Molybdenum trisulphide

Similar materials were used by Skeldon et al to produce a self-lubricating surface film on aluminium. They first produced a porous alumina film on the surface by anodizing, and then re-anodized in an electrolyte containing 0.01 M ammonium tetrathiomolybdate. They then found that the pores of the primary anodized film contained mainly amorphous molybdenum trisulphide, and this was converted by vacuum annealing to hexagonal molybdenum disulphide. The film gave a marked improvement in wear resistance. 

Clark, A.H., Evidence for the Geological Occurrence of Molybdenum Trisulphide, Nature Physical Science, 234, 177, (1971). 

This brownish powder, which is somewhat unstable in the air, ajid which is soluble in potassium sulpiride solution, is also obtained in small quantity by the interaction of molybdenum trisulphide and potassium sulphide. 

Apparent indicator constant 264, 267 Apparent stability constant 59 Aqua regia 111 Arc alternating current, 764 direct current, 763, 771 sensitivities of elements, (T), 766 Aromatic hydrocarbons analysis of binary mixtures, 715 Arsenates, D. of (ti) 357 Arsenic, D. of as silver arsenate, (ti) 357 as trisulphide, (g) 448 by iodine, (am) 634, (ti) 397 by molybdenum blue method, (s) 681 by potassium bromate, (ti) 406 by potassium iodate, (ti) 401 in presence of antimony, (s) 724 Arsenic(III) oxide as primary standard, 261... 

Ammonium sulphide) Barium sulphide Calcium sulphide Chromium (II) sulphide Copper (II) sulphide Diantimony trisulphide Dibismuth trisulphide Dicaesium selenide Dicerium trisulphide Digold trisulphide Europium (II) sulphide Germanium (II) sulphide Iron disulphide Iron (II) sulphide Manganese (II) sulphide Mercury (II) sulphide Molybdenum (IV) sulphide... 

The trisulphide M0S3 is precipitated when hydrogen sulphide is passed through weakly acid solutions of molybdates, or can be obtained by thermal decomposition of thiomolybdates, but it has also been identified in Chilean ores. It decomposes on heating above 1000°C to give free sulphur and molybdenum disulphide. 

Lavik et al ° reported up to 400% improvement in wear life, and lower friction at high or low temperature, when antimony trioxide was used in polyimide or polybenzothiazole-bonded films. Lower improvements, up to 270%, were obtained with antimony trisulphide, while Bartz reported that the addition of both graphite and antimony tetrasulphide (or antimony thio-antimonate Sb(SbS4)) gave a much greater improvement in the life of a polybutyltitanate-bonded molybdenum disulphide film than either of the additives separately. 

Wet Tests.— When hydrogen sulphide is passed through an acidified solution containing molybdenum, the trisulphide is thrown dowm. The precipitate dissolves in ammonium sulphide, and it is therefore in ordinary analysis separated with the Group IIb metals, namely, arsenic, antimony, tin, gold, and platinum. The last four metals may be precipitated by addition of metallic zinc, the arsenic expelled by evaporation, and, after taking to dryness with nitric acid, the molybdenum may be extracted from the residue with ammonia. The trisulphide may be reprecipitated directly by the addition of nitric acid to the solution in ammonium sulphide. A soluble sulphide added to a solution of ammonium molybdate gives a blue colour. 

The crystal structure of pentacarbonyl(tetraphosphorus trisulphide)-molybdenum has been determined.130 The structure shows an intact P4S3 cage molecule attached to a Mo(CO)s moiety through the apical phosphorus atom the i.r. spectrum of the compound suggests that the P4S3 molecule has strong phosphine-like interactions with the Mo(CO)5 system. 

Molybdenum compounds have attracted some interest recently. It was demonstrated that molybdenum dioxide (M0O2), trioxide (M0O3), and trisulphide (M0S3) reduced the flammability of plasticized PVC and polyesters and acted as a smoke suppressant. 

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