows the values for solid fuel boilers, the denominator for liquid and gaseous boilers.
- For heating networks in which hot water boilers operate in parallel with boilers with brass tubes, the upper pH limit of the network water should not exceed 9.5.
- The dissolved oxygen content is indicated for network water; for make-up water it should not exceed 50 µg/kg.
| Indicator name | Standard for boilers with absolute pressure, MPa (kgf/cm2) | ||
|---|---|---|---|
| up to 1.4 (14) inclusive | 2,4 (24) | 3,9 (40) | |
| Total hardness, µmol/dm 3 (µg-eq/dm 3) | 15 * /20(15 * /20) | 10 * /15(10 * /15) | 5 * /10(5 * /10) |
| Content of iron compounds (in terms of Fe), µg/dm 3) | 300 Not standardized | 100 * /200 | 50 * /100 |
| Content of copper compounds (in terms of Cu), µg/dm 3 | Not standardized | 10 * Not standardized | |
| Dissolved oxygen content, µg/dm3 | 30 * /50 | 20 * /50 | 20 * /30 |
| pH value (at t = 25 ° C) | 8,5-9,5 ** | ||
| Nitrite content (in terms of NO 2 -), μg/dm 3 | Not standardized | 20 | |
| Content of petroleum products, mg/dm 3 | 3 | 3 | 0,5 |
* The numerator indicates values for boilers operating on liquid fuel with a local heat flow of more than 350 kW/m2, and the denominator indicates values for boilers operating on other types of fuel with a local heat flow of up to 350 kW/m2 inclusive.
** If there is a pre-liming or soda-liming phase in the additional water preparation system for industrial and heating boiler houses, as well as if the carbonate hardness of the source water is more than 3.5 mEq/dm 3 and if there is one of the water treatment phases (sodium cationization or ammonium - sodium - cationization) it is allowed to increase the upper limit of the pH value to 10.5.
When operating vacuum deaerators, it is allowed to reduce the lower limit of the pH value to 7.0.
| Indicator name | Norm |
|---|---|
| Mass concentration of the residue after evaporation, mg/dm 3, no more | 5 |
| Mass concentration of ammonia and ammonium salts (NH 4), mg/dm 3, no more | 0,02 |
| Mass concentration of nitrates (NO 3), mg/dm 3, no more | 0,2 |
| Mass concentration of sulfates (SO 4), mg/dm 3, no more | 0,5 |
| Mass concentration of chlorides (Cl), mg/dm 3, no more | 0,02 |
| Mass concentration of aluminum (Al), mg/dm 3, no more | 0,05 |
| Mass concentration of iron (Fe), mg/dm 3, no more | 0,05 |
| Mass concentration of calcium (Ca), mg/dm 3, no more | 0,8 |
| Mass concentration of copper (Cu), mg/dm 3, no more | 0,02 |
| Mass concentration of lead (Pb), %, no more | 0,05 |
| Mass concentration of zinc (Zn), mg/dm 3, no more | 0,2 |
| Mass concentration of substances reducing KMnO 4 (O), mg/dm 3, no more | 0,08 |
| Water pH | 5,4 - 6,6 |
| Specific electrical conductivity at 20 ° C, Siemens/m, no more | 5*10 -4 |
| Water parameters | Brand of water according to OST 11.029.003-80 | Water grade according to ASTM D-5127-90 standards | |||||
|---|---|---|---|---|---|---|---|
| A | B | IN | E-1 | E-2 | E-3 | E-4 | |
| Specific resistance at a temperature of 20 0 C, MOhm/cm | 18 | 10 | 1 | 18 | 17,5 | 12 | 0,5 |
| Content of organic substances (oxidizability), mg O 2 /l, no more | 1,0 | 1,0 | 1,5 | ||||
| Total organic carbon, µg/l, no more | 25 | 50 | 300 | 1000 | |||
| Content of silicic acid (in terms of SiO 3 -2), mg/l, no more | 0,01 | 0,05 | 0,2 | 0,005 | 0,01 | 0,05 | 1,0 |
| Iron content, mg/l, no more | 0,015 | 0,02 | 0,03 | ||||
| Copper content, mg/l, no more | 0,005 | 0,005 | 0,005 | 0,001 | 0,001 | 0,002 | 0,5 |
| Content of microparticles with a size of 1-5 microns, pcs/l, no more | 20 | 50 | Not a regulation | ||||
| Content of microorganisms, colonies/ml, no more | 2 | 8 | Not a regulation | 0,001 | 0,01 | 10 | 100 |
| Chlorides, µg/l, no more | 1,0 | 1,0 | 1,0 | 100 | |||
| Nickel, µg/l, no more | 0,1 | 1,0 | 2 | 500 | |||
| Nitrates, mg/l, no more | 1 | 1 | 10 | 1000 | |||
| Phosphates, mg/l, no more | 1 | 1 | 5 | 500 | |||
| Sulfate, mg/l, no more | 1 | 1 | 5 | 500 | |||
| Potassium, µg/l, no more | 2 | 2 | 5 | 500 | |||
| Sodium, µg/l, no more | 0,5 | 1 | 5 | 500 | |||
| Zinc, µg/l, no more | 0,5 | 1 | 5 | 500 | |||
9. Water quality standards for electroplating industries (according to GOST 9.314-90)
| Indicator name | Norm for category | ||
|---|---|---|---|
| 1 | 2 | 3 | |
| pH value | 6,0 - 9,0 | 6,5 - 8,5 | 5,4 - 6,6 |
| Dry residue, mg/dm 3, no more | 1000 | 400 | 5,0 * |
| General hardness, mEq/dm 3, no more | 7,0 | 6,0 | 0,35 * |
| Turbidity on a standard scale, mg/dm3, no more | 2,0 | 1,5 | - |
| Sulfates (SO 4 2-), mg/dm 3, no more | 500 | 50 | 0,5 * |
| Chlorides (Cl -), mg/dm 3, no more | 350 | 35 | 0,02 * |
