242 Prof. Connel on the Voltaic Decomposition 



dissolved body ; for the dissolved substance is often equally 

 capable, with water, in so far as respects composition and 

 atomic constitution, of yielding a definite proportion, whether 

 of oxygen or of hydrogen; and the non-appearance of one or 

 other of these elements at either pole is often equally expli- 

 cable on the idea of the dissolved substance not contain- 

 ing such element, and on that of its being derived from water, 

 and subsequently entering into union with the elements of the 

 dissolved substance. Many cases, however, occur, in which, 

 from peculiarity of atomic constitution, taken in conjunction 

 with the proportion of gases evolved at the poles, we can have 

 little hesitation in pronouncing in favour of a secondary ac- 

 tion. Such cases, I conceive, are those of nitric, sulphurous 

 and the organic acids, and of ammonia, as exemplified in Mr. 

 Faraday's experiments. 



Accordingly, although in such instances as these Mr. Fa- 

 raday decided with reason in favour of such r-^ir action, yet he 

 was so far from laying down as a genera' rule, that in all cases 

 of solution of acids, alkalies and other primary combinations 

 of elements, the dissolved body was never directly decom- 

 posed by galvanic agency, that he distinctly gave his opinion 

 hat the hydracids are directly decomposed *, and inclined to 

 the view also that the haloid salts were in the same situa- 

 tion. 



By adopting other methods, with the occasional aid of the 

 principle of the voltameter, I conceive that I have been en- 

 abled to extend the rule of secondary action to all cases of 

 aqueous solution of primary combinations of elementary 

 bodies. 



Tlie usual method followed, was to endeavour to separate 

 some one of the constituents of the dissolved body, on the 

 assumption that that body was directly decomposed, and to 

 exhibit it in a distinct shape. The solution, contained in a 

 small tube of the capacity of about one and a half drachm, was 

 connected with another tube of the same capacity filled with 

 distilled water, the connexion being made by a short and 

 thick bundle of asbestus previously well washed with dilute 

 acid and then with distilled water, with which latter fluid it 

 was still moist when the connexion was made, and the level of 

 the solution being a fraction of a line lower than that of the 

 distilled water. 



The water was then connected with the side of the battery, 

 to which the constituent of the dissolved substance would na- 

 turally pass if that substance suffered direct decomposition, 



* Ubi sup. §. 763-4. 



