ON MURIATIC ACID GAS, &C, 295 



Another form of experiment occurred to me still more di- 

 rect and simple, that of transmitting muriatic acid in its gase- 

 ous form over ignited metals. If water be obtained in this ex- 

 periment, it is a result which would prove subversive of the 

 new doctrine ; for muriatic acid gas is held to be the real acid, 

 free from water, and the only change which can happen, is that 



of 



ter essential to the salt. I did not think it necessary to make any reply to this 

 observation, founded entirely, as it appeared to me, on a mistaken assumption. 

 But I may take this opportunity of remarking, that there is no necessary truth 

 in the supposition that the ammoniacal salts must contain water which they can- 

 not yield. When acids combine with bases, the water of the acid does not ne- 

 cessarily remain in the compound. On the contrary, it is capable of being dri- 

 ven off from the greater numberof them, by an elevated' temperature ; and there 

 is no principle on which it can be. inferred, that ammonia should in this respect 

 be different from other bases. That it is incapable, as the same chemist remarks, 

 {Annals, vol. vii. p. 434.) of combining with a dry acid, so as to form a neutral 

 compound, is of no weight ; for the same thing is true of other bases, which yet, 

 when combined with such an acid by the aid of water, allow this water to escape 

 from the combination. He himself observes, that well-burnt lime, free from 

 water, does not absorb dry carbonic acid gas, but absorbs it rapidly if aqueous 

 vapour be admitted, though water is not retained in the composition of carbo- 

 nate of lime. And I' have found, that dry magnesia does not absorb muriatic 

 acid gas, though with the aid of water it forms a combination from which the 

 water can be expelled by heat.. That ammoniacal salts exist without water, is 

 evident from the combination of carbonic acid gas and ammoniacal gas, being 

 effected with the greatest facility ; and the circumstance that this compound is 

 not neutral, is one not depending on the peculiarity of the ammonia, and its not 

 containing water, like other bases, but on that of the carbonic acid, which, with 

 all the alkalis, even where water is present, has a tendency to form compounds 

 with excess of base. The reason why the ammoniacal salts do not yield the 

 combined water of their acids so completely as that of other salts, is, that from 

 their volatility, or their susceptibility of decomposition, they do not bear that de- 

 gree of heat which is necessary to produce it. I cannot, therefore, but consider 

 the observation alluded to, as one altogether unfounded, and which ought not on 

 mere speculation to have been brought forward against a positive result. 



