surrounding Media on Voltaic Ignition. 117 



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 hy- 

 drogen containing small quantities of sulphur combined, and 

 not with sulphuretted hydrogen. 1 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 igni- 

 tion, so that its relation to the other gases could not be ascer- 

 tained. 



Protoxide and deutoxide of nitrogen are, as I have ob- 

 served 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 aether 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- 

 ducting power of the wire, as measured by the amount of gas 

 in a voltameter included in the circuit. 



Cubic inches of gas evolved in 

 Gases surrounding the wire. the voltameter per minute. 



Hydrogen 7*7 



Olefiant gas 7*0 



Carbonic oxide 66 



Carbonic acid 6'6 



Oxygen 6'5 



Nitrogen 6'4 



Assuming that in the present experiments the heat in the 

 water is a correct indication of the intensity of ignition in the 

 wire, the order is the same in both series of experiments. 



* Philosophical Transactions, 1847, p. 2. [Phil. Mag. S. 3. vol. xxxi. p. 21.] 



