Potassium monosulphide

G. Taddei7 prepared potassium iodide by adding a dil. soln. of potassium monosulphide to an alcoholic soln. of iodine. In place pf potassium sulphide, J. von Liebig and C. Wittstock used barium sulphide, prepared by calcining sulphate with coke. According to R. Schindler, the products obtained by the sulphide process are contaminated with sulphur compounds. G. S. Serullas treated potassium antimoniate (prepared by calcining tartar emetic) with an alcoholic soln. of iodine as long as the soln. was decolorized. The filtered soln. was evaporated to the point of crystallization. 

Similar remarks apply to the f.p. curve of mixtures of potassium monosulphide and sulphur. 

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. 

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... 

H. Riesenfeld found the solubility of ammonia in soln. of sodium sulphide to be a linear function of the Na2S-conc. and they measured the ammonia press, of A-soln. of ammonia in sodium sulphide. With soln. containing 0 5, 1, and 1 5 mol. of sodium monosulphide, the respective press, of the ammonia were 15 18, 16 94, and 18 55 mm., when the press, of the ammonia in 2V-aq. soln. was 13 45 mm. According to W. P. Bloxam, potassium sulphide is stable at a low red heat and does not decompose when it is melted. P. Berthier stated that it is volatilized at high temp. When it is roasted in the air, potassium sulphide... 

In the analysis of brasses, Pelouze s volumetricul method may likewise be resorted to and, according to Calvert, with perfect accuracy. The brass is treated With an acid till perfect solution takes place, ammonia Is added In excess, and a standard solution of monosulphide of potassium introduced from a burette, whilst a black precipitate forms in the liquid, and until a white one begins to appear. The quantity of copper being found from the volume of liquid used in the precipitation, that of tho zmo may be taken as the difference. 

The monosulphide produced by this decomposition is also formed by the interaction of the potassium salt with cyanogen bromide ... 

Cyanogen monosulphide crystallises in rhomboidal crystals which partly sublime at 30° to 40° C. and melt at 60° C. It is soluble in water, alcohol, ether, carbon disulphide, chloroform, benzene and sulphuric acid. It is decomposed by hydrochloric acid. It precipitates iodine from potassium iodide. Alcoholic potash decomposes it into potassium cyanate and potassium thiocyanate ... 

Aurous sulphide, Au2S.—The pure sulphide can be prepared7 by saturation of a solution of potassium aurocyanide with hydrogen sulphide, and precipitation of the salt by acidifying the solution with hydrochloric acid. It is not produced by the action of hydrogen sulphide on a hot solution of auric chloride, as supposed by Berzelius.8 The moist substance has- a steel-grey colour when dried, it becomes brownish black. When freshly prepared, the sulphide dissolves in water to a colloidal solution, from which it is reprecipitated by addition of hydrochloric acid. The sulphide is unaffected by dilute acids, but is decomposed by powerful oxidizers such as aqua regia and chlorine. It is readily dissolved by solutions of polysulphides,0 and less readily by those of monosulphides. It also dissolves in a solution of potassium... 

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