338 Additional Experiments 



subject by the importanl controversy which has lately been 

 carried on between Mr. Murray and Mr. John Davy, re- 

 specting the nature of muriatic and oxymuriatic acids * ; 

 and I have been induced, by some hints which the discus- 

 sion has suggested, not only to repeat the principal experi- 

 ments described in my memoir, but to institute others with 

 the advantage of a more perfect apparatus than I then pos- 

 sessed, and of greater experience in the management of 

 these delicate processes. 



This repetition of my former labours has discovered to me 

 an instance in which I have failed in drawing the proper 

 conclusion from facts. In two comparative experiments 

 on the electrization of equal quantities of muriatic acid 

 gas, the one of which was dried bv muriate of lime, and 

 the other was in its natural state, I found a difference of 

 not more than one per cent, in the hydrogen evolved, re- 

 latively to the original bulk of the gasf. Yet, notvvithstand- 

 ing these results, I have expressed myself inclined to be- 

 lieve that some water is abstracted by that deliquescent salt ; 

 and this belief was confirmed several years afterwards, by 

 the event of an experiment in which muriatic acid gas, 

 dried by muriate of lime, gave only -j-V its bulk of hydro- 

 gen];, a proportion much below the usual average. The ques- 

 tion, 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 hydrogen gas is 

 obtained from muriatic acid gas, whether exposed or not to 

 muriate of lime ; and that its greatest amount does not 

 exceed -J^ or -j-V the original volume of the acid gas. 



In the paper last quoted §, I have also described an ex- 

 periment, in which sensible heat v/as 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 bv boiling, I was 

 not able to discover any increase of temperature, though a 

 very sensible air thermometer was inclosed in the vessel 

 containing the gas. The evolution of heat takes place, 



• Nicholson's Journal, vol. xxviii. and xxix. 



+ Phil. Trans, p. 191.— Phil. Mag. vol. vii. p. 213. % Phil. Trans, for 

 1809, p. 4.-3.3.— Phil. Mag. vol. xxiiv. p. 371. § P. 433, note.— Phil. 



Mag. vol. xxxiv. p. 371, note. 



only 