| Nitrates (NO 3 -), mg/dm 3, no more | 45 | 15 | 0,2 * |
| Phosphates (PO 4 3-), mg/dm 3, no more | 30 | 3,5 | 1,0 |
| Ammonia, mg/dm3, no more | 10 | 5,0 | 0,02 * |
| Petroleum products, mg/dm 3, no more | 0,5 | 0,3 | - |
| Chemical oxygen demand, mg/dm 3, no more | 150 | 60 | - |
| Residual chlorine, mg/dm 3, no more | 1,7 | 1,7 | - |
| Surfactants (sum of anionic and nonionic), mg/dm 3, no more | 5,0 | 1,0 | - |
| Heavy metal ions, mg/dm 3, no more | 15 | 5,0 | 0,4 |
| Iron | 0,3 | 0,1 | 0,05 |
| Copper | 1,0 | 0,3 | 0,02 |
| nickel | 5,0 | 1,0 | - |
| zinc | 5,0 | 1,5 | 0,2 * |
| chromium trivalent | 5,0 | 0,5 | - |
| 15. Specific electrical conductivity at 20 ° C, S/m, no more | 2x10 -3 | 1x10 -3 | 5x10 -4 |
* Ingredient standards for category 3 water are determined according to GOST 6709.
Note. In water reuse systems, the content of harmful ingredients in purified water is allowed to be higher than in Table 1 but not higher than the permissible values in the rinsing bath after the rinsing operation (Table 2).
| Name of electrolyte component or ion | Name of the operation before which washing is carried out | Name of the electrolyte before which the rinsing is carried out | Permissible concentration of the main component in water after the washing operation with d, mg/dm 3 |
|---|---|---|---|
| Total alkalinity in terms of sodium hydroxide | - | Alkaline Sour or cyanide |
800 100 |
| Anodic oxidation of aluminum and its alloys | - | 50 | |
| Dyes (for coloring An. Oks coatings) | - | 5 | |
| Acid in terms of sulfuric acid | - | Alkaline Sour Cyanide |
100 50 10 |
| Filling and impregnation of coatings, drying | - | 10 | |
| CN - total, Sn 2+, Sn 4+, Zn 2+, Cr 6+, Pb 2+ | Interoperational washing, drying | - | 10 |
| CNS - , Cd 2+ | Interoperational washing, drying | - | 15 |
| Cu2+, Cu+ | Nickel plating Drying |
- | 2 10 |
| Ni 2+ | Copper plating Chrome plating, drying |
- | 20 10 |
| Fe 2+ | Drying | - | 30 |
| Salts of precious metals in terms of metal | Drying | - | 1 |
Notes:
- The main component (ion) of a given solution or electrolyte is taken to be the one for which the washing criterion is the greatest.
- When washing products that have particularly high requirements, the permissible concentrations of the main component can be established experimentally.
The concentrations of the main ingredients in the water leaving the galvanic production are given in Table 3
1.3. In electroplating production, water reuse systems should be used to ensure
| Indicator name | Indicator value |
|---|---|
| Mass concentration of aluminum, mg/cub. dm, no more | 0,0100 |
| Mass concentration of antimony, mg/cub. dm, no more | 0,0060 |
| Mass concentration of arsenic, mg/cub. dm, no more | 0,0050 |
| Mass concentration of barium, mg/cub. dm, no more | 0,1000 |
| Mass concentration of beryllium, mg/cub. dm, no more | 0,0004 |
| Mass concentration of cadmium, mg/cub. dm, no more | 0,0010 |
| Mass concentration of calcium, mg/cu. dm, no more | 2,0 |
| Mass concentration of chloramine, mg/cc. dm, no more | 0,1000 |
| Mass concentration of chromium, mg/cub. dm, no more | 0,0140 |
| Mass concentration of copper, mg/cub. dm, no more | 0,1000 |
| Mass concentration of cyanide, mg/cub. dm, no more | 0,0200 |
| Mass concentration of fluorides, mg/cub. dm, no more | 0,2000 |
| Mass concentration of free residual chlorine, mg/cub. dm, no more | 0,5000 |
| Mass concentration of lead, mg/cub. dm, no more | 0,0050 |
| Mass concentration of magnesium, mg/cub. dm, no more | 2,0 |
| Mass concentration of mercury, mg/cub. dm, no more | 0,0002 |
| Mass concentration of nitrates, mg/cub. dm, no more | 2,000 |
| Mass concentration of potassium, mg/cub. dm, no more | 2,0 |
| Mass concentration of selenium, mg/cub. dm, no more | 0,0050 |
| Mass concentration of sodium, mg/cu. dm, no more | 50 |
| Mass concentration of sulfates, mg/cub. dm, no more | 100 |
| Mass concentration of tin, mg/cub. dm, no more | 0,1000 |
| Mass concentration of zinc, mg/cub. dm, no more | 0,1000 |
| Specific electrical conductivity, µS/m, no more | 5,0 |
| Indicators | FS 42-2619-97 | EP IV ed. 2002 |
|---|---|---|
| Receipt methods | Distillation, ion exchange, reverse osmosis or other suitable methods | Distillation, ion exchange or other suitable methods |
| Description | Colorless transparent liquid, odorless and tasteless | |
| Source water quality | - | |
| pH | 5.0-7.0 | - |
| Dry residue | ≤0.001% | - |
| Reducing agents | Absence | Alternative TOC ≤0.1ml 0.02 KMnO 4 / 100 ml |
| Carbon dioxide | Absence | - |
