1819.] Muriatic Acid Gas. 31 
Another form of experiment occurred to me still more direct 
and simple, that of transmitting muriatic acid in its gaseous form 
over ignited metals. If water be obtained im this experiment, 
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 the metal 
decomposing the acid attracting its chlorine and liberating its 
hydrogen. And the experiment is further free from the only 
resource which remained to the advocates of that doctrine, in 
the case of water being obtained from muriate of ammonia, that 
it might be derived from the decomposition of the elements of 
ammonia, regarding it as an alkalicontaining oxygen. If water 
were really obtained from the combination of muriatic acid and 
ammoniacal gases, it would rather indicate, it was said, the 
decomposition of nitrogen than the existence of water as a con- 
stituent of muriatic acid. No weight, I believe, is due to such 
an assumption ; but if any importance were attached to it, it is 
precluded if water is obtained from the action of metals on 
muriatic acid gas. 
I have executed the experiment in several forms ; and in all 
with a more or less satisfactory result. 
One hundred grains of iron filings, clean and dry, were 
strewed for a length of five or six inches, in a glass tube, which 
was placed in an iron case across a small furnace, so as to admit 
of being raised to a red heat. This tube, of about two feet in 
length, was connected with a wide tube eight inches long, 
containing dry and warm muriate of lime ; and this was further 
connected at its other extremity, with a retort affording muriatic 
acid gas, from a mixture of supersulphate of potash and muriate 
of soda. The open extremity of the long tube, dipped by a 
shght curvature in quicksilver. On the iron being raised to 
ignition, and the transmission of the acid gas being conducted 
slowly, elastic fluid escaped from the extremity of the tube, which 
was found to be hydrogen; and though no trace of moisture 
appeared in the anterior part of the tube, it immediately con- 
densed in that part which was cold, beyond the iron filings. 
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 compo- 
sition of carbonate of lime. And I have found that dry magnesia dyes not absorb 
muriatie acid gas, though, with the aid of water, itforms acombination 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 alkalies, 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 com- 
bined 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 degree of 
heat which is necessary to produce it. 1 cannot, therefore, but consider the observ- 
ation alluded to as one altogether unfounded, and which ought not, ona mere 
speculation, to have been brought forward against a positive result. 
