Potash is ... The formula and application of potash

Potash is an unofficial name for a substance that chemists call potassium carbonate. This salt is known to people since ancient times, as it is contained in ashes. Previously, this word was called the dry residue after evaporation of the solution of combustion products of plants. So, what is now known about potash?

Formula

Another name for this substance is potassium carbonate. And its chemical formula is written as - K ₂ CO ₃ . It is an average salt of potassium and carbonic acid. This means that the solution of potash is not acidic or basic, it is neutral. For a long time he was confused with baking soda - NaHCO ₃ .

History of discovery and study

Of course, for certain we do not know who was the first to receive potash, because he was known in ancient Greece and Rome. Then it was separated from the ash and used for washing. It is curious that for a long time it was confused with another substance - potassium hydrogen carbonate. The food soda familiar to us, potash - together they were called simply alkaline or alkaline salts. Distinguish them began in the XVIII-XIX centuries. This was first known in 1759, when Andreas Marggrave found that soda is a mineral alkali, while potash is a vegetable alkali. And in 1807, Gemfri Davy established the chemical composition of each of these substances.

The first mention of the production of potash dates back to the 14th century. The largest enterprises were in Germany and the Scandinavian countries. Potassium carbonate was used in soap-makers, cloth industry, dyeing enterprises. In the 15th century, Russia joined in the competition. Prior to this, it was not possible to separate potash from ash, but simply exported combustion products along with, for example, furs. The glass industry both in Russia and abroad also needed this substance. The demand grew, and with it the supply also grew.

By the way, the very name "potash" - this is literally a hint of a way to get it in antiquity. The fact is that in Latin it sounds like a potassa, which in turn is a fusion of the words "ash" and "pot".

Chemical and physical properties

In the course of experiments with this substance, scientists received information about certain qualities inherent in it. To date, it is known that, under normal conditions, pure potash is a solid in the form of colorless crystals or white powder. Its density is 2.43 g / cm ³ . The melting point of potassium carbonate is 891 degrees Celsius. Has high hygroscopicity.

This substance is not explosive or fire-hazardous. If exposed to damp skin or mucous membranes, it causes irritation. Thus, he is referred to the third class of danger.

Varieties and forms

There are two types of potash: calcined and one-and-a-half-water. Unlike the second, the first form does not contain water - in the process of calcination, it Evaporates, and also organic substances are removed, as a result, a solution of potassium carbonate of this kind becomes completely colorless.

In addition, distinguish between potash and varieties, only three are distinguished. The quality of the final product depends on the content of such impurities as iron, aluminum, chlorides, sodium and sulfate salts. Also, when assigning a variety, the mass fraction of the precipitate precipitated in the solution and the loss on ignition are taken into account.

Extraction

Although the application of potash does not occur on such a huge scale as in the case of soda, it is still actively used by people. But first of all you need to get it. In small quantities, you can do it even at home.

First of all, it is necessary to get the ash of plant origin at your disposal. Then you need to dissolve it in some hot water, stirring well and waiting for a while. Next, you need to start evaporating the potash solution with a mixture of organic substances, which will cause the crystals to fall out. Of course, potassium carbonate, isolated in this way, will not be of high quality, and the effort spent is too great in comparison with the quantity. So, of course, on an industrial scale everything happens differently.

Thus, an aqueous solution of potassium carbonate reacts with CO ₂ , which results in the formation of KHCO ₃ . It, in turn, is heated, and water and carbon dioxide are released, in the remainder - the original potash.

There are several other ways to get this substance, but the simplest and most effective are those described earlier.

Treatment

As already mentioned, two types of potash are distinguished - calcined and one-and-a-half-water. How does the treatment of potassium carbonate take place to produce this or that variety?

First of all, even their formulas differ. The one-and-a-half-year-old looks like this: K ₂ CO ₃ + 1.5H ₂ O, that is, it contains water initially. Nevertheless, it is even more hygroscopic than normal. From this form, you can get and anhydrous form - it is enough to heat the powder to 130-160 degrees Celsius.

The calcined form is obtained by treating potassium carbonate obtained by evaporation of the ash solution in wooden vats. Such a substance is not Differs purity, so it must either be calcined or calcined. After carrying out one of these procedures, the powder of potassium carbonate is obtained in white, and its solution is completely colorless. In this case, the substance does not contain water.

Using

From ancient times to this day, potassium carbonate in different forms is used in a huge number of industries and with a variety of purposes. For example, its excellent purification ability is still used in the manufacture of liquid soap and other household chemicals.

In addition, potash - antifreeze additive to mortar. In this capacity, it allows the mixtures to be more resistant to cold, which makes it possible to continue construction even at rather low temperatures. Its significant advantage over analogues is that it does not cause corrosion of the structures, as well as the formation of highs that could Affect the strength of the structure.

Potassium carbonate is still used in the manufacture of crystal and glass for high-quality optics. There is no substitute for him in this matter. There are no analogues of this substance, for example, in the manufacture of refractory glass.

Often potash is a component of paints, also in the chemical industry it is used to absorb hydrogen sulphide from gas mixtures - with this, it copes much better than soda. There is also a place for him in pharmaceutics: potassium carbonate is involved in some reactions, and in some places appears as a by-product. Another area of application is firefighting. It is this substance that processes wooden structures, thereby increasing their fire resistance.

Surprisingly, potash is also a food additive. Its code is E501, so it belongs to class E. It was used for a while in confectionery, for example, when making gingerbread. In light industry, this substance is also involved in the process of manufacturing leathers.

Finally, there are high prospects for the use of potash in the production of chlorine-free potassium fertilizers. Ash in this capacity has been used for a long time, but in recent decades it has been supplanted by industrial dressings. Probably, in the near future a method, known long ago and being the least harmful in comparison with the mineral fertilizers used now, will be applied on a large scale.

Other Features

Since potash is an extremely hygroscopic substance, its packaging, storage and transportation take place under special conditions. As a rule, five-layer bags are used for filling potassium carbonate. This is the only way to prevent unwanted water from entering this substance.

In addition, surprisingly, despite the excellent reaction with H ₂ O, potassium carbonate is completely insoluble in acetone and ethanol.