| Nitrates, nitrites | Absence | ≤0.2 mg/l (nitrates) |
| Ammonia | ≤0.00002% | - |
| Chlorides | Absence | - |
| Sulfates | Absence | - |
| Calcium | Absence | - |
| Heavy metals | Absence | ≤0.1 mg/l |
| Acidity/alkalinity | - | - |
| Aluminum | - | ≤10µg/l (for hemodialysis) |
| Total organic carbon (TOC) | - | ≤0.5 mg/l |
| Specific electrical conductivity (EC) | - | ≤4.3 µS/cm (20 o C) |
| Microbiological purity | ≤100 m.o./ml | |
| - | ≤0.25 EU/ml for hemodialysis | |
| Marking | The label states that the water can be used to prepare dialysis solutions. |
| Indicators | FS 42-2620-97 | EP IV ed. 2002 |
|---|---|---|
| Receipt methods | Distillation, reverse osmosis | Distillation |
| Source water quality | - | Water, resp. drinking water requirements of the European Union |
| Microbiological purity | ≤100 m.o./ml in the absence of Enterobacteriaceae Staphylococcus aureus, Pseudomonas aeruginosa | ≤10CFU/100ml |
| Pyrogenicity | Non-pyrogenic (biological method) | - |
| Bacterial endotoxins (BE) | ≤0.25EU/ml (change No. 1), | ≤ 0.25 EU/ml |
| Electrical conductivity | - | ≤1.1 µS/cm (20 o C) |
| OOU | - | ≤0.5 mg/l |
| Use and storage | Use freshly prepared or store at a temperature from 5 o C to 10 o C or from 80 o C to 95 o C in closed containers made of materials that do not change the properties of water, protecting water from mechanical impurities and microbiological contaminants, but not more than 24 hours | Stored and distributed under conditions that prevent the growth of microorganisms and the entry of other types of contaminants. |
| Marking | The label of containers for collecting and storing water for injection must indicate “not sterilized” | - |
| Index | Unit measurements | cucumber (soil) | tomato (soil) | low-volume crop |
|---|---|---|---|---|
| Hydrogen value (pH) | units pH | 6.0 - 7.0 | 6.0 - 7.0 | 6.0 - 7.0 |
| Dry residue | mg/l | less than 500 | less than 1000 | 500 - 700 |
| Total alkalinity | mEq/l | less than 7.0 | less than 7.0 | less than 4.0 |
| Calcium | mg/l | less than 350 | less than 350 | less than 100 |
| Iron | -"- | 1,0 | 1,0 | 1,0 |
| Manganese | -"- | 1,0 | 1,0 | 0,5 |
| Sodium | -"- | 100 | 150 | 30 - 60 |
| Copper | -"- | 1,0 | 1,0 | 0,5 |
| Bor | -"- | 0,5 | 0,5 | 0,3 |
| Zinc | -"- | 1,0 | 1,0 | 0,5 |
| Molybdenum | -"- | 0,25 | 0,25 | 0,25 |
| Cadmium | -"- | 0,001 | 0,001 | 0,001 |
| Lead | -"- | 0,03 | 0,03 | 0,03 |
| Sulfates (in terms of sulfur) | -"- | 60 | 100 | 60 |
| Chlorides | -"- | 100 | 150 | 50 |
| Fluorine | mg/l | 0,6 | 0,6 | 0,6 |
Good afternoon
Tell me, is there any theoretical method for determining the conductivity of water with compounds dissolved in it, if the initial conductivity of water and the exact quantitative content of compounds dissolved in water are known.
Thank you in advance!
Accurate calculation of specific electrical conductivity is carried out using special empirical formulas using calibrated solutions of potassium chloride with a previously known value of electrical conductivity. It is customary to display the measured value using the Siemens unit of measurement, 1 cm is the inverse of 1 ohm. Moreover, for salt water the research results are displayed in S/m, and for fresh water – in µS/meter, that is, in microsiemens. Measurement of electrical conductivity of aqueous solutions gives for distilled water a SEP value from 2 to 5 μS/meter, for atmospheric precipitation a value from 6 to 30 or more μS/meter, and for fresh river and lake waters in those areas where the air environment is heavily polluted, the SEP value can vary by within 20-80 µS/cm.
To mitigate this problem, four electrodes are often used instead of two. Electrode polarization can be prevented or reduced by applying alternating current and adjusting the measurement frequency. Low frequencies are used to measure low conductivity, where the polarization resistance is relatively small. Higher frequencies are used to measure high conductivity values. Modern digital two-electrode conductivity meters typically use complex AC waveforms and temperature compensation.
To approximate the SEP, you can use the empirically found relationship between the SEP and the salt content in water (salinity):
UEP ( µS/cm ) = salt content (mg / l) / 0,65
That is, to determine the SEP (μS/cm), the salt content (water mineralization) (mg/l) is divided by a correction factor of 0.65. The value of this coefficient varies depending on the type of water in the range of 0.55-0.75. Sodium chloride solutions conduct current better: NaCl content (mg/l) = 0.53 µS/cm or 1 mg/l NaCl provides electrical conductivity of 1.9 µS/cm.
