What is specific conductivity measured in? Electrical conductivity

Electrical conductivity characterizes the body's ability to conduct electric current. Conductivity - resistance value. In the formula, it is inversely proportional to electrical resistance, and they are actually used to designate the same properties of the material. Conductivity is measured in Siemens: [Sm]=.

Types of electrical conductivity:

— Electronic conductivity, where the charge carriers are electrons. This conductivity is primarily characteristic of metals, but is present to one degree or another in almost any material. As temperature increases, electronic conductivity decreases.

— Ionic conductivity. It exists in gaseous and liquid media where there are free ions that also carry charges, moving throughout the volume of the medium under the influence of an electromagnetic field or other external influence. Used in electrolytes. As temperature increases, ionic conductivity increases as more high-energy ions are produced and the viscosity of the medium decreases.

— Hole conductivity. This conductivity is caused by a lack of electrons in the crystal lattice of the material. In fact, electrons again transfer charge here, but they seem to move along the lattice, occupying sequentially free spaces in it, in contrast to the physical movement of electrons in metals. This principle is used in semiconductors, along with electronic conductivity.

Historically, the very first materials that began to be used in electrical engineering were metals and dielectrics (insulators that have low electrical conductivity). Semiconductors are now widely used in electronics. They occupy an intermediate position between conductors and dielectrics and are characterized by the fact that the amount of electrical conductivity in semiconductors can be regulated by various influences. Most modern conductors are made from silicon, germanium and carbon. In addition, other substances can be used to make PP, but they are used much less frequently.

Current transmission with minimal losses is important. In this regard, metals with high electrical conductivity and, accordingly, low electrical resistance play an important role. The best in this regard is silver (62,500,000 S/m), followed by copper (58,100,000 S/m), gold (45,500,000 S/m), aluminum (37,000,000 S/m). In accordance with economic feasibility, aluminum and copper are most often used, while copper is slightly inferior in conductivity to silver. All other metals are of no industrial importance for the production of conductors.

Electrical conductivity of water is a very important property of water for each of us.

Every person should know that water, as a rule, is electrically conductive. Ignorance of this fact can lead to detrimental consequences for life and health.

Let us give several definitions to the concept of electrical conductivity, in general, and the electrical conductivity of water in particular.

Electrical conductivity is...

A scalar quantity that characterizes the electrical conductivity of a substance and is equal to the ratio of the density of the electrical conduction current to the electric field strength.

The property of a substance to conduct a time-invariant electric current under the influence of a time-invariant electric field.

Ushakov's Explanatory Dictionary

Electrical conductivity (electrical conductivity, pl. no, female (physical)) – the ability to conduct, transmit electricity.

Ushakov's explanatory dictionary. D.N. Ushakov. 1935-1940

Big Polytechnic Encyclopedia

Electrical conductivity or Electrical conductivity is the property of a substance to conduct, under the influence of an unchanging electric field, an electric current that does not change over time. Electromagnetic energy is caused by the presence of mobile electric charges in a substance - current carriers. The type of current carrier is determined by electron (for metals and semiconductors), ionic (for electrolytes), electron-ion (for plasma) and hole (together with electron) (for semiconductors). Depending on the specific electrical conductivity, all bodies are divided into conductors, semiconductors and dielectrics, physical. the reciprocal of electrical resistance. The SI unit of electrical conductivity is siemens (q.v.); 1 cm = 1 ohm-1.

Big Polytechnic Encyclopedia. – M.: Peace and Education. Ryazantsev V.D.. 2011

The electrical conductivity of water is...

Polytechnic terminological explanatory dictionary

Electrical conductivity of water is an indicator of the conductivity of electric current by water, characterizing the salt content in water.

Polytechnic terminological explanatory dictionary. Compilation: V. Butakov, I. Fagradyants. 2014

Marine encyclopedic reference book

Electrical conductivity of sea water is the ability of sea water to conduct current under the influence of an external electric field due to the presence of electrical charge carriers in it - ions of dissolved salts, mainly NaCl. The electrical conductivity of sea water increases in proportion to the increase in its salinity and is 100 - 1000 times greater than that of river water. It also depends on the water temperature.

Marine encyclopedic reference book. - L.: Shipbuilding. Edited by Academician N. N. Isanin. 1986

From the above definitions, it becomes obvious that the electrical conductivity of water is not a constant, but depends on the presence of salts and other impurities in it. For example, the electrical conductivity of water is minimal.

How to find out the electrical conductivity of water, how to measure it...

Conductometry - measuring the electrical conductivity of water

To measure the electrical conductivity of water, the Conductometry method is used (see definitions below), and the devices used to measure electrical conductivity have a name that is consonant with the method - Conductometers.

Conductometry is...

Explanatory dictionary of foreign words

Conductometry and many others. no, w. (German: Konduktometrie
Explanatory dictionary of foreign words by L. P. Krysin. - M: Russian language, 1998

encyclopedic Dictionary

Conductometry (from the English conductivity - electrical conductivity and the Greek metreo - I measure) is an electrochemical method of analysis based on measuring the electrical conductivity of solutions. They are used to determine the concentration of solutions of salts, acids, bases, and to control the composition of some industrial solutions.

Encyclopedic Dictionary. 2009

Specific conductivity of water

And in conclusion, we present several values of specific electrical conductivity for various types of water*.

The specific electrical conductivity of water is...

Technical Translator's Guide

Specific electrical conductivity of water is the electrical conductivity of a unit volume of water.

[GOST 30813-2002]

Specific electrical conductivity of water *:

Tap water – 36.30 µS/m;
– 0.63 µS/m;
Drinking (bottled) – 20.2 µS/m;
Drinking frozen – 19.3 µS/m;
Water-frozen – 22 µS/m.

* Article “Electrical conductivity of drinking water samples of different degrees of purity” Authors: Vorobyova Lyudmila Borisovna. Magazine: “Interexpo Geo-Siberia Issue No. -5 / volume 1 / 2012.”

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1 microsiemens per centimeter [µS/cm] = 0.0001 siemens per meter [S/m]

Initial value

Converted value

siemens per meter picosiemens per meter mo per meter mo per centimeter abmo per meter abmo per centimeter statmo per meter statmo per centimeter siemens per centimeter millisiemens per meter millisiemens per centimeter microsiemens per meter microsiemens per centimeter conventional unit of electrical conductivity conventional coefficient of electrical conductivity ppm, coefficient. recalculation 700 ppm, coefficient. recalculation 500 ppm, coefficient. recalculation 640 TDS, ppm, coefficient. recalculation 640 TDS, ppm, coefficient. recalculation 550 TDS, ppm, coefficient. recalculation 500 TDS, ppm, coefficient. recalculation 700

More about electrical conductivity

Introduction and Definitions

Specific electrical conductivity (or electrical conductivity) is a measure of a substance's ability to conduct electric current or move electrical charges within it. This is the ratio of current density to electric field strength. If we consider a cube of conductive material with a side of 1 meter, then the conductivity will be equal to the electrical conductivity measured between two opposite sides of this cube.

