Potash is the informal name for a substance that chemists call potassium carbonate. This s alt has been known to people since ancient times, because it is contained in the ashes. Previously, this word was called precisely the dry residue after the evaporation of a solution of the 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 like this - K2CO3. It is an average s alt of potassium and carbonic acid. This means that the potash solution is not acidic or basic, it is neutral. For a long time it was confused with baking soda - NaHCO3.
History of discovery and study
Of course, we do not know for sure who was the first to receive potash, because it was known in ancient Greece and Rome. Then it was isolated from the ashes and used for washing. It is curious that for a long time it was confused with another substance - potassium bicarbonate. Familiar to us baking soda, potash - together they were called simply alkaline or alkaline s alts. They began to distinguish them in the XVIII-XIX centuries. For the first time this became known in 1759year, when Andreas Marggraf established that soda is a mineral alkali, while potash is vegetable. And in 1807, Humphry Davy established the chemical composition of each of these substances.
The first mention of potash production dates back to the 14th century. The largest of the enterprises were located in Germany and the Scandinavian countries. Potassium carbonate was used in soap factories, cloth industry, dyeing enterprises. In the 15th century, Russia also joined the competition. Prior to this, they did not know how to isolate potash from ash, but simply exported combustion products along with, for example, furs. The glass industry, both inside Russia and abroad, also needed this substance. Demand grew, and so did supply.
By the way, the very name "potash" is literally a hint of how it was obtained in ancient times. The fact is that in Latin it sounds like potassa, which in turn is a fusion of the words "ash" and "pot".
Chemical and physical properties
During the experiments with this substance, scientists received information about certain qualities inherent in it. It is now known that, under normal conditions, pure potash is a solid in the form of colorless crystals or a white powder. Its density is 2.43g/cm3. The melting point of potassium carbonate is 891 degrees Celsius. Highly hygroscopic.
This substance is not explosive or flammable. Causes irritation on contact with wet skin or mucous membranes. Thus,it is classified as a third hazard class.
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 removes organic matter, resulting in a potassium carbonate solution of this kind becomes completely colorless.
In addition, potash is also distinguished by varieties, there are only three. The quality of the final product depends on the content of impurities such as iron, aluminum, chlorides, sodium and sulfate s alts. Also, when assigning a grade, the mass fraction of the precipitate that precipitated in the solution and the loss on ignition are taken into account.
Production
Although the use 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 even make it at home.
First of all, you need to get at your disposal the ashes of vegetable origin. Then you need to dissolve it in a certain amount of hot water, stir well and wait a while. Next, you need to start evaporating the potash solution with a mixture of organic substances, which will cause 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 compared to the amount. So, of course, things are different on an industrial scale.
So, an aqueous solution of potassium carbonateinteracts with CO2 to form KHCO3. This, in turn, is heated, and water and carbon dioxide are released, the remainder is the original potash.
There are several more ways to obtain this substance, but the simplest and most effective are those described earlier.
Processing
As already mentioned, there are two types of potash - calcined and one and a half water. How is potassium carbonate processed to obtain one or another variety?
First of all, even their formulas differ. One and a half water looks like this: K2CO3+1, 5H2O, that is, it contains water initially. However, it is even more hygroscopic than normal. An anhydrous form can also be obtained from this form - it is enough to heat the powder to 130-160 degrees Celsius.
The calcined form is obtained by processing potassium carbonate obtained by evaporating a solution of ash in wooden vats. This stuff doesn't
is clean, so it has to be either calcined or calcined. After carrying out one of these procedures, the potassium carbonate powder turns white, and its solution is completely colorless. In this case, the substance does not contain water.
Use
For a long time and to this day, potassium carbonate in various forms is used in a huge number of industries and for a variety of purposes. For example, its excellent ability to purify up tostill used in the manufacture of liquid soap and other household chemicals.
In addition, potash is an antifreeze additive to mortars. As such, it allows mixtures to be more resistant to cold, making it possible to continue building even at fairly low temperatures. Its significant advantage over analogues is that it does not cause corrosion of structures, as well as the formation of efflorescence, which 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.
Potash is often a component of paints, and in the chemical industry it is used to absorb hydrogen sulfide from gas mixtures - it copes with this much better than soda. It also has a place in pharmaceuticals: potassium carbonate is involved in some reactions, and in some places it appears as a side result. Another area of application is fire fighting. It is with this substance that wooden structures are treated, thereby increasing their fire resistance.
Surprisingly, potash is also a dietary supplement. Its code is E501, so it belongs to class E. For a while it was used in confectionery, for example, in the manufacture of gingerbread. In light industry, this substance is also involved in the process of leather dressing.
Finally, there are high prospects for the use of potash in the manufacturenon-chlorine potash fertilizers. Ash has been used in this capacity for a long time, but in recent decades it has been supplanted by industrial feeds. Probably, in the near future, a method known for a long time and being the least harmful in comparison with the mineral fertilizers used now will be used on a large scale.
Other Features
Because 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 packing potassium carbonate. This is the only way to avoid unwanted ingress of water into this substance.
Also, surprisingly, despite its excellent reaction with H2O, potassium carbonate is completely insoluble in acetone and ethanol.