Experiment: measuring total mineralization and conductivity
They are factory calibrated and often require recalibration in the field as the cell constant changes over time. It may be altered due to contamination or physicochemical modification of the electrodes. In a traditional two-electrode conductivity meter, an alternating voltage is applied between two electrodes and the resulting current is measured. This meter, although simple, has one drawback - it measures not only the resistance of the solution, but also the resistance caused by the polarization of the electrodes.
For an approximate calculation of the UEP based on the salt content in water (salinity), you can use the following graph (Fig. 1):
Rice. 1. Graph of the dependence of the electrical energy consumption on the salt content (salinity) in water.
The electrical resistance is also measured using a special device - a conductometer, consisting of platinum or steel electrodes immersed in water, through which an alternating current with a frequency of 50 Hz (in low-mineralized water) to 2000 Hz or more (in salt water) is passed, by measuring electrical resistance .
To minimize the effects of polarization, 4-electrode cells are often used, as well as platinized cells coated with platinum black. Electrical conductivity measuring devices are often used to measure total dissolved solids. It is a measure of the total mass of all organic and inorganic substances contained in a liquid in various forms: ionized, molecular, colloidal and suspended. Dissolved solids refer to any inorganic salts, mainly calcium, potassium, magnesium, sodium, chlorides, bicarbonates and sulfates and some organic matter dissolved in water.
The principle of operation of the conductometer is based on the direct dependence of the electrical conductivity of water (current strength in a constant electric field created by the electrodes of the device) on the amount of compounds dissolved in water. A wide range of appropriate equipment now makes it possible to measure the conductivity of almost any water, from ultrapure (very low conductivity) to saturated with chemical compounds (high conductivity).
Total dissolved solids are usually measured in water to determine its quality. There are two main methods for measuring total dissolved solids: gravimetric analysis, which is the most accurate method, and conductivity measurement.
The second method is not as accurate as gravimetric analysis. However, the conductivity method is the most convenient, useful, widespread and fast method because it is a simple measurement of conductivity and temperature that can be done in a few seconds using an inexpensive device. This method can be used because the electrical conductivity of water is directly related to the concentration of ionized substances dissolved in the water. This is especially useful for quality control purposes such as monitoring drinking water or estimating the total number of ions in a solution.
A conductivity meter can even be purchased at pet stores, and combinations of such a device with a pH meter are possible. In addition, such a device can be purchased at offices and companies selling equipment for environmental research www.tdsmeter.ru/com100.html.
Craftsmen who are good with a soldering iron can make their own device for measuring the electrical conductivity of I.I. Vanyushin’s design. (magazine "Fisheries", 1990, No. 5, pp. 66-67. In addition, this device and methods for its calibration are described in all details in the very useful book "Modern Aquarium and Chemistry", authors I.G. Khomchenko , A.V. Trifonov, B.N. Razuvaev, Moscow, 1997). The device is made on the common K157UD2 microcircuit, which consists of two operational amplifiers. The first one houses an alternating current generator, the second one houses an amplifier according to a standard circuit, from which readings are taken with a digital or analog voltmeter (Fig. 2).
Production and quality control of distilled water
Conductivity measurements are temperature dependent, i.e. As the temperature increases, conductivity also increases because the ions in the solution move faster. To obtain temperature-independent measurements, the concept of reference temperature was introduced. This allows conductivity results to be compared at different temperatures. If very high accuracy is required, the sample can be placed in an oven and the meter will then be calibrated to the exact same temperature used for the measurement.
Rice. 2. Homemade conductivity meter.
To eliminate the influence of temperature, electrical conductivity measurements are carried out at a constant temperature of 20 0 C, since the value of electrical conductivity and the measurement result depend on temperature, as soon as the temperature increases by at least 1 0 C, the measured value of electrical conductivity also increases by approximately 2%. Most often, it is recalculated in relation to 20 0 C according to the correction table, or reduced to it using empirical formulas.
Most modern conductivity meters contain a built-in temperature sensor that can be used for temperature correction as well as temperature measurement. However, they all only measure conductivity and temperature, and then calculate the required physical value and perform temperature compensation.
The same brand name device, probably made in the same factory, would cost 10 times more. But this is for those who like to pay only for the brand name. It should be noted that the two actual physical values that this device measures are the resistance of the solution between the two electrodes and the temperature of the solution.
Correction table for calculating UEP.
Temperature, °C | Correction factor | Temperature, °C | Correction factor | Temperature, °C | Correction factor |
The calculation of the specific electrical conductivity of water in this case is carried out using the formula :
This is a dimensionless quantity. Just as percentage means out of a hundred, parts per million units means out of a million. We will discuss these calculations below. Examples of substances with high salt concentrations are some foods and sea water. This is only the normal concentration of salt in many foods.
There are many different scales in many industries. The difference between them lies in their use. For our experiment, we will first measure the total dissolved solids in distilled water. To prepare 100 ml of solution, we need 100 mg of sodium chloride and up to 100 ml of distilled water. To make the solution, we place sodium chloride in a measuring cylinder, add some distilled water and stir until the sodium chloride is completely dissolved. Then add distilled water to the 100 ml mark and mix well again.
