Potassium sulphide

The potassium sulphide compound is a crystalline form of crystals that do not have a color. Its melting point is 948 ° C, with a specific density 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 have a high hygroscopicity. In addition, potassium sulfide is hydrolyzed, readily soluble in glycerol and ethanol. When interacting with them, dihydrates and pentahydrates are formed during the reactions, which are colorless crystals characterized by H0ob, respectively, -984.5 and -1880.0 kJ / mol.

The substance is very easily oxidizable in the open air, with the formation of K2S2O3, and with combustion, SO2 is released. A potassium sulphide is obtained, the formula of which is K2S, by the interaction of K2CO3 with sulfur, and it is necessary to ensure the reaction flow excluding air flow. It is possible to obtain the substance and by a reducing reaction, acting on carbon with K2SO4 salt.

Potassium sulfide is widely used as a necessary component in the composition of light-sensitive 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 sulphides. The application in the textile industry and leather production consists in the inclusion of potassium sulfide in the composition of the means for the primary treatment of the skins.

In the form of hydrosulfide KHS or polysulphides, the substance is used in the technologies of sulphidation 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 is an application as a pesticide.

As a rule, potassium sulphide is obtained in a rather simple way. To do this, mix the quicklime with sulfur and potash. This mixture is then dissolved in water and boiled for several hours. As a result of this procedure, potassium polysulphide is formed. Then a precipitate of calcium carbonate is removed from the resulting solution through the 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 added to the solution, boiled again, and after cooling, it is drained off.

The formation of potassium sulphide occurs quantitatively, but for this reaction it is necessary to ensure very slow evaporation of NH3 vapors through a special tube that must first be filled with potassium hydroxide. As a result of the correct reaction, a colorless ammonia solution and a white precipitate should be obtained, which is potassium sulfide.

The obtained substance must be pumped out for a long time with a special oil pump, and then it should be calcined at a temperature of 400-500 ° C. As a rule, after that, the obtained crystals are ground and purified with nitrogen in test tubes under vacuum.

The resulting potassium disulphide 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, when reacting with primary alkyl halides, symmetric dialkyl sulfides are obtained. Also, solutions of potassium sulfide are mixed with solutions of various alums (primarily chromic and alumokalic) alum.

For medical purposes, potassium sulfide is used for a high degree of purification. 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 takes place in special furnaces at a temperature not lower than 800 - 900 ° С. Then, the sulfur compounds are purified and the chlorine ion is washed with hydrochloric acid.