25^ Dj* Davy on the Combinations of 



data before given, in connexion with the analysis of Carrara mar- 

 ble and muriate of ammonia, that this salt is composed of 



27.39 Ammonia, 

 64.58 Carbonic Acid, 

 18.03 Water; (considering the loss water) 

 or of 



17. Ammonia (1 porportion 17) 

 34.2 Carbonic Acid (I4 33) 



10.8 Water (I 9) 



an approximation, in regard to proportion, very close^ except- 

 ing in that of the water, the excess of which, it may be conceived, 

 is either hygrometrical, or, as is more hkely, only apparent from 

 inaccuracies committed with the experiments, and the data of 

 the calculations. 



The degree of solubility of the sesquicarbonate, and the 

 effects of heat on it, have been variously stated by authors. 

 I shall mention the results I have obtained in endeavouring to 

 determine these points with some care, and also some other pro- 

 perties belonging to the salt, not unworthy of notice, in relation 

 to the changes to which it is liable, depending on the operation 

 of complicated affinities. 



The quantity of sesquicarbonate which water is capable of 

 dissolving, varies, I find, very much with the temperature : — 

 Thus, 100 grains of water at 56"" Fahr.were saturated with about 

 25 grains of the salt ; at 62°, with about 30 grs. ; at 90°, with 

 about 37 grs. ; at 105% with about 41 grs. ; and at 120°, with 

 about 50 grs.* — the temperature at which the salt begins to be 

 decomposed, as is indicated by the disengagement of gas. 



It is commonly supposed, that a greater degree of heat than 

 the temperature last mentioned, is required to decompose this 

 salt ; but incorrectly. This degree is as near the true one as pos- 

 sible. At 118° the solution remains tranquil; at 120°, air- 

 bubbles are slowly disengaged ; and above this, the eff*ervescence 

 rapidly increases in violence, with every additional degree of heat. 



In mentioning the solubihty of the sesquicarbonate at differ- 

 ent temperatures, I have in every instance said about so much ; 

 for it is almost impossible to determine the quantity with abso- 



" The salt, in very fine powder, was added in small portions to the water 

 in a bottle with a glass stopple, shaken well after each addition, and the tem- 

 perature fixed by immersion in water. 



