256 EXPERIMENTS ON MOtYBDENA. 



On diffusing it in water the solution was of a fine deep 

 green. The molybdeaa however did not appear to be at- 

 tacked in any sensible degree. Forty grains of sulphur 

 were added, and the process as above was repeated three 

 times. The molybdena was still found to be but little al- 

 tered, and had lost oaly two grains. The solution being 

 decomposed by sulphuric acid, it yielded only a grayish 

 blue precipitate, the aspect of which was perfectly like 

 "What is called lac sufphuris, and contained a few flocks of a 

 yellowish gray, 

 lathedryway. j^^^ ^^^ j ^^^^ ^^^^ ^^^ drachms of alkaline lixivium, 

 thirty grains of sulphur, and ten grains of molybdena; 

 put the whole into a Hessian crucible ; evaporated to dry» 

 nefs; and left it in a red heat for a quarter of an hour. 

 The mass being diffused in eight ounces of water, and fil- 

 tered, the undissolved residuum weighed three grains. 

 The solution was of a fine yellowish red, and sulphuric acid 

 produced in it a blackish brown precipitate, which was in nO 

 respect altered by an excess of the same acid : the liquor 

 gave no sign of a blue appearance: and the precipitate^ af- 

 ter being separated, washed, and dried, was of a brownish 

 black, and weighed forty-five grains. 

 Precipitate ex- This precipitate was not altered by boiling in sulphuric 

 ^™'"'^ acid, and afterward wih muriatic: but when nitric acid 



was added to the muriatic, and it was boiled again, it was 

 decomposed and dissolved, with the exception of a little 

 sulphur. A solution of barytes indicated the presence of 

 sulphuric acid. Five grains of the precipitate, having beerx 

 heated redhot in a small glass, gave out about two grains of 

 sulphur. The residuum was speedily oxided by nitric 

 acid, but still a little sulphuric acid was found in the solu- 

 tion, which proves, that the action of the fire had not se- 

 pa:ated all the sulphur. From what has been said it fol- 

 lows, that the precipitate was composed of molybdena in 

 the metallic state, or approaching to it, of hidrothianat 0;f 

 sulphur, and of a slight excess of sulphur; while the pre- 

 cipitates in the 36th experiment were composed of oxide of 

 ii'olybdena combined solely with sulphuretted hidrogen, 05 

 at most with a little sulphur. This experiment having been 

 repeated with four times the quantity of molybdena, and 



the 



