Electrical conductivity of liquids (conductive meter)
Electrical conductivity Or Conductivity Water represents the ability of electricity to pass through water. In fact, pure water is not a conductor of electricity. Because ions in water transmit electricity, there is a relationship between electrical conductivity and the total concentration of solutes in water.
The unit of electrical conductivity of hair water is in centimeters (mho / cm). (The unit of electrical resistance is Ohm, and since electrical conductivity is the inverse of resistance, its unit is ohm). Hair per centimeter is a large number, so the unit μmho / cm is usually used, which is one million times smaller.
The electrical conductivity of pure water at 25 ° C is 0.056 μmho / cm. Μmho / cm is also called microsiemens.
In almost pure water the relationship between Electrical conductivity And the total solute error is as follows:
EC = 2 TDS
When the concentration of impurities in water increases, the ions have a negative effect on each other’s motion and the electrical conductivity of the solution will no longer have a linear relationship with the ion concentration. In fact, the relationship between TDS and EC is different for each water sample and depends on the concentration and type of impurities in the water. For many urban and natural waters, μDS / cm = 55.1 (mg / l) TDS.
The electrical conductivity of water affects the rate of water corrosion and the degree of ionization of water salts, as follows:
1- With increasing EC or TDS, the rate of water corrosion increases. In other words two blue samples that in terms of Oxygen and pH Under the same conditions, the one with more EC tends to corrode more.
2- With increasing EC, the degree of ionization of salts in water decreases.
One simple way to determine the concentration of solutes in water is to measure electrical conductivity. Distilled water or pure water is almost not a conductor of electricity, but if salt water is present in it, it conducts electricity, and the more solutes dissolved in the water, the higher the electrical conductivity; In other words, its electrical resistance decreases. Due to the role of temperature in the electrical conductivity of water, measurements should be modified relative to the standard temperature of 25 ° C. Electric conductivity increases by approximately 2% for each degree Celsius increase, which can be shown as follows:
The units of measurement of electrical conductivity in a metric system are:
– Mouse per centimeter, which is shown as EC.
-Mill mouse per centimeter, shown as 3-10 EC x.
– Micro mouse per centimeter, shown as 6-10 EC x.
hmhos / cm
mhos / cm = 1000 mmhos / cm = 1000000 hmhos / cm
In the international system (SI), the Siemens unit per meter (S / m) is used, the conversion of which can be written as follows:
Siemens / meter (S / m) = 10 mmohs / cm
dS / m = mmhos / cm
The electrical conductivity of rainwater varies from 2 to 100 microns per centimeter, and in surface and groundwater it starts at about 90 millimeters per centimeter and reaches several thousand micromoles. The electrical conductivity of the high seas is about 90,000 micromoles, which is several times that of the high seas in the salt lakes.
If anions and cations are expressed in milliequivalents per liter, all of them must be equal or slightly different. The higher the amount of water-soluble ions, the greater the difference in total. In any case, the difference should not be more than 30.
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