254 Dr. Faraday's Experimental Researches in Electricity. 



those which are directly due the action of the electric cur- 

 rent. 



746. The nature of the substances evolved will often lead 

 to a correct judgement of their primary or secondary charac- 

 ter, but is not sufficient alone to establish that point. Thus, 

 nitrogen is said to be attracted sometimes by the positive and 

 sometimes by the negative electrode, according to the bodies 

 with which it may be combined (554. 555.), and it is on such 

 occasions evidently viewed as a primary result* ; but I think 

 I shall show, that, when it appears at the positive electrode, 

 or rather at the anode, it is a secondary result (748. ). Thus, 

 also, Sir Humphry Davyf, and with him the great body of 

 chemical philosophers, (including myself,) have given the ap- 

 pearance of copper, lead, tin, silver, gold, &c, at the negative 

 electrode, when their aqueous solutions were acted upon by 

 the voltaic current, as proofs that the metals, as a class, were 

 attracted to that surface; thus assuming the metal in each 

 case to be a primary result. These however, I expect to 

 prove, are all secondary results; the mere consequence of 

 chemical action, and no proofs of the attraction or the law an- 

 nounced J. 



747. But when we take to our assistance the law of constant 

 electro-chemical action already proved with regard to water 

 (732.), and which I hope to extend satisfactorily to all bodies 

 (821.), and consider the quantities as well as the nature of the 

 substances set free, a generally accurate judgement of the 

 primary or secondary character of the results may be formed : 

 and this important point, so essential to the theory of electro- 

 decomposition, since it decides what are the particles directly 

 under the influence of the current, (distinguishing them from 

 such as are not affected,) and what are the results to be ex- 

 pected, may be established with such degree of certainty as 

 to remove innumerable ambiguities and doubtful considera- 

 tions from this branch of the science. 



748. Let us apply these principles to the case of ammonia, 

 and the supposed determination of nitrogen to one or the other 

 electrode (554. 555.). A pure strong solution of ammonia is 

 as bad a conductor, and therefore as little liable to electro- 



* Annates de Chimie, 1 804, torn. li. p. 172. 



+ Elements of Chemical Philosophy, pp. 144, 161. 



J It is remarkable that up to 1804 it was the received opinion that the 

 metals were reduced by the nascent hydrogen. At that date the general 

 opinion was reversed by Hisinger and Berzelius (Annates de Chimie, 1804, 

 torn. li. p. 174.), who stated that the metals were evolved directly by the 

 electricity ; in which opinion it appears, from that time, Davy coincided 

 (Philosophical Transactions, 1826, p. 388.); [or Phil. Mag. and Annals, 

 N.S. vol. i. p. 35.-Edit.] 