Specific conductivity is related to conductivity by the following formula:

G = σ(A/l)

Where G- electrical conductivity, σ - specific electrical conductivity, A- cross-section of the conductor perpendicular to the direction of the electric current and l- length of the conductor. This formula can be used with any cylinder or prism shaped conductor. Note that this formula can also be used for a rectangular parallelepiped, because it is a special case of a prism, the base of which is a rectangle. Let us recall that electrical conductivity is the reciprocal of electrical resistivity.

It can be difficult for people far from physics and technology to understand the difference between the conductivity of a conductor and the specific conductivity of a substance. Meanwhile, of course, these are different physical quantities. Conductivity is a property of a given conductor or device (such as a resistor or plating bath), while conductivity is an inherent property of the material from which that conductor or device is made. For example, the conductivity of copper is always the same, no matter how the shape and size of a copper object changes. At the same time, the conductivity of a copper wire depends on its length, diameter, mass, shape and some other factors. Of course, similar objects made from materials with higher conductivity have higher conductivity (though not always).

In the International System of Units (SI), the unit of electrical conductivity is Siemens per meter (S/m). The unit of conductivity included in it is named after the German scientist, inventor, and entrepreneur Werner von Siemens (1816–1892). Founded by him in 1847, Siemens AG (Siemens) is one of the largest companies producing electrical, electronic, energy, transport and medical equipment.

The range of electrical conductivities is very wide: from materials with high resistivity such as glass (which, by the way, conducts electricity well if heated red) or polymethyl methacrylate (plexiglass) to very good conductors such as silver, copper or gold. Electrical conductivity is determined by the number of charges (electrons and ions), the speed at which they move, and the amount of energy they can carry. Aqueous solutions of various substances, which are used, for example, in plating baths, have average conductivity values. Another example of electrolytes with average conductivity values is the internal environment of the body (blood, plasma, lymph and other fluids).

The conductivity of metals, semiconductors and dielectrics is discussed in detail in the following articles of the Physical Quantity Converter website: , and Electrical conductivity. In this article we will discuss in more detail the specific conductivity of electrolytes, as well as methods and simple equipment for measuring it.

Specific electrical conductivity of electrolytes and its measurement

The specific conductivity of aqueous solutions in which an electric current arises as a result of the movement of charged ions is determined by the number of charge carriers (the concentration of the substance in the solution), the speed of their movement (the mobility of ions depends on temperature) and the charge they carry (determined by the valency of the ions). Therefore, in most aqueous solutions, an increase in concentration leads to an increase in the number of ions and, consequently, to an increase in conductivity. However, after reaching a certain maximum, the specific conductivity of the solution may begin to decrease with a further increase in the concentration of the solution. Therefore, solutions with two different concentrations of the same salt can have the same conductivity.

Temperature also affects conductivity because as temperature increases, ions move faster, resulting in increased conductivity. Pure water is a poor conductor of electricity. Ordinary distilled water, which contains carbon dioxide from the air in equilibrium and a total mineralization of less than 10 mg/l, has a specific electrical conductivity of about 20 mS/cm. The specific conductivity of various solutions is given in the table below.

To determine the specific conductivity of a solution, a resistance meter (ohmmeter) or conductivity is used. These are almost identical devices, differing only in the scale. Both measure the voltage drop across the section of the circuit through which electric current flows from the device's battery. The measured conductivity value is manually or automatically converted into specific conductivity. This is done taking into account the physical characteristics of the measuring device or sensor. Conductivity sensors are simple: they are a pair (or two pairs) of electrodes immersed in an electrolyte. Sensors for measuring conductivity are characterized by conductivity sensor constant, which in the simplest case is defined as the ratio of the distance between the electrodes D to the area (electrode) perpendicular to the current flow A

This formula works well if the area of the electrodes is significantly larger than the distance between them, since in this case most of the electrical current flows between the electrodes. Example: for 1 cubic centimeter of liquid K = D/A= 1 cm/1 cm² = 1 cm⁻¹. Note that conductivity sensors with small electrodes spaced apart over a relatively large distance are characterized by sensor constant values of 1.0 cm⁻¹ and higher. At the same time, sensors with relatively large electrodes located close to each other have a constant of 0.1 cm⁻¹ or less. The sensor constant for measuring electrical conductivity of various devices ranges from 0.01 to 100 cm⁻¹.

Theoretical sensor constant: left - K= 0.01 cm⁻¹, right - K= 1 cm⁻¹

To obtain the conductivity from the measured conductivity, the following formula is used:

σ = K ∙ G

σ - specific conductivity of the solution in S/cm;

K- sensor constant in cm⁻¹;

G- conductivity of the sensor in siemens.

The sensor constant is not usually calculated from its geometric dimensions, but is measured in a specific measuring device or in a specific measuring setup using a solution of known conductivity. This measured value is entered into the conductivity meter, which automatically calculates the conductivity from the measured conductivity or resistance values of the solution. Due to the fact that conductivity depends on the temperature of the solution, devices for measuring it often contain a temperature sensor that measures the temperature and provides automatic temperature compensation of the measurements, that is, normalizing the results to a standard temperature of 25 ° C.

The simplest way to measure conductivity is to apply a voltage to two flat electrodes immersed in a solution and measure the current flowing. This method is called potentiometric. According to Ohm's law, conductivity G is the ratio of current I to voltage U:

However, not everything is as simple as described above - there are many problems when measuring conductivity. If direct current is used, the ions collect at the surfaces of the electrodes. Also, a chemical reaction may occur at the surfaces of the electrodes. This leads to an increase in polarization resistance on the electrode surfaces, which in turn leads to erroneous results. If you try to measure the resistance of, for example, a sodium chloride solution with a conventional tester, you will clearly see how the readings on the display of a digital device change quite quickly in the direction of increasing resistance. To eliminate the influence of polarization, a sensor design of four electrodes is often used.

Polarization can also be prevented or, in any case, reduced, if you use alternating current instead of direct current when measuring, and even adjust the frequency depending on the conductivity. Low frequencies are used to measure low conductivity, where the influence of polarization is small. Higher frequencies are used to measure high conductivities. Typically, the frequency is adjusted automatically during the measurement process, taking into account the obtained conductivity values of the solution. Modern digital two-electrode conductivity meters typically use complex AC current waveforms and temperature compensation. They are calibrated at the factory, but recalibration is often required during operation, since the constant of the measuring cell (sensor) changes over time. For example, it can change when the sensors become dirty or when the electrodes undergo physical and chemical changes.

In a traditional two-electrode conductivity meter (this is the one we will use in our experiment), an alternating voltage is applied between two electrodes and the current flowing between the electrodes is measured. This simple method has one drawback - not only the resistance of the solution is measured, but also the resistance caused by the polarization of the electrodes. To minimize the influence of polarization, a four-electrode sensor design is used, as well as coating the electrodes with platinum black.

