256 Dr Davy on the ComUnations of 



heat, and other disturbing causes. From the trials which I have 

 made of its solubility, water appears to take up about 17 per 

 cent, of it, at 55°. When I have added more salt, even at this 

 temperature, a portion has disappeared, but not without the dis- 

 engagement of air-bubbles ; and, at a higher temperature, as 

 at 98**; and above that, the disengagement of gas has been co- 

 pious, indicating a decomposition of the salt, which is also denot- 

 ed by its acquiring an ammoniacal odour. So great is the ten- 

 dency of the bicarbonate to undergo change with water, that, 

 though I have just spoken of its solution, I am doubtful if a 

 true solution of it can be obtained, or if it can exist in the state 

 of aqueous solution. I have been led to entertain this doubt, by 

 finding it impossible to saturate a solution of the sesquicarbon- 

 ate, by passing carbonic acid gas into it in Nooth''s apparatus ; 

 however great was the quantity of carbonic acid gas introduced, 

 the solution continued alkaline ; none of the acid appeared to 

 be arrested, excepting that portion which was fixed in the bi- 

 carbonate, the bicarbonate itself becoming solid and crystalline 

 as it formed. And I have been strengthened in the doubt, by 

 my inability to preserve either a weak or a strong solution, made 

 with the neutral salt, for any time, without its becoming alkal- 

 escent ; even immediately after the solution of inodorous crys- 

 tals, test-paper has indicated an excess of alkali. Even on the 

 solid salt, the presence of moisture acts as a disturbing cause. 

 Crystals, when put by, though perfectly inodorous, and appar- 

 ently dry at the moment, soon acquire, in close vessels, a distinct 

 and even strong ammoniacal odour, accompanied by the separa- 

 tion of moisture, — part of the water of crystallization ; and this, 

 I have observed, even takes place immediately, after removal 

 out of an atmosphere of carbonic acid gas, where the salt had 

 been exposed to considerable pressure. How to explain the 

 change seems difficult ; at least, keeping in view the formation of 

 the salt, it seems, as it were, a kind of link between inorganic 

 and organic chemistry. The influence of water, however, ap- 

 pears to be certain, and the only way in which I have been able 

 to preserve the bicarbonate for any length of time, has been 

 by keeping it perfectly dry, and putting into the bottle with it 

 chloride of calcium wrapped in paper. 



