Potassium hydroxide monosulphide

J. J. Berzelius melted sulphur with an excess of potassium hydroxide and found the product to be a mixture of the monosulphide and thiosulphate. J. Kircher passed hydrogen sulphide over coarsely powdered sodium hydroxide at 100°. M. J. Fordos and A. Gelis made sodium sulphide by heating sodium carbonate with sulphur to 275° the product is obviously a kind of soda-liver of sulphur. J. W. Kynaston melted sodium hydroxide With calcium sulphide and J. V. Esop, and C. Vincent treated a soln. of barium or other sulphide with sodium or potassium... 

Potassium monosulphide, KaS.—The sulphide can be formed by direct union of the elements,13 by reduction of potassium sulphate with hydrogen or charcoal, and by the interaction of aqueous solutions of potassium hydroxide and potassium hydrogen sulphide. It is also produced by the action of sulphur on a solution of excess of potassium in liquid ammonia.14 On evaporation of its aqueous solution in vacuum at low temperature, the pentahydrate16 crystallizes. A dihydrate and a dodecahydrate are also known.18 The anhydrous salt can be obtained... 

In properties potassium monosulphide resembles the sodium salt. The anhydrous substance forms small cubic octahedra, isomorphous with the monosulphide of rubidium, but not with that of caesium.1 At the laboratory temperature its density is 1-805.2 The heat of formation of the solid from its elements is 87-1 Cal.,3 and the heat of solution is 22-7 Cal. In dilute solution it has a strongly alkaline reaction, owing to almost complete hydrolysis to the hydroxide and primary sulphide. 

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