General mineralization

Electrical conductivity measuring devices are often used to determine total mineralization or solids content(eng. total dissolved solids, TDS). It is a measure of the total amount of organic and inorganic substances contained in a liquid in various forms: ionized, molecular (dissolved), colloidal and in suspension (undissolved). Solutes include any inorganic salts. Mainly these are chlorides, bicarbonates and sulfates of calcium, potassium, magnesium, sodium, as well as some organic substances dissolved in water. To be classified as total mineralization, substances must be either dissolved or in the form of very fine particles that pass through filters with pore diameters of less than 2 micrometers. Substances that are constantly suspended in solution, but cannot pass through such a filter, are called suspended solids(eng. total suspended solids, TSS). Total suspended solids are commonly measured to determine water quality.

There are two methods for measuring solids content: gravimetric analysis, which is the most accurate method, and conductivity measurement. The first method is the most accurate, but requires a lot of time and laboratory equipment, since the water must be evaporated to obtain a dry residue. This is usually done at 180°C in laboratory conditions. After complete evaporation, the residue is weighed on a precision scale.

The second method is not as accurate as gravimetric analysis. However, it is very convenient, widespread and the fastest method, since it is a simple conductivity and temperature measurement carried out in a few seconds with an inexpensive measuring instrument. The method of measuring specific electrical conductivity can be used due to the fact that the specific conductivity of water directly depends on the amount of ionized substances dissolved in it. This method is especially convenient for monitoring the quality of drinking water or estimating the total number of ions in a solution.

The measured conductivity depends on the temperature of the solution. That is, the higher the temperature, the higher the conductivity, since ions in a solution move faster as the temperature rises. To obtain temperature-independent measurements, the concept of a standard (reference) temperature is used to which the measurement results are reduced. The reference temperature allows you to compare results obtained at different temperatures. Thus, a conductivity meter can measure actual conductivity and then use a correction function that will automatically adjust the result to a reference temperature of 20 or 25°C. If very high accuracy is required, the sample can be placed in an incubator, then the meter can be calibrated at the same temperature that will be used in the measurements.

Most modern conductivity meters have a built-in temperature sensor, which is used for both temperature correction and temperature measurement. The most advanced instruments are capable of measuring and displaying measured values in units of conductivity, resistivity, salinity, total salinity and concentration. However, we note once again that all these devices measure only conductivity (resistance) and temperature. All physical quantities shown on the display are calculated by the device taking into account the measured temperature, which is used for automatic temperature compensation and bringing the measured values to a standard temperature.

Experiment: measuring total mineralization and conductivity

Finally, we will perform several experiments to measure conductivity using an inexpensive TDS-3 total mineralization meter (also called salinometer, salinometer, or conductivity meter). The price of the “unnamed” TDS-3 device on eBay including delivery at the time of writing is less than US$3.00. Exactly the same device, but with the manufacturer’s name, costs 10 times more. But this is for those who like to pay for the brand, although there is a very high probability that both devices will be produced at the same factory. TDS-3 carries out temperature compensation and for this purpose is equipped with a temperature sensor located next to the electrodes. Therefore, it can also be used as a thermometer. It should be noted once again that the device does not actually measure the mineralization itself, but the resistance between two wire electrodes and the temperature of the solution. It automatically calculates everything else using calibration factors.

A total mineralization meter can help you determine the solids content, for example when monitoring the quality of drinking water or determining the salinity of water in an aquarium or freshwater pond. It can also be used to monitor water quality in water filtration and purification systems to know when it is time to replace the filter or membrane. The instrument is factory calibrated with a 342 ppm (parts per million or mg/L) sodium chloride solution, NaCl. The measuring range of the device is 0–9990 ppm or mg/l. PPM - part per million, a dimensionless unit of measurement of relative values, equal to 1 10⁻⁶ of the base indicator. For example, a mass concentration of 5 mg/kg = 5 mg in 1,000,000 mg = 5 ppm or ppm. Just as a percentage is one hundredth, a ppm is one millionth. Percents and ppm are very similar in meaning. Parts per million, as opposed to percentages, are useful for indicating the concentration of very weak solutions.

The device measures the electrical conductivity between two electrodes (that is, the reciprocal of resistance), then converts the result into specific electrical conductivity (in English literature the abbreviation EC is often used) using the above conductivity formula, taking into account the sensor constant K, then performs another conversion by multiplying the resulting conductivity by a conversion factor of 500. The result is a total salinity value in parts per million (ppm). Read more about this below.

This total mineralization meter cannot be used to test the quality of water with high salt content. Examples of substances with a high salt content are some foods (regular soup with a normal salt content of 10 g/l) and sea water. The maximum concentration of sodium chloride that this device can measure is 9990 ppm or about 10 g/l. This is the typical concentration of salt in foods. This device also cannot measure the salinity of seawater, as it is usually 35 g/l or 35,000 ppm, which is much higher than the device can measure. If you attempt to measure such a high concentration, the instrument will display the error message Err.

The TDS-3 salinity meter measures specific conductivity and uses the so-called “500 scale” (or “NaCl scale”) for calibration and conversion to concentration. This means that to obtain the ppm concentration, the conductivity value in mS/cm is multiplied by 500. That is, for example, 1.0 mS/cm is multiplied by 500 to get 500 ppm. Different industries use different scales. For example, in hydroponics, three scales are used: 500, 640 and 700. The only difference between them is in use. The 700 scale is based on measuring the concentration of potassium chloride in a solution and the conversion of specific conductivity to concentration is performed as follows:

1.0 mS/cm x 700 gives 700 ppm

The 640 scale uses a conversion factor of 640 to convert mS to ppm:

1.0 mS/cm x 640 gives 640 ppm

In our experiment, we will first measure the total mineralization of distilled water. The salinity meter shows 0 ppm. The multimeter shows a resistance of 1.21 MOhm.

For the experiment, we will prepare a solution of sodium chloride NaCl with a concentration of 1000 ppm and measure the concentration using TDS-3. To prepare 100 ml of solution, we need to dissolve 100 mg of sodium chloride and add distilled water to 100 ml. Weigh 100 mg of sodium chloride and place it in a measuring cylinder, add a little distilled water and stir until the salt is completely dissolved. Then add water to the 100 ml mark and stir thoroughly again.

To experimentally determine conductivity, we used two electrodes made of the same material and with the same dimensions as the TDS-3 electrodes. The measured resistance was 2.5 KOhm.

Now that we know the resistance and ppm concentration of sodium chloride, we can approximately calculate the cell constant of the TDS-3 salinity meter using the formula above:

K = σ/G= 2 mS/cm x 2.5 kOhm = 5 cm⁻¹

This value of 5 cm⁻¹ is close to the calculated constant value of the TDS-3 measuring cell with the electrode dimensions indicated below (see figure).

D = 0.5 cm - distance between electrodes;
W = 0.14 cm - width of electrodes
L = 1.1 cm - length of electrodes

The TDS-3 sensor constant is K = D/A= 0.5/0.14x1.1 = 3.25 cm⁻¹. This is not much different from the value obtained above. Let us recall that the above formula allows only an approximate estimate of the sensor constant.

Do you find it difficult to translate units of measurement from one language to another? Colleagues are ready to help you. Post a question in TCTerms and within a few minutes you will receive an answer.

