Potassium tetrasulphide

Tricobalt Tetrasulphide, Co3S4, has been obtained in the crystalline form by heating solutions of potassium sulphide with cobalt chloride in sealed tubes to 160-180° C.1... 

The trisulphide, K2S3J is formed by the action of excess of sulphur on a solution of potassium in liquid ammonia.5 The tetrasulphide, K2S4, the most stable member of the series, can be prepared by heating a mixture of potassium carbonate and sulphur at 800° C. in a current of carbon dioxide,6 or by the action of hydrogen sulphide on the fused pentasulphide. It yields an octahydrate, a trihydrate, and a semihydrate. Its heat of formation from the elements is 116-6 Cal.7... 

The monosulphide and polysulphides are formed by burning the metals in sulphur vapour, by the action of sulphur on the metals dissolved in liquid ammonia, and by the action of the molten metals on sulphur dissolved in toluene. Hydrates or alcoholates and, in some cases, the anhydrous compounds may be prepared by dissolving sulphur in hot solutions of the hydrosulphides or monosulphides. Potassium, rubidium and caesium give all the sulphides where = 1, 2, 3, 4, 5, or 6 sodium only up to the pentasulphide, and lithium only those for which x = 1, 2 and 4 (Pearson and Robinson, 1931). All the metals form two polysulphides of relatively outstanding stability one is invariably the disulphide, and the other tetrasulphide in the case of lithium or sodium, and pentasulphide in the case of potassium, rubidium or caesium. The amount of water of crystallisation and the solubility decrease with increase in atomic number of the metal, the gradation being most marked between sodium and potassium. 

Antimony Tetrasulphide, SbjS. —This was obtained by Berzelius by passing hydrogen sulphide gas into a solution of the tetroxide. Rose was able to obtain it from the decomposition of an aqueous solution of the fusion-product of the trisulphide and bisulphato of potassium by tartaric acid. It is a reddish-yellow powder. 

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