Potassium thiomolybdates

Potassium Thiomolybdate, K2M0S4, is prepared, according to Berzelius loc. cit.), by gradually heating to bright redness a mixture of molybdenum disulphide, potassium carbonate, sulphur, and a little powdered charcoal. The water solution of the cold black melt is dark red in colour, and on gentle evaporation yields erj stals which may be further purified by precipitation of their aqueous solution with alcohol. The substance is not entirely stable. ... 

Of thef/iio-aciV/scorrespondhisfto the sulphides of molyhdemmi, two have been prepared, namely, hexathiomolybdic acid, HMoS . and per-thiomolybdic acid, H MoSj. The former has been obtained by decomposition of the ammonium salt with hydrochloric acid the latter is precipitated as a reddish-brown powder on the addition of dilute acetic acid to a solution of its potassium salt, KHM0S5.-... 

Potassium Thiodimolybdate, K2M02S, is obtained as a dark grey substance on addition of a deficiency of mineral acid (preferably acetic acid) to an aqueous solution of the normal thiomolybdate and evaporation of the brown liquid. 

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