Distilled water- purified water, practically free of impurities and foreign inclusions. It is obtained by distillation in special apparatus - distillers.

Characteristics

Distilled water is standardized based on GOST 6709-72 “Distilled water”.

Physical

The specific electrical conductivity of distilled water is usually less than 5 µS/cm. The conductivity of deionized water can be less than 0.05 µS/cm.

Distilled water has pH =5.4-6.6

Peculiarities

Being very clean, in the absence of foreign mechanical inclusions, it can be overheated above the boiling point, or supercooled below the freezing point without undergoing a phase transition. The phase transition occurs intensively with the introduction of mechanical impurities or shaking.

Usage

Distilled water is used to adjust electrolyte density, safe battery operation, flushing the cooling system, diluting coolant concentrates and for other household needs. For example, to adjust the freezing temperature of non-freezing windshield washer fluid and for color photo printing.

Harm to human health

Constant consumption of distilled water causes irreparable harm to human health due to the creation of an imbalance of water-salt balance. Imbalance occurs when the pH - the pH value of human blood and distilled water - does not match.

The most important parameter of drinking water for health

pH - hydrogen indicator

pH is a hydrogen indicator (from the Latin words potentia hydrogeni - the strength of hydrogen) - a measure of activity (in the case of dilute solutions, reflects the concentration) of hydrogen ions in a solution, quantitatively expressing its acidity, calculated as a negative (reversed) decimal logarithm of the concentration of hydrogen ions, expressed in moles per liter: pH = -log. Those. pH is determined by the quantitative ratio of H+ and OH- ions in water, formed during the dissociation of water. (A mole is a unit of measurement for the amount of a substance.) In distilled water, pH When the concentrations of both types of ions in a solution are the same, the solution is said to be neutral. When an acid is added to water, the concentration of hydrogen ions increases, and the concentration of hydroxide ions correspondingly decreases; when a base is added, on the contrary, the content of hydroxide ions increases, and the concentration of hydrogen ions decreases. When > the solution is said to be acidic, and when > it is alkaline.
The body balances the pH of internal fluids, maintaining values at a certain level. The acid-base balance of the body is a certain ratio of acids and alkalis in it, which contributes to its normal functioning.
The acid-base balance depends on maintaining relatively constant proportions between intercellular and intracellular waters in the tissues of the body. If the acid-base balance of fluids in the body is not constantly maintained, normal functioning and preservation of life will be impossible.
Optimal pH of drinking water = 7.0 to 8.0.

According to Japanese researchers, drinking water with a pH above 7 increases the life expectancy of the population by 20-30%.

How to determine the quality of distilled water? How are indicators analyzed and monitored? The concept of distilled water and its characteristics. Basic chemical indicators of this liquid. Regulatory documents for monitoring the quality of such water. Properties of distilled water and its effect on the human body. Methods of quality control in home and laboratory conditions. The quality of distilled water is checked by the remaining impurities. Analysis and control of indicators is directly related to the composition of the source liquid, the method of producing the distillate, the serviceability of the distillation device, as well as the conditions in which such water is stored.

Concept and characteristics

Distilled water is a liquid purified from substances of inorganic and organic origin. This includes compounds of mineral salts, suspended substances, pathogenic microorganisms, decomposition products from various living organisms, etc. It is important to understand that not every liquid that has undergone the process of evaporation and settled into condensate can be considered a distillate.

Distilled liquid is used to treat people, so its composition and quality are very important. Human health depends on this. In this regard, the quality of distilled water is regulated by standards, namely GOST 6709-72. The main characteristics of distilled water are described in these documents.

Basic indicators for distilled water	Concentration in mg per dm³
Item name	Not > 5
Residues of impurities after evaporation	Not > 0.02
Number of elements of ammonium salts and ammonia particles	Not > 0.2
Proportion of nitrates	Not > 0.5
Residues of impurities after evaporation	Presence of sulfates
Chlorination level	Not > 0.05
Chlorination level	Presence of aluminum particles
Iron residues	Not > 0.8
Residues of impurities after evaporation	Proportion of calcium elements
Chlorination level	Presence of copper particles
Number of elements of ammonium salts and ammonia particles	Presence of lead
Not > 0.08	Concentration of reducing elements
5,4-6,6	Liquid acidity
5 x 10 to the -4th power	Specific electrical conductivity of the composition

Distilled water comes in various stages of purification depending on the purpose of the liquid. Analysis of a liquid allows you to very accurately determine the degree of its purification and the presence of various impurities in the composition. So, there is a pyrogen-free liquid, which is distinguished by the complete absence of pyrogenic elements in its composition. These elements include substances of organic origin, as well as various bacterial components. Moreover, these components are able to negatively affect a person, causing symptoms such as increased body temperature, metabolic disorders, changes in the circulatory system, and the like. That is why the distillate, which is intended for the manufacture of injection formulations, must be cleaned of pyrogenic substances.

Distillate properties

It is very important to monitor the effect of the distilled liquid on the human body. As we have already said, the distillate is most often used for human treatment. That is why every pharmacy should keep a log of distilled water analysis. However, despite the medicinal properties of such a liquid, its uncontrolled intake is contraindicated, since the composition can have a negative effect on the human body.

If you decide to use distilled water instead of regular drinking water, you risk causing serious harm to your health, namely:

The distillate is capable of very quickly removing chloride compounds from the human body, which will lead to a persistent deficiency of this microelement.
Such water can lead to disruption of the volumetric and quantitative balance between liquid volumes in the human body.
Distilled water does not quench your thirst well, so you will drink more.
This liquid causes frequent urination, which entails the loss of potassium, sodium and chloride compounds, and their lack in the body.
The concentration of hormones responsible for water-salt balance is disrupted.

Distilled water quality control

You can control the composition of this liquid in several ways:

At home, using compact devices specially designed for this purpose.
Control of the amount of organic matter in the composition of water capable of reducing potassium permanganate.
Method of monitoring by specific electrical conductivity.

Let's look at each verification method in more detail.

At home, you can check the quality of distilled water using several devices at once. So, to control the hardness of the distillate, a device popularly called a salinity meter (TDS meter) is used. According to GOST number 6702-72, the permissible concentration of salts in distilled water is 5 mg/l. The percentage of chloride content in such water is determined using a chlormeter. According to GOST, this indicator should be equal to 0.02 mg/l. The acidity of water is measured with a pH meter, which allows you to very accurately determine the acid-base balance of the liquid. The norm for this indicator should be in the range of 5.4-6.6 mg/l. The specific electrical conductivity of distilled water is measured with a conductivity meter. The indicator is considered within normal limits if the device shows a value of 500.

The second control method can only be carried out in laboratory conditions. Its essence is that if substances capable of reducing potassium permanganate in a concentration of more than 0.08 mg/dm³ are detected in distilled water, the water is considered to be of poor quality. In such a situation, it is necessary to re-distill it with the addition of the necessary solutions.

A fairly common method for assessing the quality of distilled water is to test it by specific electrical conductivity. A solution of excellent quality is indicated by an indicator of at least 2 µS/cm.

