surrounding Media on Voltaic Ignition. 119 



In nitrogen. In carbonic acid. 



Exp. 1st. From 60° to 74°. 60° to 73°. 



2nd. 60° to 73°. 60° to 72°'5. 



The battery had in the last experiment a little decreased in 

 power; the oxygen and nitrogen both produced a less cooling 

 effect than the carbonic acid, but the oxygen came nearer to 

 it than the nitrogen, thus according with the previous experi- 

 ments. Upon the whole it would appear that oxygen pro- 

 duces a somewhat greater cooling effect on the ignited wire 

 than nitrogen, but these gases may, for the purposes of this 

 paper, be fairly regarded as equal. Atmospheric air produces 

 a similar effect to oxygen and nitrogen separately, though I 

 am inclined to think that a slight chemical change takes place 

 when atmospheric air is exposed to the ignited wire, and that 

 nitrous acid is formed; for if litmus paper be held over a vol- 

 taically ignited platinum wire in the air, a slight but very per- 

 ceptible tinge of red marks the portion of it immediately over 

 the wire. 



With the view of ascertaining whether the specific heat of 

 the surrounding media were the cause of the phaenomenon, I 

 proceeded to try the effect of the wire carrying a voltaic cur- 

 rent on different liquids; all things being disposed as in the 

 previous experiments, and 3 oz. of water being associated 

 respectively with the same quantity of the following liquids. 

 The thermometer rose in five minutes — 



In water, from 60°to 70°-3. In spirit of turpentine 60°to88°. i 



In water, from 60°to68°-5. In aether . . . . 60°to76°-l. 



I do not much rely on the last experiment, — the battery 

 was in more feeble action ; and though each of the above re- 

 sults is the mean of three experiments, yet the variations in 

 the results of the different experiments with aether being con- 

 siderable (while in the others they were very trifling), lead me 

 to place no great dependence on it. The rapidity of evapo- 

 ration and the readiness of ebullition of the aether require that 

 a larger quantity should be used ; but as this for the purpose 

 of comparison would have required all the experiments to be 

 repeated with different quantities of liquid, I have not thought 

 it worth while to go through the series a second time. It will 



