Pure water is a good cooler, does not contain free charge carriers. Under normal conditions, water is weakly dissociated and the concentration of protons (more precisely, hydronium ions H30 +) and hydroxyl ions HO- is 0.1 μmol / l. But since water is a good solvent, certain salts are almost always dissolved in it, that is, there are positive and negative ions in water. This allows water to conduct electricity. By the electrical conductivity of water, you can determine its purity.
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