Do you need to evaluate the quality of distilled water, but don’t have the necessary equipment to conduct the assessment yourself? Then contact our laboratory, where you will undergo all the tests necessary to control the quality of the liquid. To order an analysis, you just need to contact us at the numbers provided. You can check the cost of our services with the manager when you call.

STATE STANDARD OF THE USSR UNION

DISTILLED WATER

TECHNICAL CONDITIONS

GOST 6709-72

IPC PUBLISHING HOUSE OF STANDARDS

STATE STANDARD OF THE USSR UNION

Date of introduction 01.01.74

This standard applies to distilled water obtained in distillation apparatuses and used for the analysis of chemical reagents and the preparation of reagent solutions. Distilled water is a clear, colorless, odorless liquid. Formula: H 2 O. Molecular mass (according to international atomic masses 1971) - 18.01.

1. TECHNICAL REQUIREMENTS

1.1. In terms of physical and chemical indicators, distilled water must meet the requirements and standards specified in the table.

Indicator name
1. Mass concentration of the residue after evaporation, mg/dm 3, no more
2. Mass concentration of ammonia and ammonium salts (NH 4), mg/dm 3, no more
3. Mass concentration of nitrates (KO 3), mg/dm 3, no more
4. Mass concentration of sulfates (SO 4), mg/dm 3, no more
5. Mass concentration of chlorides (C l), mg/dm 3, no more
6. Mass concentration of aluminum (A l), mg/dm 3, no more
7. Mass concentration of iron (Fe), mg/dm 3, no more
8. Mass concentration of calcium (Ca), mg/dm 3, no more
9. Mass concentration of copper (C u), mg/dm 3, no more
10. Mass concentration of lead (P b), %, no more
11. Mass concentration of zinc (Zn), mg/dm 3, no more
12. Mass concentration of substances that reduce CM n O 4 (O), mg/dm 3, no more
13. Water pH
14. Specific electrical conductivity at 20 °C, S/m, no more

(Changed edition, Amendment No. 2).

2. ACCEPTANCE RULES

2.1. Acceptance rules - according to GOST 3885. 2.2. The manufacturer is allowed to determine indicators from 1 to 12 periodically. The frequency of inspection is determined by the manufacturer. (Introduced additionally, Amendment No. 2).

