What is the distilled water? The pure, distilled water is missing a lot of components. Compared to conventional water, for example, with river water, the distillate water is missing a whole range of dissolved salts and gases.
And to be more precise, there is no pure water in the nature, even though water is the most common compound on the Earth. This paradox is explained quite simply: everything that we call water is nothing more than aqueous solutions of various substances. Water is a perfect solvent, and this kills it – in a chemically pure form the water is nowhere to be found. Even the rainfall on its short way to the ground has time to dissolve the oxygen and carbon dioxide, mix with dust and smoke. The transparent raindrops contain up to 0.005% impurities.
In the rivers the impurities are more. In the average city river, the dry residue can be 0.0124 oz or 350 mg per liter. In the oceans, the salt concentration can be up to 4%, but in the underground brine – more than 20%.
With few exceptions, the ordinary water is not such a deficiency thing. But for the distillate water, indeed, there is a demand. It’s needed in scientific laboratories and in pharmacy, for car owners in content of different chemicals and cleaners, and in household for steam irons. Finally, without the distilled water, many technological processes in chemical production wouldn’t be possible. For example, only the technical needs for the production of one kilogram of PET plastic require up to 4.62 gallons or 17.5 liters of pure water.
This is the distillate of the highest quality, containing tiny amounts of impurities. However, sometimes the acceptable impurity level is up to 0.05%. However, this water also should be obtained.
Let’s look in the history of the distilled water
Distillation is one of the simplest processes. There are two operations of distillation – evaporation and condensation – the distillation unit requires three simple ones: the tank of the water to be distilled, refrigerator and collector of the water condensate.
By this scheme, the water distillers work in modern research laboratories, by the same scheme two hundred years ago Antoine Laurent Lavoisier distilled the water in his laboratory. In those days, the water was considered as an element, and Lavoisier tried to study its properties by multiple distillations. This work eventually led to two important discoveries. First, it turned out that the “clean” rain water is heavier than the distillate water obtained from the water of Seine. Second, Lavoisier found out that the water is not an element, but the compound consisting of hydrogen and oxygen.
In the XIX century, the German physicist Friedrich Kohlrausch, who worked with extremely pure water, offered a very convenient criterion of its purity. Kohlrausch believed that the electrical conductivity of the water is very low, but the dissolved impurities in it can increase it in tens, hundreds or thousands of times. He repeatedly (40 times) distilled the water in a well sealed unit, and then boiled for another 500 hours in a golden flask to release the water from the dissolved gases and first of all from the carbon dioxide.
After this water treatment, the conductivity of the water could not be reduced in any way. The minimum value at room temperature was 5.5 Micro S/m. For the comparison you can note that the conductivity of the water that is distilled only once, in the air is almost 20 times greater, but the conductivity of drinking water is 0.005 – 0.05 S/m or 1,000 to 10,000 times better. The method of measuring the water electrical conductivity, which was used by Kohlrausch, has remained almost unchanged to this day.