UEP = C p / R
where C p is the capacitance of the device sensor, which depends on the material and size of the electrodes and has a dimension of cm-1, determined by calibrating the device using solutions of potassium chloride with a known value of electrical conductivity; K is the temperature coefficient for bringing the measured value at any temperature to its accepted constant value; R is the measured electrical resistance of water by the device, in Ohms.
This is slightly less than the value of 5 cm-1. Note that the formula for calculating the cell constant can only give an approximate value. Do you have difficulty translating a unit of measurement into another language? Electrical conductivity estimates the amount of all dissolved salts or the total number of dissolved ions in water.
What in the world are microspheres per centimeter? These are units of electrical conductivity. The sensor simply consists of two metal electrodes that are exactly 0 cm apart and protrude into the water. A constant voltage is applied to the electrodes. Electrical current flows through the water due to this voltage and is proportional to the concentration of dissolved ions in the water - the more ions, the more conductive the water results in a higher electrical current, which is measured electronically. Distilled or deionized water has very few dissolved ions and therefore almost no current flowing through the gap.
The device must be calibrated in resistance values. For calibration, the following resistances can be recommended: 1 kOhm (electrical conductivity 1000 µS), 4 kOhm (250 µS), 10 kOhm (100 µS).
In order to more accurately determine the specific electrical conductivity, you need to know the constant of the vessel for measuring CX. To do this, it is necessary to prepare a 0.01 M solution of potassium chloride (KCl) and measure its electrical resistance R KCl, (in kOhm) in the prepared cell. The capacity of the vessel is determined by the formula:
Classification of salt waters
You will find both sets of units in published scientific literature, although their numerical values are identical. It is simply a scale symbol, from 0 to 14, that rates aqueous solutions based on their acidity or alkalinity. Pure water is given the number 7 - right in the middle of the scale - because it contains equal amounts of acidic and basic ions and is therefore neutral. As the alkalinity of a solution increases, the pH value increases; As acidity increases, pH decreases. Each step represents an increase or decrease by a factor of ten.
C p = R KC UEP KCl
where SEP KC is the specific electrical conductivity of a 0.01 M KCl solution at a given temperature in μS/cm, found from the correction table.
The UEP is then calculated using the formula:
UEP =C P (K T )/R
The pH of a water sample is a measure of the concentration of hydrogen ions. The term pH was derived from how the concentration of hydrogen ions is calculated - it is the negative logarithm of the concentration of hydrogen ions. What this means for those of us who are not mathematicians is that at higher pH there are fewer free hydrogen ions and that a change in one unit of pH represents a tenfold change in hydrogen ion concentrations. For example, the number of hydrogen ions is 10 times greater at pH 7 than at pH 7.
Establishing the value of total water mineralization
The pH range from 0 to a pH of 7 is considered neutral. Substances with a pH less than 7 are acidic; substances with a pH greater than 7 are basic. For example, in addition to influencing how much and what form of phosphorus is most abundant in water, pH can also determine whether aquatic life can use it. In the case of heavy metals, the degree of their solubility determines their toxicity.
where C p is the capacitance of the device sensor, which depends on the material and size of the electrodes and has a dimension of cm -1, is determined by calibrating the device using solutions of potassium chloride with a known value of the electrical conductivity; K t - temperature coefficient for bringing the measured value at any temperature to its accepted constant value; R is the measured electrical resistance of water by the device, in Ohms.
Metals tend to be more toxic at lower pH because they are more soluble. No need to adjust normally Easy to operate Reliable and stable Easy to carry. Deionized water is often used for precision cleaning. It's a proven process, but with a number of hidden pitfalls.
In general, there are three general levels of water: tap water, distilled water, and deionized water. From a precision cleaning standpoint, neither tap water nor distilled water are clean enough to do the job, as they are contaminated to a greater or lesser extent with minerals and organic matter.
The SEP of salt water is usually expressed in S/m (Sm - Siemens, the reciprocal of Ohm), for fresh water - in microsiemens (µS/cm). The SER of distilled water is 2-5 µS/cm, atmospheric precipitation - from 6 to 30 µS/cm or more, in areas with heavily polluted air, river and fresh lake waters 20-800 µS/cm.
The normalized mineralization values approximately correspond to a specific electrical conductivity of 2 mS/cm (1000 mg/dm 3) and 3 mS/cm (1500 mg/dm 3) in the case of both chloride (in terms of NaCl) and carbonate (in terms of CaCO 3 ). mineralization.
Double-strand deionizers use separate tanks, one containing a cationic resin and another containing an anionic resin. Obviously, costs, energy consumption, end-to-end and control issues will increase exponentially as water purity increases. The purer the water, the hungrier it is for ions, and the more contaminants it will attract unless packaging and processing are tightly controlled.
Now you haven't specified any specifics of the application you were working on. If the water is clean enough to be a harsh cleaner, it will instantly become dirty as soon as the bottle or container is opened, at which point you can also clean with distilled water and save some money.
Pure water, as a result of its own dissociation, has a specific electrical conductivity at 25 C equal to 5.483 µS/m.
For more information about the methods for calculating the UEP, see the relevant sections of our website.
Ph.D. O.V. Mosin
Below are methodological methods for calculating total mineralization, ionic strength, hardness and determining the content of sulfate ions in natural and waste waters based on specific electrical conductivity as a general indicator of their quality.
This was because they found that after an hour or so the cleaning stopped no matter how long they ran the machines. The only viable option is a tightly closed loop system that treats the water, performs the treatment, and then recycles the water. They tend to be expensive, power hungry, and relatively slow end-to-end.