3. METHODS OF ANALYSIS

3.1a. General instructions for carrying out the analysis are in accordance with GOST 27025. When weighing, use general-purpose laboratory scales of the types VLR-200 g and VLKT-500 g-M or VLE-200 g. It is allowed to use other measuring instruments with metrological characteristics and equipment with technical characteristics no worse , as well as reagents of quality not lower than those specified in this standard. 3.1. Samples are taken according to GOST 3885. The volume of the average sample must be at least 5 dm 3. 3.1a, 3.1. (Changed edition, Amendment No. 2). 3.2. distilled water according to this standard; checked according to clause 3.3; distilled water, not containing ammonia and ammonium salts; prepared as follows: 500 cm 3 of distilled water is placed in a round-bottom flask of a distillation device, 0.5 cm 3 of concentrated sulfuric acid is added, heated to a boil and 400 cm 3 of liquid is distilled off, discarding the first 100 cm 3 of distillate. Water that does not contain ammonia and ammonium salts is stored in a flask closed with a stopper with a “goose” containing a solution of sulfuric acid; sulfuric acid according to GOST 4204, concentrated and solution 1:3; sodium hydroxide, solution with a mass fraction of 20%, not containing ammonia; prepared according to GOST 4517; Nessler's reagent: prepared according to GOST 4517; solution containing NH 4; prepared according to GOST 4212; by appropriate dilution prepare a solution containing 0.001 mg/dm 3 NH 4 ; a distillation device consisting of a round-bottomed flask with a capacity of 1000 cm 3 refrigerator with a splash trap and a receiving flask; flat-bottomed test tube made of colorless glass with a ground stopper, diameter 20 mm and capacity 120 cm 3; pipette 4(5)-2-1(2) and 6(7)-2-5(10) according to GOST 29169; cylinder 1(3)-100 and 1-500 according to GOST 1770. (Changed edition, Amendment No. 1, 2). 3.5.2. Carrying out analysis 100 cm 3 of the analyzed water is placed in a cylinder in a test tube, 2.5 cm 3 of sodium hydroxide solution is added and mixed. Then add 1 cm 3 of Nessler's reagent and mix again. Water is considered to comply with the requirements of this standard if the color of the analyzed solution observed after 20 minutes along the axis of the test tube is not more intense than the color of the reference solution prepared simultaneously with the analyzed solution and containing in the same volume: 100 cm 3 of water not containing ammonia and ammonium salts, 0.002 mg NH 4, 2.5 cm 3 sodium hydroxide solution and 1 cm 3 Nessler's reagent. 3.6. Determination of mass concentration of nitrates 3.5.2, 3.6. (Changed edition, Amendment No. 2). 3.6.1. distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution(NaOH) = 0.l mol/dm 3 (0.1 N), prepared according to GOST 25794.1 without establishing an adjustment factor; sodium chloride according to GOST 4233, solution with a mass fraction of 0.25%; solution containing NO 3; prepared according to GOST 4212; a solution containing 0.01 mg/cm 3 NO 3 is prepared by appropriate dilution; flask Kn-1-50-14/23 THS or Kn-2-50-18 THS according to GOST 25336; pipettes 4(5)-2-1 and 6(7)-2-5(10, 25) according to GOST 29169-91; evaporation cup 2 according to GOST 9147 or cup 50 according to GOST 19908; cylinder 1(3)-25(50) according to GOST 1770. 3.6.2. Carrying out analysis 25 cm 3 of the analyzed water is placed with a pipette in a cup, 0.05 cm 3 of sodium hydroxide solution is added, mixed and evaporated to dryness according to paragraph 3.3. The cup is immediately removed from the bath, 1 cm 3 of sodium chloride solution, 0.5 cm 3 of indigo carmine solution are added to the dry residue, and 5 cm 3 of sulfuric acid is added carefully while stirring. After 15 minutes, the contents of the cup are transferred quantitatively into a conical flask, the cup is rinsed in two doses with 25 cm 3 of distilled water, adding it to the main solution, and the contents of the flask are mixed. Water is considered to comply with the requirements of this standard if the color of the analyzed solution is not weaker than the color of the reference solution prepared as follows: 0.5 cm 3 of a solution containing 0.005 mg NO 3, 0.05 cm 3 of sodium hydroxide solution are placed in an evaporation cup and evaporated to dryness in a water bath. The cup is immediately removed from the water bath; then the dry residue is processed in the same way simultaneously with the dry residue obtained after evaporation of the analyzed water, adding the same amounts of reagents in the same order. 3.6.1, 3.6.2. (Changed edition, Amendment No. 1, 2). 3.7. Determination of mass concentration of sulfates (Changed edition, Amendment No. 2). 3.7.1. Reagents, solutions and equipment: distilled water according to this standard, tested according to clause 3.3; barium chloride according to GOST 4108, solution with a mass fraction of 10%; hydrochloric acid according to GOST 3118, concentration solution distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution(HC1) = 1 mol/dm 3 (1 n.), prepared according to GOST 25794.1 without establishing a correction factor; solution containing SO 4 ; prepared according to GOST 4212 on the water being analyzed by appropriately diluting the main solution with the same water to obtain a solution with a SO 4 concentration of 0.01 mg/cm 3 ; Rectified technical ethyl alcohol according to GOST 18300; pipettes 4(5)-2-2 and 6(7)-2-5(10) according to GOST 29169; glass V-1-50 TS according to GOST 25336; cylinder 1(3)-50 according to GOST 1770. 3.7.2. Carrying out analysis 40 cm 3 of the analyzed water is placed in a cylinder in a glass (with a 10 cm 3 mark) and evaporated on an electric stove to the mark. Then cool, add slowly with stirring 2 cm 3 of ethyl alcohol, 1 cm 3 of hydrochloric acid solution and 3 cm 3 of barium chloride solution, previously filtered through an ash-free “blue ribbon” filter. Water is considered to comply with the requirements of this standard if the opalescence of the analyzed solution, observed against a dark background after 30 minutes, is not more intense than the opalescence of a reference solution prepared simultaneously with the analyzed solution and containing: 10 cm 3 of analyzed water containing 0.015 mg SO 4, 2 cm 3 ethyl alcohol, 1 cm 3 of hydrochloric acid solution and 3 cm 3 of barium chloride solution. 3.7.1, 3.7.2. (Changed edition, Amendment No. 1, 2). 3.8. Reagents, solutions and equipment: Determination of mass concentration of chlorides 3.8.1. Carrying out analysis 50 cm 3 of the analyzed water is placed in a cylinder in an evaporation cup, 0.1 cm 3 of sodium carbonate solution is added and evaporated to dryness according to clause 3.3. The residue is dissolved in 3 cm 3 of water; if the solution is cloudy, it is filtered through an ash-free “blue ribbon” filter, washed with a hot solution of nitric acid with a mass fraction of 1%, and transferred to a test tube. The cup is washed with 2 cm 3 of water, adding the washing water to the solution, adding 0.5 cm 3 of a solution of nitric acid with a mass fraction of 25% and 0.5 cm 3 of a solution of silver nitrate with stirring. Water is considered to comply with the requirements of this standard if the opalescence of the analyzed solution observed after 20 minutes against a dark background is not more intense than the opalescence of a reference solution prepared simultaneously with the analyzed solution and containing in the same volume: 0.001 mg Cl, 0.1 cm 3 sodium carbonate solution, 0.5 cm 3 solution of nitric acid with a mass fraction of 25% and 0.5 cm 3 solution of silver nitrate. 3.8.1, 3.8.2. (Changed edition, Amendment No. 1, 2). 3.9. Determination of the mass concentration of aluminum using stilbazo (Changed edition, Amendment No. 2). 3.9.1. Reagents, solutions and equipment: distilled water according to this standard, tested according to clause 3.3; ascorbic acid (vitamin C) solution with a mass fraction of 5%, freshly prepared; acetate buffer solution pH 5.4; prepared according to GOST 4919.2; hydrochloric acid according to GOST 3118, concentration solution distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution(HC l) = 0.1 mol/dm 3 (0.1 n.); prepared according to GOST 25794.1 without establishing an adjustment factor; solution containing A l; prepared according to GOST 4212; a solution containing 0.001 mg/cm 3 A l is prepared by appropriate dilution; stilbazo, solution with a mass fraction of 0.02%; good for two months; pipettes 4(5)-2-1(2) and 6(7)-2-5(10) according to GOST 29169; test tube P4-15-14/23 HS according to GOST 25336; evaporation cup No. 2 according to GOST 9147 or cup 40(50) according to GOST 19908; cylinder 1(3)-25(50) according to GOST 1770. 3.9.2. Carrying out analysis 20 cm 3 of the analyzed water is placed in a cylinder in an evaporation cup and evaporated to dryness according to clause 3.3. 0.25 cm 3 of hydrochloric acid solution is added to the residue, 2.25 cm 3 of water is quantitatively transferred into a test tube, and 0.15 cm 3 of ascorbic acid solution, 0.5 cm 3 of stilbazo solution and 5 cm 3 of acetate buffer solution are added with stirring. Water is considered to comply with the requirements of this standard if the color of the analyzed solution after 10 minutes is not more intense than the color of the reference solution prepared simultaneously with the analyzed solution and containing in the same volume: 0.001 mg Al, 0.25 cm 3 hydrochloric acid solution, 0.15 cm 3 solutions of ascorbic acid, 0.5 cm 3 stilbazo solution and 5 cm 3 buffer solution. 3.9.1, 3.9.2. (Changed edition, Amendment No. 1, 2). 