VOLTAIC IGNITION. 339 



sulphuretted hydrogen was at first ignited to a degree some- 

 what inferior to that in oxygen, but the gas was rapidly 

 decomposed ; sulphur being deposited on the interior of the 

 vessel and the intensity of ignition gradually decreased, so as 

 ultimately to be scarcely superior to the ignition in hydrogen ; 

 indeed the gas by this time had become nearly pure hydrogen. 

 The following were the effects on the thermometer in five 

 minutes, all being arranged as before : 



In oxygen. In sulphuretted hydrogen. 



From 60 to 86. From 60 to 76. 



In hydrogen. In sulphuretted hydrogen. 



From 60 to 79. From 60 to 81-5. 



This result would place sulphuretted hydrogen between 

 hydrogen and coal gas ; but as the gas was rapidly decom- 

 posed, the greater part of the experiment was made with 

 hydrogen containing small quantities of sulphur combined, 

 and not with sulphuretted hydrogen. I therefore think that 

 proto-sulphuret of hydrogen, or the gas which consists of 

 equivalent ratios of the two elements, would be much farther 

 removed from pure hydrogen ; probably it would be about 

 equal in its cooling effect to carbonic acid or carbonic oxide. 



In phosphuretted hydrogen the platinum wire is destroyed 

 by combining with the phosphorus the instant it reaches 

 ignition, so that its relation to the other gases could not be 

 ascertained. 



Protoxide and deutoxide of nitrogen are, as I have 

 observed in the Bakerian Lecture, decomposed by the ignited 

 wire ; they, as well as atmospheric air, are, as nearly as may 

 be, equal in their effect to their elements separately. 



In the vapour of ether the ignited wire is extinguished 

 nearly as completely as in hydrogen; I have not yet tried its 

 comparative effect, but should judge it to be nearly the same 

 as coal gas or olefiant gas. 



In my former experiments* the following was the order of 

 the gases, testing the intensity of ignition by the inverse con- 



* Phil. Trans., 1847, p. 2. 



7. 2 



