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 
ea. of 
il ae i a te 
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, ona 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 F 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 
aot 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, e 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 
eombined water of their acids so conipletely 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. 
Q 
Sapefi 