3.9a. Determination of mass concentration of aluminum using xylenol orange 3.9a.1. Reagents, solutions and equipment: distilled water according to this standard, tested according to clause 3.3; acetate buffer solution pH 3.4; prepared according to GOST 4919.2; hydrochloric acid according to GOST 3118, chemical grade, concentration solution distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution(HC l) = 0.1 mol/dm 3 (0.1 n.); prepared according to GOST 25794.1 without establishing an adjustment factor; xylenol orange, solution with a mass fraction of 0.1%; prepared according to GOST 4919.1; solution containing A l; prepared according to GOST 4212; a solution containing 0.001 mg/cm 3 A l is prepared by appropriate dilution; flask Kn-1-50-14/23 THS or Kn-2-50-18 THS according to GOST 25336; pipettes 4(5)-2-1 and 6(7)-2-5(10) according to GOST 29169; evaporation cup No. 3 according to GOST 9147 or cup 100 according to GOST 19908; cylinder 1(3)-100 according to GOST 1770. 3.9a.2. Carrying out analysis 60 cm 3 of the analyzed water is placed in a cylinder in an evaporation cup and evaporated to dryness according to clause 3.3. The residue is dissolved in 0.25 cm 3 of hydrochloric acid solution, 2 cm 3 of water and quantitatively transferred 8 cm 3 of water into a conical flask. Then 10 cm 3 of acetate buffer solution and 1 cm 3 of xylenol orange solution are added to the solution, the flask is placed in a water bath (80 °C) for 5 minutes and cooled. Water is considered to comply with the requirements of this standard if the pinkish-orange color of the pink tint observed in transmitted light against the background of milky glass is no more intense than the color of the reference solution prepared simultaneously with the test solution and containing 0.003 mg Al, 0.25 cm in the same volume of water 3 solutions of hydrochloric acid, 10 cm 3 of acetate buffer solution and 1 cm 3 of xylenol orange solution. 3.9a. - 3.9a.2. (Changed edition, Amendment No. 1, 2). 3.10. Reagents, solutions and equipment: Determination of mass concentration of iron (Changed edition, Amendment No. 2). 3.10.1. Carrying out analysis 40 cm 3 of the analyzed water is placed in a cylinder in a test tube, 0.5 cm 3 of sulfuric acid solution, 1 cm 3 of ammonium persulfate solution, 3 cm 3 of ammonium thiocyanate solution are added, mixed, 3.7 cm 3 of isoamyl alcohol is added, thoroughly mixed and kept until stratification of the solution. Water is considered to comply with the requirements of this standard if the observed color of the alcohol layer of the analyzed solution is not more intense than the color of the alcohol layer of the reference solution prepared simultaneously with the analyzed solution in the same way and containing: 20 cm 3 of the analyzed water, 0.001 mg of Fe, 0.25 cm 3 of sulfuric solution acid, 1 cm 3 of ammonium persulfate solution, 1.5 cm 3 of ammonium thiocyanate solution and 3 cm 3 of isoamyl alcohol. 3.11. Reagents, solutions and equipment: Determination of mass concentration of calcium 3.10.2, 3.11. (Changed edition, Amendment No. 2). 3.11.1. distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution distilled water according to this standard, tested according to clause 3.3; hydrochloric acid according to GOST 3118, solution with a mass fraction of 10%; prepared according to GOST 4517; murexide (ammonium salt of purple acid), solution with a mass fraction of 0.05%; good for two days; sodium hydroxide according to GOST 4328, concentration solution Carrying out analysis(NaOH) = 1 mol/dm 3 (1 N), prepared according to GOST 25794.1 without establishing a correction factor; solution containing Ca; prepared according to GOST 4212; a solution containing 0.01 mg/cm 3 Ca is prepared by appropriate dilution; test tubes P4-15-14/23 HS according to GOST 25336; pipettes 4(5)-2-1 and 6(7)-2-5(10) according to GOST 29169; evaporation cup 1 according to GOST 9147 or cup 20 according to GOST 19908; cylinder 1(3)-25(50) according to GOST 1770. 3.11.2. Reagents, solutions and equipment: distilled water according to this standard, tested according to clause 3.3; sodium N, N-diethyldithiocarbamate 3-water according to GOST 8864, solution with a mass fraction of 0.1%; freshly prepared; hydrochloric acid according to GOST 3118, solution with a mass fraction of 25%; prepared according to GOST 4517; solution containing Cu; prepared according to GOST 4212; a solution containing 0.001 mg/cm 3 Cu is prepared by appropriate dilution; isoamyl alcohol according to GOST 5830; a test tube made of colorless glass with a ground stopper with a capacity of 100 cm 3 and a diameter of 20 mm or a cylinder 2(4)-100 according to GOST 1770; pipette 4(5)-2-1(2) and 6(7)-2-5(10) according to GOST 29169; cylinder 1(3)-50(100) according to GOST 1770. (Changed edition, Amendment No. 1, 2). 3.12.2. Carrying out analysis 50 cm 3 of the analyzed water is placed in a cylinder in a test tube, 1 cm 3 of hydrochloric acid solution is added, stirred, 3.8 cm 3 of isoamyl alcohol and twice 1 cm 3 of a solution of 3-aqueous N,N-diethyldithiocarbamate sodium are added, stirring immediately after adding each portions of a solution of 3-aqueous N,N-sodium diethyldithiocarbamate for 1 min and incubated until separation. Water is considered to comply with the requirements of this standard if the observed color of the alcohol layer of the analyzed solution is not more intense than the color of the alcohol layer of the reference solution prepared simultaneously with the analyzed solution in the same way and containing: 25 cm 3 of the analyzed water, 0.0005 mg of Cu, 1 cm 3 of saline solution acid, 3 cm 3 isoamyl alcohol and 2 cm 3 solution of 3-aqueous N,N-diethyldithiocarbamate sodium. 3.13. Reagents, solutions and equipment: Determination of lead mass concentration 3.12.2, 3.13. (Changed edition, Amendment No. 2). 3.13.1. distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution distilled water according to this standard, tested according to clause 3.3; acetic acid according to GOST 61, chemically pure, solution with a mass fraction of 10%; potassium ferric sulfide 3-water according to GOST 4207, solution with a mass fraction of 1%, freshly prepared; sodium tetraborate 10-water according to GOST 4199, concentration solution Carrying out analysis 20 cm 3 of the analyzed water is placed in a cylinder in an evaporation cup and evaporated to dryness according to clause 3.3. The dry residue is treated with 1 cm 3 of acetic acid solution and again evaporated to dryness. Then the cup is cooled, the residue is moistened with 0.1 cm 3 of acetic acid solution, quantitatively transfer 3 cm 3 of water into a test tube, add 0.2 cm 3 of potassium ferric sulfide solution, 0.25 cm 3 of sulfarsazene solution, mix, add 2 cm 3 of tetraborate solution sodium and mix again. Water is considered to comply with the requirements of this standard if the color of the analyzed solution, observed along the axis of the test tube in transmitted light on a white background, will not be more intense than the color of the reference solution prepared simultaneously with the analyzed solution and containing in the same volume: 0.001 mg P b, 0.1 cm 3 solutions of acetic acid, 0.2 cm 3 solution of potassium ferrous sulfide, 0.25 cm 3 solution of sulfarsazen and 2 cm 3 solution of sodium tetraborate. 3.13.1, 3.13.2. (Changed edition, Amendment No. 1, 2). 3.14. Reagents, solutions and equipment: Determination of mass concentration of zinc (Changed edition, Amendment No. 2). 3.14.1. Carrying out analysis 5 cm 3 of the analyzed water is placed with a cylinder or pipette in an evaporation cup and evaporated to dryness according to clause 3.3. The cup is cooled, the dry residue is transferred quantitatively to 3 cm 3 of water into a test tube, and 0.8 cm 3 of tartaric acid solution, 0.2 cm 3 of citric acid solution, 0.8 cm 3 of ammonia solution and 0.5 cm 3 of sulfarsazene solution are added with stirring. . Water is considered to comply with the requirements of this standard if the color of the analyzed solution, observed along the axis of the test tube, in transmitted light on a white background is not more intense than the color of the standard solution prepared simultaneously with the analyzed solution and containing in the same volume: 0.001 mg Zn, 0.8 cm 3 tartaric acid solution, 0.2 cm 3 citric acid solution, 0.8 cm 3 ammonia solution and 0.5 cm 3 sulfarsazen solution. 3.15. Reagents, solutions and equipment: Determination of the mass concentration of substances that reduce potassium permanganate 3.14.2, 3.15. (Changed edition, Amendment No. 2). 3.15.1. distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution distilled water according to this standard, tested according to clause 3.3; potassium permanganate according to GOST 20490, concentration solution Carrying out analysis(1/5 KM n O 4) = 0.01 mol/dm 3 (0.01 N), freshly prepared, prepared according to GOST 25794.2; sulfuric acid according to GOST 4204, solution with a mass fraction of 20%, prepared according to GOST 4517; flask Kn-1-500-24/29 THS or Kn-2-500-34 THS according to GOST 25336; pipettes 4(5)-2-1 and 6(7)-2-5 according to GOST 29169; cylinder 1(3)-250 according to GOST 1770. 3.15.2. distilled water according to this standard, tested according to clause 3.3; indigo carmine; the solution is prepared according to GOST 10671.2; sulfuric acid according to GOST 4204, chemical grade; sodium hydroxide according to GOST 4328, chemical grade, concentration solution 250 cm 3 of the water being analyzed is placed in a cylinder in a flask, 2 cm 3 of sulfuric acid solution and 0.25 cm 3 of potassium permanganate solution are added and boiled for 3 minutes. Water is considered to comply with the requirements of this standard if, when observed in transmitted light against a white background, a pink color is noticeable in the analyzed solution when compared with an equal volume of the same water to which the above reagents have not been added. 1 cm 3 solution of potassium permanganate, concentration exactly

