202 — Experiments on Muriatic Acid Gas, 
not account for the water obtained by the action of the metals - 
on this salt, 
When it is proved, that no extrinsic water exists in muriatie 
acid gas, there remain apparently only two modes on which the 
production of water can be explained,—either, that the metal — 
may require Jess oxygen than is supposed in combining with the . 
acid, so that a portion of water will remain undecomposed, to 
be deposited; or, that the oxide attracts more real acid, so as 
to liberate a larger proportion of water. ‘The first of these sup- 
positions is improbable, from the consideration of the law which 
regulates the combination of metallic oxides with acids,—that 
the quantity of acid is proportional to the quantity of oxygen, so 
that if an oxide were formed in these cases, at a lower degree 
of oxidation, it would only combine with a proportionally smaller 
quantity of acid, and the quantity of water detached from the 
combination would be the same. 
No improbability is attached to the second supposition ; and 
it has even some support from the consideration, that many me- 
tallic saline compounds form with an excess of acid, and that 
it is difficult, with regard to a number of them, to procure them 
neutral. Metailic muriates, with excess of acid, seem in parti- 
cular to be established with facility. And although an excess of 
metal be present in the action exerted on muriatic acid gas, this 
may not prevent the formation of a super-muriate, more espe- 
cially as the excess is in the metallic form, and exerts no direct 
action, therefore, on the real acid. 
To ascertain if a super-muriate were formed in these cases, 
the product obtained from the action of the muriatic acid on the 
metal was raised to a heat as high as could be applied without 
volatilization, so that no loosely adhering acid might remain, and 
the air in the retort was repeatedly drawn out by a caoutchoue 
bottle. The solution from the residue both of iron and zine was 
very sensibly acid. Some fallacy however attends this, from the 
circumstance, that the liquid state is necessary to admit of the 
indieations of acidity, and in adding water to produce this, a 
ehange occurs in the state of combination, in.a number of the 
metallic muriates ; a super-muriate being formed, which remains 
in solution, and a sub-muriate being precipitated, so that the 
acidity of the entire compound cannot justly be inferred from 
that of the solution. I found, accordingly, that on adding wa- 
ter to the product from the action of the acid gas on zinc, this 
change occurs; a little of a white precipitate being thrown 
down, while the liquor remained acid. But. the fallacy can be 
obviated, by adding only as much water as produces fluidity, 
without subverting the combination. Portions, therefore, of the 
residue were exposed to a humid atmosphere, until, by deliques- 
cence, 
