Thiotungstates preparation

Tungsten trisulfide [12125-19-8], WS3, is a chocolate-brown powder, slighdy soluble in cold water, but readily forming a colloidal solution in hot water. It is prepared by treating an alkah-metal thiotungstate with HC1 (52). Tungsten trisulfide is soluble in alkali carbonates and hydroxides. 

Normal ammonium thiotungstate, (NH4)3WS4, is prepared by the prolonged action of hydrogen sulphide on a dilute solution of ammonium... 

Xnmuil sodium ihiofungstate. XajWSj, is prepared by similar reactions to the above. The crystals are very hygroscopic, and are exceedingly soluble in water. The solutions of normal thiotungstates are not precipitated by zinc sulphate. Sodium tliiotungstate is soluble in alcohol. 

Thiotungstates of calcium, stroiifiurn, and barium ha% e been prepared by tlie action of hydrogen sulphide on suspensions of the corresponding tungstates, whereby yellow solutions were obtained from which the thiotungstates could be crystallised. 

The complexity of the oxide-sulfide transformation leads to some difficulties in sulfiding, for example, tungsten sulfide or other sulfide phases if in interaction with a nonoptimized support. In this respect, the use of thiosalts and more particularly thiomolybdates and thiotungstates represents an interesting alternative to the classical sulfidation of oxides. Ammonium thiomolybdate (NH)2MoS4 (ATM) was first synthesized by Kruss [53] in 1884. Later, Alonso et al. described an improved way of preparing ATM [54]. The synthesis of ammonivun thiotungstate (ATT)... 

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