Potassium sulphide

The potassium sulphide compound iscrystals of the syngonic form 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 high hygroscopicity. In addition, potassium sulfide undergoes hydrolysis, is readily soluble in glycerol and ethanol. When reacting 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 toIn the open air, K2S2O3 is formed, and SO2 is released during combustion. 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 also possible to obtain the substance by a reducing reaction, acting on carbon with K2SO4.

Potassium sulfide is widely used as neededcomponent 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 polysulfidesthe 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 sulphide is an application as a pesticide.

As a rule, potassium sulphide is ratherin a simple way. To do this, mix the quicklime with sulfur and potash. Then this mixture is 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 occursquantitatively, however, for such a reaction flow, 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 solution of ammonia and a white precipitate should be obtained, which is potassium sulfide.

The obtained substance is necessary rathera long time to pump out a special oil pump, and then it should be calcined at a temperature of 400-500 ° C. Typically, after this, the crystals obtained are ground and cleaned with nitrogen in test tubes under vacuum.

The resulting potassium disulphideis a powder of yellow color, its formula is K2S2. The molecular weight of the substance is 142.327 amu. At 477 ° C, the disulfide begins to melt, and at 600 ° C it decomposes.

Potassium sulfide interacts with varioussubstances. 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 usedhigh 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 chloride ion is washed away with hydrochloric acid.