EXPERIMENTS ON MOLYBOfiNA. ^^Q 



precipitate when dried was of a chocolate colour, and 

 weighed 3-^ grains. This appeared to be a simple hidro- 

 thianat [hidrosulphuret] of molybdena: for when heated 

 with muriatic acid a small quantity of sulphuretted hidro- 

 gen gas is evolved, and when heated redhot in a crucible it 

 does not give out the blue flame of sulphur, but simply a 

 smell of sulphurous acid. On decomposing it with nitric 

 acid, it immediately gave out sulphuric acid, which was 

 gendered evident by barytes. 



Exp. 38. Twenty-five grains of sulphuret of molybdena Heated redhot 

 were put into a lixivium containing* a hundred grains of 

 caustic alkali, evaporated, and heated redhot for a quarter 

 of an hour. As soon as the alkaline mass began to flow, 

 the alkali acted so powerfully on the molybdena, that the 

 whole of the metal seemed to be fused by it. The mass had and fused. 

 assumed a cherry red, which soon passed to a deep crimson. 

 The water in which this was difi'used acquired a deep green Part dissolved. 

 colour, which it lost in a few hours by mere exposure to the 

 air, and bec&ine of a blackish gray. The residuum, after Residuum, 

 being v/ashed and dried, was of a light gray colour, and 

 weighed twenty grains. Its nature will soon appear. 



Sulphuric acid and muriatic acid diluted with water, and Solution ex- 

 added in excess to the solution that had passed the filter, 

 extricated fiom it sulphuretted' hidrogen gas, and occasioned 

 a precipitate similar to that of the preceding experiment, 

 A part of the molybdena formed with the free acid a 

 blue solution above the precipitate. Nitric acid occasioned 

 a similar precipitate : but the blue liquid, that contained It, 

 became greenish, and afterward of a reddish yellow, in con- 

 sequence of the progressive oxidation.^ 



The experiments related indicate, that the alkali (potash) Potashactsbut 

 ^erts but little action on molybdena in the dry way, and ^^"^^ °^^** 

 Still less in the wet. I thought, that, if the quantity of 

 sulphur were increased, the action might be more consider- 

 able, and accordingly I made the following experiment. ^ 



Exp. 39. I took ten grains of powdered molybdena. Treated with 

 which I put into half an ounce of an alkaline lixivium P°[^?^^ '^'^'^ 

 holding in solution twenty grains of sulphur. This I boiled 

 and evaporated almost to dryness twice. The matter, as in 

 the 38th experiment, was of a cherry red round the edge. 

 S 2 Or 