(KM n O 4) = 0.01 mol/dm 3 corresponds to 0.08 mg of oxygen. 3.15.1, 3.15.2. (Changed edition, Amendment No. 1, 2). 3.16. Determination of water pH is carried out using a universal EV-74 ion meter with a glass electrode at 20 °C. (Changed edition, Amendment No. 2). 3.17. Specific electrical conductivity is determined using a conductometer of any type at 20 °C.

4. STORAGE

4.1. Water is stored in hermetically sealed polyethylene and fluoroplastic bottles or other containers that ensure stable water quality. (Changed edition, Amendment No. 2).

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INFORMATION DATA

Initial value

Converted value

More about electrical conductivity

Introduction and Definitions

Specific conductivity is related to conductivity by the following formula:

G = σ(A/l)

The conductivity of metals, semiconductors and dielectrics is discussed in detail in the following articles of the Physical Quantity Converter website:, and Electrical conductivity. In this article we will discuss in more detail the specific conductivity of electrolytes, as well as methods and simple equipment for measuring it.

Specific electrical conductivity of electrolytes and its measurement

Theoretical sensor constant: left - K= 0.01 cm⁻¹, right - K= 1 cm⁻¹

To obtain the conductivity from the measured conductivity, the following formula is used:

σ = K ∙ G

σ - specific conductivity of the solution in S/cm;

K- sensor constant in cm⁻¹;

G- conductivity of the sensor in siemens.

The sensor constant is usually not calculated from its geometric dimensions, but is measured in a specific measuring device or in a specific measuring setup using a solution of known conductivity. This measured value is entered into the conductivity meter, which automatically calculates the conductivity from the measured conductivity or resistance values of the solution. Due to the fact that conductivity depends on the temperature of the solution, devices for measuring it often contain a temperature sensor that measures the temperature and provides automatic temperature compensation of the measurements, that is, normalizing the results to a standard temperature of 25 ° C.

General mineralization

Experiment: measuring total mineralization and conductivity

1.0 mS/cm x 700 gives 700 ppm

The 640 scale uses a conversion factor of 640 to convert mS to ppm:

1.0 mS/cm x 640 gives 640 ppm

In our experiment, we will first measure the total mineralization of distilled water. The salinity meter shows 0 ppm. The multimeter shows a resistance of 1.21 MOhm.

Measurement of resistance between two electrodes made of the same material and with the same dimensions as the TDS-3 electrodes; multimeter shows 2.5 kOhm

To experimentally determine conductivity, we used two electrodes made of the same material and with the same dimensions as the TDS-3 electrodes. The measured resistance was 2.5 KOhm.

Now that we know the resistance and ppm concentration of sodium chloride, we can approximately calculate the cell constant of the TDS-3 salinity meter using the formula above:

K = σ/G= 2 mS/cm x 2.5 kOhm = 5 cm⁻¹

This value of 5 cm⁻¹ is close to the calculated constant value of the TDS-3 measuring cell with the electrode dimensions indicated below (see figure).

D = 0.5 cm - distance between electrodes;
W = 0.14 cm - width of electrodes
L = 1.1 cm - length of electrodes

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 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.

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 .

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).

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).

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.

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 :

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.

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:

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

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.

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.

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.

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.

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. OBTAINING 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.

Guide to 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. Specific electrical conductivity (electrical conductivity)

This ability is directly related to the concentration of ions in water. Conducting ions come from dissolved salts and inorganic materials such as alkalis, chlorides, sulfides and carbonate compounds, etc. The more ions present, the higher the conductivity of water.

Ions conduct electricity due to their positive and negative charges. When substances dissolve in water, they split into positively charged (cationic) and negatively charged (anionic) particles. When solutes are broken down in water, the concentrations of each positive and negative charge remain equal. This means that although the conductivity of water increases with added ions, it remains electrically neutral

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.

Conductivity can be measured by applying an alternating electrical current (I) to two electrodes immersed in a solution and measuring the resulting voltage (V). During this process, cations migrate to the negative electrode, anions to the positive electrode and the solution acts as an electrical conductor. Voltage is used to measure water resistance, which is then converted to conductivity. Conductivity is the reciprocal of resistance and is measured in the amount of conductivity over a certain distance.

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). For very pure water, it is inconvenient to operate with the conductivity value, so the term resistivity, measured in Ohm/m (KOhm/cm or MOhm/cm), is more often used. So, for example, pThe conductivity of rivers can range from 50 to 1500 µS/cm, ddistilled water has a conductivity in the range from 0.5 to 5 µS/cm, ultrapure deionized water 10-18 MOhm/cm.

Conductivity in streams and rivers primarily depends on the geology of the area through which the water flows. Streams flowing through areas with granite rock tend to have lower conductivity because granite is composed of more inert materials that do not ionize (dissolve into ionic components) when washed in water. On the other hand, streams flowing through areas with clay soils tend to be more conductive due to the presence of materials that ionize when flushed in water. Groundwater inflows can have similar effects depending on where they flow through. Discharges to rivers can change conductivity depending on their composition. A faulty sewer system will increase conductivity due to the presence of chloride, phosphate and nitrate; an oil spill will reduce conductivity.

The conductivity of water must be accurately measured using a calibrated device - a conductivity meter. Conductivity is directly affected by the geometric properties of the electrodes; that is, conductivity is inversely proportional to the distance between the electrodes and proportional to the area of the electrodes. This geometric relationship is known as the cell constant. Constant cell and resistance measurement that must be checked and adjusted if necessary.

In addition to the geometric properties of the electrode in the device, and conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, electrical conductivity is reported as conductivity at 25 degrees Celsius (25 °C).Increasing the temperature of the solution will lead to a decrease in its viscosity and an increase in the mobility of ions in the solution. Increasing the temperature can also lead to an increase in the number of ions in solution due to the dissociation of molecules. Since the conductivity of a solution depends on these factors, increasing the temperature of the solution will lead to an increase in its conductivity. Knowing this dependencemany instruments automatically correct the actual reading to display the value that would theoretically be observed at a nominal temperature of 25°. This is typically done using a temperature sensor built into the conductivity sensor and a software algorithm built into the conductivity meter. However forLinear temperature compensation assumes that the temperature coefficient of variation has the same value for all measured temperatures. This assumption is incorrect; but for many measurements this does not make a significant contribution to the overall measurement uncertainty of the reported result.

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