The reverse osmosis filter removes additional contaminants, while the mixed bed resin filter removes the final dissolved minerals. If you are cleaning high quality semiconductor final cleaning of optics or high end medical devices, then Type 1 is the right choice.
Determining the electrical conductivity (L) of water comes down to measuring its inverse value - the resistance (R) that water provides to the current passing through it. Thus, L= 1:R, and therefore the electrical conductivity value is expressed in inverse Ohms, and according to the modern SI classification - in Siemens (Sm).
The value of specific electrical conductivity remains unchanged within the permissible error (10%) in the presence of organic compounds of various natures (up to 150 mg/dm3) and suspended substances (up to 500 mg/dm3) in natural and waste waters.
How filtration and reverse osmosis systems work. Cartridge filter Next is the cartridge type filter. This type of filter usually has a removable housing into which different types of "elements" can be placed. The sediment filter cartridge element can be manufactured to remove particles of a certain size or larger. Most industrial and laboratory use items indicate removal of 15 to 15 microns or more. and add after it the words “Absolute”. This simply means that if it says it is 5 microns, it means!
To measure specific electrical conductivity (xi), any conductivity meters with a range from 1*10(-6) S/cm to 10*10(-2) S/cm can be used.
1. PRODUCTION AND QUALITY CONTROL OF DISTILLED WATER
1.1. QUALITY STANDARDS
In laboratories for quality control of natural and waste waters, distilled water is the main solvent for the preparation of reagents, a diluent for test samples, an extractant, and is also used for rinsing laboratory glassware. Therefore, for the successful operation of any chemical analytical laboratory, along with the fulfillment of such conditions as highly qualified specialists, the availability of accurate verified instruments, the use of reagents of the required degree of purity, standard samples and standard measuring glassware, great attention should be paid to the quality of distilled water, which in its own way physical and chemical parameters must comply with the requirements of GOST 670972 (see table).
STANDARDS
QUALITY OF DISTILLED WATER BY
pH ¦ 5.4-6.6 ¦
Substances that reduce KMnO4 ¦ 0.08 ¦
Residue after evaporation ¦ 5.0 ¦
Residue after ignition ¦ 1.0 ¦
Ammonia and ammonium salts ¦ 0.02 ¦
Nitrates ¦ 0.20 ¦
Sulfates ¦ 0.50 ¦
Chlorides ¦ 0.02 ¦
Aluminum ¦ 0.05 ¦
Iron ¦ 0.05 ¦
Calcium ¦ 0.80 ¦
Copper ¦ 0.02 ¦
Lead ¦ 0.05 ¦
Zinc ¦ 0.20 ¦
Specific electrical conductivity at 20 degrees. C no more than 5*10(-6) cm/cm
If all indicators comply with established standards, then distilled water is suitable for use in laboratory research, and its quality will not affect the metrological characteristics of analyzes performed in the laboratory. Standards for the frequency of quality control of distilled water have not been established.
1.2. RECEIVING AND QUALITY CONTROL
Distilled water is obtained in various brands of distillers. The distiller is installed in a separate room, the air of which should not contain substances that are easily absorbed by water (ammonia vapor, hydrochloric acid, etc.). During the initial start-up or when starting up the distiller after long-term preservation, the use of distilled water is permitted only after 40 hours of operation of the distiller and after checking the quality of the resulting water in accordance with GOST requirements.
Depending on the composition of the source water, distilled water of various qualities can be obtained.
With a high content of calcium and magnesium salts in water, scale forms on the surface of the heating elements, the internal walls of the steam generator and the refrigerating chamber, resulting in deterioration of heat exchange conditions, leading to a decrease in productivity and a shortening of the service life of the distiller. In order to soften the source water and reduce the formation of scale, it is advisable to operate the device in combination with an anti-scale magnetic device or a chemical water conditioner (based on ion-exchange resins in sodium form), for example the KU-2-8chs brand.
The question of the timing of periodic preventive flushing of the distiller and descaling is decided experimentally, guided by data on the quality of distilled water during periodic monitoring. After cleaning and washing the distiller, distilled water is again analyzed for all indicators in accordance with GOST.
All results of water tests should be entered into a journal, where at the same time it is necessary to reflect the operating mode of the distiller. Analysis of the results obtained will make it possible to establish for each source water its own mode of operation of the device: the period of operation, the period of its shutdown for preventive cleaning, washing, rinsing, etc.
If water with a high content of organic substances is used as source water, then some of them can be distilled into the distillate and increase the control value of oxidation. Therefore, GOST provides for the determination of the content of organic substances that reduce potassium permanganate.
To free the distilled water from organic impurities and improve the quality of the distillate, it is recommended to use chemical water conditioners with granulated sorbent made of birch activated carbon or with macroporous granulated anion exchanger brand AB-17-10P.
If substances that reduce potassium permanganate in a concentration of more than 0.08 mg/dm are detected in distilled water, it is necessary to carry out a secondary distillation of the distillate by adding 1% KMnO4 to it before distilling off the solution, at the rate of 2.5 cm3 per 1 dm of water. The total time spent on monitoring the quality of distilled water for all 14 indicators indicated in the table is 11 hours of analyst working time (65 laboratory units). Determining the specific electrical conductivity of water compares favorably in terms of time costs with traditional chemical analysis when determining individual indicators, because the time required for its determination is no more than 1 laboratory unit (10 minutes) and is recommended as an express method for monitoring the quality of distilled water.
