254» EXPERIMENTS ON MOLYBDENA. 



and had a strong smell and taste of sulphuretted hidrogen. 

 At the end of four and twenty hours it became turbid, and 

 deposited a pretty considerable quantity of a yellowish 

 brown powder, which was separated and dried, when it he- 

 came of a brownish black. The filtered liquor was of a 

 I yellowish brown : when made to boil, sulphuretted hidrogen 



gas was evolved ; a larger quantity of powder was precipita- 

 ted; and it retained but a slight smell of sulphuretted hi- 

 drogen, which the addition of a few drops of muriatic acid 

 rendered stronger, at the same time producing a blue co- 

 lour. The precipitated powder, put into muriatic acid and 

 exposed to a moderate heat, comported itself like the resi- 

 duum of the preceding experiment; but boiling it ulti- 

 jnately produced a solution of a brownish yellow colour. 

 A little of this powder, being thrown into a redhot crucible, 

 burned immediately with a sulphurous flame, which soon 

 disappeared. 

 Puremolyb- This experiment shows, that pure molybdic acid is like- 

 djQ acid wi -wise capable of combining with hidrothian acid; but this 

 combine with , . ^ . . "^ , r- i f 



sulphuretted combmation is not as constant as that oi the preceding ex- 



Jiidrogen. periment, in which ammonia too is present. It proves the 

 variations, that the less limited disoxigenizing action of the 

 hidrothian acid must produce. Thus by dessication simply 

 it passes to the same state, to which the compound of the 

 preceding experiment is not to be brought but by a much 

 stronger heat ; and by the oxidation of a part of the hi- 

 drogen it forms a hidrothianate of sulphuret of molybdena, 

 that gives out in roasting a vivid sulphurous flame, which 

 the native sulphuret of molybdena does not, and is converted 

 into molybdic acid. 



It remains for me yet to examine the action of hidrothian 

 acid on molybdena in the same respects as in the 41st ex- 

 V periment, 



M 1 bdate of Exp. 46. Sulphuretted hidrogen was passed in the man- 

 ammonia d - ner already mentioned through a solution of a drachm of 



compos d and jjjoiy})^ate of ammonia in four ounces of water, which had 



reciissolvea oy •' 



sulphuricacid, been decomposed and redissolved by three drachms of rec- 



w"uh 'u?rhu- *'^^^ sulphuric acid. In two or three minutes the solution, 

 retted hidro- which was before like water, assumed a blue colour. Five 

 6^"' minutes after a light chocolate brown matter was deposited 



on 



