The potassium sulfide compound is a colorless crystal. Its melting point is 948 ° C, with a specific gravity of 1.805 g / cm3 (the density is set at a standard temperature of 14 ° C). The crystals are highly soluble in aqueous solution and are highly hygroscopic. In addition, potassium sulfide is hydrolyzed, it is soluble in glycerol and ethanol. When interacting with them during the reactions, dihydrates and pentahydrates are formed, which are colorless crystals characterized by H0obr, respectively, -984.5 and -1880.0 kJ / mol.
The substance is very easy to oxidize in the open air, in this case K2S2O3 is formed, and SO2 is released during combustion. Potassium sulfide is obtained, the formula of which is K2S, by the interaction of K2CO3 with sulfur, and it is necessary to ensure the course of the reaction, excluding the influx of air. It is possible to obtain the substance by a reductive reaction, by exposing the K2SO4 salt to carbon.
Potassium sulfide is widely used as a necessary component in the composition of photosensitive emulsions and coatings in industry and photography. In chemical production, its use is based on the ability to act as a reagent in the separation of various metal sulfides. Application in the textile industry and leather industry consists in the inclusion of potassium sulfide in the composition of funds for the primary processing of leather.
In the form of KHS hydrosulfide or polysulfides, the substance is used in the sulfidation technologies of metal alloys, cast iron and steel. It is very widely used in the manufacture of drugs for the treatment of various skin diseases. Agricultural use of potassium sulfide - use as a pesticide.
As a rule, potassium sulfide is obtained in a rather simple way. For this, quicklime is mixed with sulfur and potash. Then this mixture is dissolved in water and boiled for several hours. As a result of this procedure, potassium polysulfide is formed. Then , calcium carbonate precipitate is removed from the resulting solution through a filter , and the solution itself is evaporated until it reaches a specific gravity of 1.25-1.30. Finally, a small amount of sulfur is still mixed into the solution, boiled again, and then drained after cooling.
The formation of potassium sulfide occurs quantitatively, however, for such a reaction, it is necessary to ensure very slow evaporation of NH3 vapor through a special tube, which must first be filled with potassium hydroxide. As a result of a correctly conducted reaction, a colorless ammonia solution and a white precipitate, which is potassium sulfide, should be obtained.
The resulting substance must be pumped out for a rather long time with a special oil pump, and then it should be calcined at a temperature of 400-500 ° C. As a rule, after this, the obtained crystals are crushed and purified with nitrogen in test tubes under vacuum.
The hydrolysis of potassium disulfide is a yellow powder; its formula is K2S2. The molecular weight of the substance is 142.327 amu At a temperature of 477 ° C, the disulfide begins to melt, and at 600 ° C it decomposes.
Potassium sulfide interacts with various substances. For example, by reaction with primary alkyl halides, symmetric dialkyl sulfides are obtained. Solutions of potassium sulfide are also mixed with solutions of various (primarily chromium-potassium and aluminum -potassium ) alum.
For medical purposes, high purity potassium sulfide is used. In this industry, it is represented by various coals, which are obtained from a mixture of the substance itself, its hydroxide and sulfur. Activation of medical coals occurs in special furnaces at a temperature of at least 800 - 900 ° C. Then there is a purification from sulfur compounds and washing off the chlorine ion with hydrochloric acid.