Based on the value of specific electrical conductivity, one can generally characterize the entire sum of the components of the residual amount of mineral substances (including nitrates, sulfates, chlorides, aluminum, iron, copper, ammonia, calcium, zinc, lead).
If it is necessary to obtain express information about the content of sulfate ions in water, the latter can be calculated from the value of specific electrical conductivity and the content of hydrocarbonate chloride ions (see section 2).
According to GOST, the result of the intended value of distilled water is expressed at 20 degrees. WITH
1.3. STORAGE CONDITIONS
Distilled water for laboratory tests must be freshly distilled. If necessary, water can be stored in hermetically sealed polyethylene or fluoroplastic bottles. To prevent the absorption of carbon dioxide from the air, bottles with distilled water must be closed with stoppers with calcium chloride tubes. Ammonia-free water is stored in a bottle closed with a stopper with a “goose” containing a solution of sulfuric acid.
3. ESTABLISHING THE VALUE OF TOTAL MINERALIZATION OF WATER
3.1. NATURAL WATERS
One of the most important indicators of water quality is the value of total mineralization, usually determined gravimetrically from the dry residue. Using chemical analysis data on the content of chloride and hydrocarbonate sulfate ions, using conversion factors, it is possible to calculate the value of total mineralization (M, mg/dm3) of the water under study using formula (2):
M=[HCO(3-)*80+[Cl-]-55+*67
where [HCO(3-)], [Cl], are the concentrations of bicarbonate, chloride, and sulfate ions in mEq/dm.cub. respectively. The numerical factors approximately correspond to the arithmetic mean values of the molar masses of the equivalents of salts of the corresponding anion with calcium, magnesium, sodium and potassium.
3. METHOD FOR ASSESSING THE IONIC STRENGTH OF AN AQUEOUS SOLUTION
In the practice of hydrochemical research, the value of the ionic strength of water is used to control the ionic composition of water using ion-selective electrodes, as well as in the express calculation of total hardness.
Calculation of the ionic strength (mu) of natural and waste waters is made based on the results of double measurements of the specific electrical conductivity of water: undiluted (xi1) and diluted in a ratio of 1:1 (xi2).
The ionic strength is calculated using formula (4):
(mu)=K*Cm10 (4)
Where Cm is the total mineralization of water, calculated from the specific electrical conductivity as a * 10(4) and expressed in mEq/dm3;
K is the ion indicator, established using an adjustment table based on the values of Cm and xi2/xi1.
The values (mu) of natural and waste waters (even those containing a large amount of suspended particles) calculated by this method are consistent with the values (mu) determined from chemical analysis of the content of major ions; the discrepancy between the results of the two methods does not exceed 10%, which is consistent with the acceptable reproducibility standards.
This rapid method for determining the ionic strength of natural and waste waters is more economical and has an advantage in monitoring turbid and colored waters.
4. METHOD FOR ASSESSING THE TOTAL HARDNESS OF WATER
Displacement hardness is one of the most important group indicators of water quality for all types of water use. The generally accepted complex metric determination of hardness has a significant limitation and cannot be used when analyzing turbid and colored waters, as well as when there is a significant content of a number of metals. When determining the total hardness, such waters must undergo special treatment, which is associated with an increase in the consumption of chemical reagents and additional costs of working time for analysis.
An accelerated method for estimating the approximate value of total hardness (W total) is based on data obtained from electrical conductivity measurements. The calculation is made using the formula (5)%
F total = 2(mu) * 10(3) - (2Sm + SO4(2-)]) (5)
where (mu) is the value of the ionic strength of water (calculation based on electrical conductivity data, see section 4); cm - total mineralization, mEq/dm.cub. (calculation based on electrical conductivity data, see section 4); - concentration of sulfate ions, mEq/dm.cub. (calculation based on electrical conductivity data, see section 2, or another method). The error in determining rigidity using this method is within acceptable limits (5%). The method is recommended as an accelerated method for assessing total hardness in conditions of mass analysis of samples in an environmental monitoring system, especially in the case of turbid, colored waters and waters heavily contaminated with ions of a number of heavy metals.
LITERATURE
GOST 6709-72 "Distilled water".
Instructions for the organization and structure of laboratory control in the system of the Ministry of Housing and Communal Services of the RSFSR. M. 1986.
Vorobiev I.I. Application of electrical conductivity measurements to characterize the chemical composition of natural waters. M., Publishing House of the USSR Academy of Sciences, 1963-141 p.
Pochkin Yu.N. Determination of electrical conductivity of water when studying the salt regime of open reservoirs // Hygiene and Sanitation. 1967, N 5.
GOST 17403-72. Hydrochemistry. Basic concepts. Terms and Definitions.
Lurie Yu.Yu. Analytical chemistry of industrial wastewater. M., Chemistry, 1984.-447 p.
RD 52.24.58-88. Methodology for measuring the content of sulfate ions using the titrimetric method with barium salt.
RD 52.24.53-88. Methodology for measuring the content of sulfate ions with lead salt.
GOST 27384-87. Water. Measurement error standards are indicative of composition and properties.
GOST 26449.1-85. Stationary distillation and desalination plants. Methods of chemical analysis of salt waters.
Information leaflet N 29-83. Determination of boiler water content. CSTI, Arkhangelsk. 1983.
Manual for the chemical analysis of terrestrial surface waters. L., Gidrometeoizdat. 1977. - 537 p.
Accelerated determination of total mineralization, total hardness, ionic strength, content of sulfate ions and free CO2 by electrical conductivity. Kazan. GIDUV. 1989. - 20 p.
