CHEMICAL AFFINITY. 155 



also takes place, the nitric acid is deoxidised by the trans- 

 ferred hydrogen, and a current of electricity may be detected 

 in the metals or connecting metal by the application of a gal- 

 vanometer or any instrument appropriate for detecting such 

 effect. 



There are few, if any, chemical actions which cannot be 

 experimentally made to produce electricity : the oxidation of 

 metals, the burning of combustibles, the combination of oxy- 

 gen and hydrogen, &c., may all be made sources of elec- 

 tricity. The common mode in which the electricity of the 

 voltaic battery is generated is by the chemical action of water 

 upon zinc ; this action is increased by adding certain acids to 

 the water, which enable it to act more powerfully upon the 

 zinc, or in some cases act themselves upon it ; and one of the 

 most powerful chemical actions known that of nitric acid 

 upon oxidable metals is that which produces the most pow- 

 erful voltaic battery, a combination which I made known in 

 the year 1839 : indeed, we may safely say, that when the 

 chemical force is utilised, or not wasted, but all converted into 

 electrical force, the more powerful the chemical action, the 

 more powerful is the electrical action which results. 



If, instead of employing manufactured products or educts, 

 such as zinc and acids, we could realise as electricity the 

 whole of the chemical force which is active in the combustion 

 of cheap and abundant raw materials, such as coal, wood, fat, 

 &c., with air or water, we should obtain one of the greatest 

 practical desiderata, and have at our command a mechanical 

 power in every respect superior in its applicability to the 

 steam engine. 



I have shown that the flame of the common blowpipe gives 

 rise to a very marked electrical current, capable not only of 

 affecting the galvanometer, but of producing chemical decom- 

 position : two plates or coils of platinum are placed, the one 

 in the portion of the flame near the orifice of the jet, or at 

 the points where combustion commences, the other in the full 



