SURROUNDING MEDIA ON VOLTAIC IGNITION. 
51 
In oxygen associated with coal gas the thermometer rose in five minutes — 
In oxygen. In coal gas. 
From 60° to 82°. From 60° to 76°. 
In hydrogen associated with coal gas the thermometer rose in five minutes — 
In hydrogen. In coal gas. 
From 60° to 77 °- From 60° to 82‘5°. 
From this it would appear that coal gas should be placed, as to its cooling effect on 
the ignited wire, between hydrogen and olefiant gas. 
On another day sulphuretted hydrogen associated respectively with oxygen and 
hydrogen was tried ; the wire in the sulphuretted hydrogen was at first ignited to a 
degree somewhat 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 gra- 
dually 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. 
From 60° to 79°. 
In sulphuretted hydrogen. 
From 60° to 8l°-5. 
This result would place sulphuretted hydrogen between hydrogen and coal gas ; 
but as the gas was rapidly decomposed, 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 further 
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 conducting power of the wire, as measured by the 
amount of gas in a voltameter included in the circuit. 
* Philosophical Transactions, 1847, p. 2. 
