VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. j* 



water of crystallization, it becomes red-hot, and melts without being volatilized. 

 Lastly, M. Fourcroy mentions it in the following manner: " As it contains much 

 water of crystallization, it immediately liquifies by a very moderate heat; but by 

 degrees it becomes dry, in proportion as the water of crystallization is dissipated. 

 In this state it first becomes red-hot, and soon melts without being volatilized, ac- 

 cording to Bucquet; butM. Baume asserts that it is demi-volatile. In repeating this 

 experiment I have observed, that in fact a part of this salt is sublimed, but a portion 

 remains fixed in the vessel, and doubtless it is concerning this that Bucquet speaks*." 

 When so many eminent chemists concurred in nearly the same assertion, I was 

 not a little surprized to observe, in some experiments made for a very different pur- 

 pose, that the whole of the sulphate of ammonia was not only volatilized by heat 

 but also that the distillation of it was accompanied with some remarkable phe- 

 nomena. I therefore diluted some very pure concentrated sulphuric acid with an 

 equal quantity of distilled water, and having saturated it with ammonia, I gradu- 

 ally evaporated it till it became a concrete salt. 



Exper. 1 . I put 2 oz. of the salt into a glass retort, capable of containing 3 

 times the quantity, then fitted on a receiver without any luting, and placed the 

 retort in a small open furnace over some lighted charcoal. The salt in the retort 

 speedily liquified, and a small portion of water first came over ; this was succeeded 

 by a considerable quantity of alkaline gas, which continued to be produced during 

 15 or 20 minutes. On a sudden the vessels were filled with a thick white cloud, 

 which on close inspection appeared to be composed of very minute glittering 

 crystals. This cload quickly disappeared, and was followed by a great quantity of 

 sulphureous gas and water, the greatest part of which was condensed in the re- 

 ceiver; and the operation went on in this manner while any thing remained in the 

 retort. During the distillation the matter in the retort was always liquid; and 

 when the operation was finished, I found in the receiver a considerable quantity of 

 sulphureous acid, with some ammonia in solution; and in the neck of the retort 

 there was sublimed a portion of the undecomposed salt. From this experiment I 

 was in a great measure convinced, not only that the neutral salt was decomposed, 

 but that the ammonia was also in part resolved into its constituent principles. 



Exper. 2. That I might however remove any doubt respecting this matter, I 

 fitted a bent glass adopter to a retort, and to this added a double tubulated re- 

 ceiver, from which proceeded a bent tube, which passed under a glass jar filled 

 with water and inverted. The former experiment was now repeated with this ap- 

 paratus; and I had the satisfaction to observe, that when the sulphureous acid 

 began to be produced, a quantity of gas at the same time displaced the water in 

 the jar, and continued to pass into it till to the end of the operation. This gas 

 I afterwards examined, and found that it possessed all the properties of the 

 azotic gas-}-. 



* Elemens d'Hist. Nat. et de Chimie, torn. 2, p. 93. — Orig. 



+ This operation requires to be conducted with caution ; for at the moment when the white cloud 

 VOL. XVIII. D 



