VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 23 



effect.* Lastly, the white flocculent matter was boiled with nitric acid, and be- 

 came like the molybdic acid before it was dissolved. 



e. Nitric acid did not appear to have any effect on the molybdic acid when di- 

 gested with it. 



f. 2 oz. of lixivium of carbonate of pot-ash were poured on 10 grs. of the molyb- 

 dic acid. In a few minutes carbonic acid was gradually expelled, and as the molyb- 

 dic acid dissolved, a white flocculent matter was deposited. After it had stood some 

 hours, the clear liquor was decanted from the residuum. Prussiate of pot-ash did 

 not affect this solution. Some nitric acid was then dropped in, and produced a 

 reddish-brown precipitate, which was re-dissolved till the acid was in some excess. 



Muriate of tin, when added to a portion of the alkaline solution, was precipitated 

 white, but when some muriatic acid was dropped in, the precipitate became blue. 

 The white flocculent residuum, when treated with nitric acid as in the former 

 experiments, was converted into the yellow molybdic acid. Another portion of the 

 alkaline solution was evaporated to 4, and in proportion as the evaporation ad- 

 vanced, some of the white flocculent matter was precipitated, but I did not obtain 

 any crystals. 



g. 1 oz. of lixivium of carbonate of soda were poured on 10 grs. of molybdic acid. 

 In a few minutes carbonic acid was expelled, and when the molybdic acid was dis- 

 solved, a small quantity of white flocculent matter was precipitated. The clear solu- 

 tion was then poured from the residuum. Prussiate of pot-ash did not produce any 

 precipitate till the alkali was saturated with an acid. The effects of muriate of tin 

 were also the same as those mentioned in the former experiment. A part of the 

 solution was evaporated to half, and the next morning I found crystals, which, 

 though not very distinct, appeared to be in the form of four-sided tables with the 

 angles truncated. These crystals dissolved in water without leaving any residuum, 

 and when the solution was saturated with muriatic acid, the molybdic was precipi- 

 tated by prussiate of pot-ash, as in the former experiments. 



h. 1 oz. of carbonate of ammonia in solution were poured on 10 grs. of molybdic 

 acid, which appeared to be more readily dissolved than when the fixed alkalies were 

 employed. The solution appeared slightly turbid, but very little of it was precipi- 

 tated. The effects produced by prussiate of pot-ash and muriate of tin were the 

 same as in the preceding experiments. When a portion of the solution was distilled 

 to dryness, part of the molybdic acid remained unchanged, but another part was de- 

 prived of oxygen, and appeared in the form of»a dark grey powder. The remaining 

 part of the solution was considerably evaporated ; and the following day I found a 



* From the effects produced by muriate of tin on the molybdic aeid dissolved in water, in acids, and 

 in alkalies, it appears that it always tends to deprive the molybdic acid of a great part of its oxygen ; and 

 when water is the menstruum, the muriate of tin does this effectually ; but when the molybdic acid is 

 dissolved in sulphuric or muriatic acid, the muriate of tin has no effect, because, as I conceive, the 

 oxygen is supplied by the acid menstruum. This seems the more evident from the effects produced by 

 the muriate of tin when the excess of acid is saturated by an alkali. — Orig. 



