]6 PHILOSOPHICAL TRANSACTIONS. [ANNO 1796. 



blue particles. The rest of the solution was then evaporated, and left a bright yel- 

 low mass at the bottom of the matrass. 



The undissolved residuum of the nitric solution was then boiled with lixivium of 

 pot-ash, which was afterwards saturated with muriatic acid, and became tinged with 

 blue when prussiate of pot-ash was added. The residuum was now a black powder, 

 which was edulcorated, and was immediately dissolved when nitric acid was poured 

 on it; at the same time nitrous fumes were emitted. The solution was transparent, 

 excepting that a few white particles were floating in it. It was then diluted, and 

 filtrated. Prussiate of pot- ash turned it to a brownish green, which afterwards be- 

 came brown. Lixivium of pot-ash precipitated a white flocculent matter; and 

 caustic ammonia, added to a third portion, precipitated a quantity of iron. 



As this precipitate had some remarkable properties, particularly in respect to the 

 difficulty with which it was decomposed, I have been induced to mention the ex- 

 periments made on it in a circumstantial manner. This precipitate appears from 

 these experiments to be principally composed of iron, and some molybdic acid, to- 

 gether with a small portion of alkali and sulphuric acid. The intimate union be- 

 tween the iron and molybdic acid is apparently the cause which impedes the decom- 

 position of this precipitate; but this can only be ascertained by future experiments 

 on molybdate of iron. 



I next examined the white precipitate which was deposited by the last evapora- 

 tions, and found that, when distilled with nitric acid, it was converted into the yel- 

 low molybdic acid; and I \va§ therefore convinced that this last portion of the white 

 precipitate was the same neutral salt which I obtained in several other operations, 

 and which has also been noticed by Scheele and Klaproth.* I now began to exa- 

 mine the blue solution b, which consisted of the sulphuric solution of molybdic 

 acid, saturated with ammonia; but that the experiments made on this may be 

 ' better understood, I shall first give an account of some experiments and observa- 

 tions which I have made on the sulphate of ammonia. 



Experiments and observations on the sulphate of ammonia. — This neutral salt, 

 which from Glauber, who first prepared it, was called the secret ammoniacal salt of 

 Glauber, or vitriolic ammonia, has been very little examined; neither has it been 

 applied to any useful purpose, though the inventor much recommended it in metal- 

 lurgical operations. It has been long known that the fixed alkalies, lime, and 

 barytes, when triturated with it, decompose it, by uniting with the acid. But the 

 effects of heat on it do not appear to have been sufficiently observed. Macquer 

 says, that it is demi-volatile, that it may be sublimed entire, and that it cannot be 

 decomposed in close vessels without some intermediate substance.-f- Baume makes 

 use of nearly the same expressions. J Bucquet says, that when it has lost the 



* Scheele observes, when molybdaena was detonated with nitre, and the mass afterwards dissolved in 

 water, and saturated with sulphuric, nitric, or muriatic acid, that a white precipitate was produced, 

 which was the acid of molybdaena combined with a portion of alkali. Essays, p. 231 and 240. — Orig. 



+ Diet, de Chimie, torn. 1, p. 111. — % Chimie Exp. et Raisonnee, torn. 1, p. S3\ — Orig. 



