Dr. Henry's Additional 'Experiments , &c. 239 
of which was dried by muriate of lime, and the other was in 
its natural state, I found a difference of not more than on e per 
cent, in the hydrogen evolved, relatively to the original bulk 
of the gas.* Yet, notwithstanding these results, I have ex- 
pressed myself inclined to believe that some water is abstracted 
by that deliquescent salt; and this belief was confirmed, seve- 
ral years afterwards, by the event of an experiment in which 
muriatic acid gas, dried by muriate of lime, gave only ~ its 
bulk of hydrogen, •f a proportion much below the usual ave- 
rage. The question, however, was too interesting to be left 
in any degree of uncertainty ; and I have, therefore, made 
several fresh experiments with the view to its decision. In 
the course of these I have found, that though differences in 
the results are produced by causes apparently trivial, some 
of which I shall afterwards point out, yet that under equal 
circumstances, precisely the same relative proportion of hy- 
drogene gas is obtained from muriatic acid gas, whether ex- 
posed or not to muriate of lime ; and that its greatest amount 
< does not exceed ^ or ~ the original volume of the acid gas. 
In the paper last quoted, J I have also described an experi- 
ment, in which sensible heat was evolved by bringing muriate 
of lime into contact with muriatic acid gas ; a fact which, if 
established, would go far to prove the existence of water in 
that gas. But on repeating the experiment with muriate of 
lime recently cooled from fusion, and over mercury carefully 
deprived of all moisture by boiling, I was not able to discover 
any increase of temperature, though a very sensible air ther- 
mometer was inclosed in the vessel containing the gas. The 
evolution of heat takes place, only when the muriate of lime 
* Page 191. f Phil. Trans. 1809, page 433. $ Page 433 note, 
1 i 2 
