EXPERIMENTS ON MOLYBDENA. 2^7 



turn of the liquor, about half a line thick, was of a brown 

 yellow colour. Having boiled the mixture and evaporated 

 to dryness, diluted the; residuum iii half an ounce of wa- 

 ter, and shaken it slightly, I had a fine blue solution, and 

 but little of the metal appeared to be left unaltered. Thus 

 the metal had here been oxided at the expense of the arsenic 

 acid, and converted into blue oxide. 



E.vp. 35. Ten grains of molybdena, half a drachm of ^^o^P^O"* 

 phosphoric acid, and a drachm of water, were put into a 

 phial, which was stopped close, and left to stand twenty- 

 four hours. No effect was produced, and the mixture was 

 boiled to dryness. When the residuum was nearly dry, a 

 ♦apour exhaled, which had a little of the smell of phospho- 

 rus, accompanied with something like that of an alkaline 

 lixivium when boiling- down. The flame of lighted paper 

 held over it assumed a greenish yellow colour. The resi- 

 duum was heated red hot, but no stronger smell was given 

 out, that covild lead me to suppose the phosphoric acid had 

 acted on the molybdena; and in fact when the mass was 

 cooled and diffused in half an ounce of water, the greater 

 part of the metal remained at the bottom, without having 

 undergone any alteration. The supernatant liquor was of 

 a yellowish brown colour, had a strongly acid taste, and left 

 a metallic taste on the palate. A similar quantity of water 

 was evaporated from the metal several times, but T did not 

 observe the least change, and no blue oxide was formed, 

 A small quantity of this solution was evaporated to dryness, 

 and a grayish blue matter remained, which, on dissolving it 

 again^ to my great surprise assumed a yellowish brown co- 

 lour. Ammonia added to the solution gave it a dull colour, 

 without producing any precipitate : it was not till after the 

 expiration of four and twenty hours, that a few brown flocks 

 separated. 



Exp. 36. Having treated molybdena in the same man- Eoracic add. 

 Rer with boracic acid, at the end of a fesv hours the liquor 

 assumed a slight blueish tint, which did not increase after- 

 ward, even when evaporated and the residuum again dis- 

 solved. Thus it appears, that boracic acid has no action 

 pn molybdena, and was not the cause of the slight blue co« 

 lour observed. 



Vol. XX Aug. 1803- S I had 



