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V. On the Effect of surrounding Media on f^oltaic Ignition. 
By W. R. Grove, Esq., M.A., E.P.R.S. 
Received August 10, — Read December 14, 1848. 
In the Philosophical Magazine for December 1845, I pointed out a striking differ- 
ence between the heat generated in a platinum wire by a voltaic current, according 
as the wire is immersed in atmospheric air or in hydrogen gas, and in the Bakerian 
Lecture for 1847 1 have given some further experiments on this subject, in which the 
wire was ignited in atmospheres of various gases, while a voltameter enclosed in the 
circuit yielded an amount of gas in some inverse ratio to the heat developed in the 
wire. It was also shown, by a thermometer placed at a given distance, that the 
radiated heat was in a direct ratio with the visible heat. 
Although the phenomenon was apparently abnormal, there were many known phy- 
sical agencies by which it might possibly be explained, such as the different specific 
heats of the surrounding media, their different conducting powers for electricity, or 
the varying fluency or mobility of their particles which would carry off the heat by 
molecular currents with different degrees of rapidity. 
The investigation of these questions will form the subject of this paper. 
An apparatus was arranged, see fig. 1. Two glass tubes A and B, of 0‘3 inch 
internal diameter and 1‘5 inch length, were closed with corks at each extremity; 
through the corks the ends of copper wires penetrated, and joining these were coils 
of fine platinum ware, one-eightieth of an inch diameter and 3’7 inches long when 
uncoiled. Tube A was filled with oxygen, tube B with hydrogen, and the tubes thus 
prepared were immersed in two separate vessels, in all respects similar to each other, 
and containing each three ounces of water. A thermometer was placed in the water 
in each vessel ; the copper wires were connected, so as to form a continued circuit, 
with a nitric acid battery of eight cells, each plate exposing eight square inches of 
surface. Upon the circuit being completed the wire in the tube containing oxygen 
rose to a white heat, while that in the hydrogen was not visibly ignited ; the tempe- 
rature of the water, which at the commencement of the experiment was 60°Fahr. in 
each vessel, rose in five minutes in the water surrounding the tube of hydrogen from 
60° to 70°, and in that containing oxygen from 60° to 81°*. 
Before I enter into a further detail of experiments, I would remark upon the ex- 
traordinary character of this result. The same current or quantity of electricity 
* After the publication of the Bakerian Lecture, my experiment on the peculiar effect of hydrogen on the 
ignited wire was noticed in a paper by M, Matteucci, which though I had it in my hand shortly after its 
MDCCCXLIX. H 