The product of the concentrations of hydrogen and hydroxyl ions in chemically pure water is a constant value equal to 10 -14 at a temperature of 25 °C. It remains unchanged in the presence of substances that dissociate to form hydrogen and hydroxyl ions. In pure water, the concentrations of hydrogen and hydroxyl ions are 10 -7 mol/dm 3, which corresponds to the neutral state of the solution. In acidic solutions [H + ] > 10 -7 mol/dm 3, and in alkaline solutions [H + ]
For convenience, expressing the concentration of hydrogen ions in water uses a value that is the decimal logarithm of their concentration taken with the opposite sign. This quantity is called pH value and is designated pH(pH = - log ¢).
The pH value is one of the most important indicators of water quality and characterizes the state of acid-base balance of water. The development and vital activity of aquatic biota, the forms of migration of various elements, and the aggressive effect of water on host rocks, metals, and concrete depend on the pH value.
The pH value of surface waters is influenced by the state of carbonate equilibrium, the intensity of the processes of photosynthesis and decay of organic substances, and the content of humic substances.
In most water bodies, the pH of the water usually ranges from 6.3 to 8.5. In river and lake waters, pH values are lower in winter compared to summer.
The pH value of surface waters subject to intense pollution by wastewater or the influence of groundwater may vary within wider limits due to the presence of strong acids or bases in their composition.
Specific electrical conductivity (electrical conductivity) - quantitative characteristic of water’s ability to conduct electric current. In a purely physical sense, this is the reciprocal of the electrical resistance of water at a temperature of 25 ° C, located between two electrodes with a surface of 1 cm 2, the distance between which is 1 cm. The unit of electrical conductivity is Siemens per 1 m (S/m). For water, derived values are used as a unit of measurement - milliSiemens per 1 m (mS/m) or microSiemens per 1 cm (μS/cm).
In most cases, the specific electrical conductivity of land surface waters is an approximate characteristic of the concentration of inorganic electrolytes in water - Na +, K +, Ca 2+, Mg 2+ cations and Clˉ, SO 4 2-, HCO 3 - anions . The presence of other ions, e.g. Fe (II), Fe (III), Mn (II), NO 3 - , HPO 4 2- usually has little effect on the value of electrical conductivity, since these ions are rarely found in water in significant quantities. Hydrogen and hydroxyl ions in the range of their usual concentrations in surface waters of land have practically no effect on the electrical conductivity. The influence of dissolved gases is equally small.
Thus, the specific electrical conductivity of land surface waters depends mainly on their mineralization and usually ranges from 50 to 10,000 µS/cm.
The pH of water is measured potentiometrically, and the specific electrical conductivity is measured by the conductometric method using appropriate instruments - pH meters (ionomers) and conductometers. Modern devices (ionomers-salin meters) are equipped with sensors for both indicators and allow them to be measured almost simultaneously.
RD 52.24.495-2005
GUIDANCE DOCUMENT
HYDROGEN INDICATOR AND SPECIFIC ELECTRICAL CONDUCTIVITY OF WATER. METHOD OF PERFORMING MEASUREMENTS USING THE ELECTROMETRIC METHOD
Date of introduction 2005-07-01
Application area
This guidance document establishes methods for performing measurements (hereinafter referred to as the method) of the hydrogen index in the range from 4 to 10 units. pH and electrical conductivity in the range from 5 to 10,000 µS/cm in samples of land surface waters and treated wastewater by electrometric method.
Measurement error characteristics
Measurement method
When measuring the pH of water using the electrometric method, a system is used that consists of a glass electrode, the potential of which depends on the concentration (activity) of hydrogen ions, and an auxiliary electrode. When immersed in a water sample, the electrode system develops an emf that linearly depends on the activity of hydrogen ions.
The measurement of electrical conductivity is based on measuring the electrical resistance of a solution located between two platinum (platinized) electrodes with a surface area of 1 cm 2, the distance between which is 1 cm.
When the temperature changes by 1 °C, the value of the specific electrical conductivity changes (increases with increasing temperature) by approximately 2%. Therefore, to eliminate this error, measurements are carried out in a temperature-controlled sample or using an automatic temperature compensator. Otherwise, appropriate corrections are made to the results.
Safety and environmental requirements
where v t is the value of specific electrical conductivity at measurement temperature, µS/cm;
f - temperature correction (Appendix).
If the device is calibrated in other units, the measurement result must be converted to microsiemens per centimeter.
where pH is the arithmetic mean of two results, the difference between which does not exceed the repeatability limit r (0.06 pH units).
where: v is the arithmetic mean of two results, the difference between which does not exceed the repeatability limit r (2.77 s r);
± D - limits of measurement error ( table).
In this case, the actual measurement temperature is indicated if automatic or mathematical correction of the result was carried out. The numerical values of the measurement result must end with a digit of the same digit as the values of the error characteristic.
Quality control of measurement results when implementing the technique in the laboratory
When implementing the technique in the laboratory, the following is provided:
Operational control by the performer of the measurement procedure (based on an assessment of repeatability when implementing a separate control procedure);
Monitoring the stability of measurement results (based on monitoring the stability of the standard deviation of repeatability).
The algorithm for operational control by the performer of the measurement procedure is given in RD 52.24.495-2005.
The frequency of operational monitoring and procedures for monitoring the stability of measurement results are regulated in the Laboratory Quality Manual.
Chief metrologist of the State Chemical Institute A.A. Nazarova
