166 Dr. Faraday's Experimental Researches in Electricity. 



decomposition as the one I have propounded ; for if it be ad- 

 mitted, as is generally the case, that the more directly bodies 

 are opposed to each other in their attractive forces, the more 

 powerfully do they combine, then the objection applies with 

 equal force to any of the theories of electrolyzation which 

 have been considered, and is an addition to those which 

 I have taken against them. 



675. Amongst powerful compounds which are not decom- 

 posed, boracic acid stands prominent (408.). Then again, 

 the iodide of sulphur, and the chlorides of sulphur, phos- 

 phorus, and carbon, are not decomposable under common 

 circumstances, though their elements are of a nature which 

 would lead to a contrary expectation. Chloride of antimony 

 (402. 690.), the hydro-carbons, acetic acid, ammonia, and 

 many other bodies undecomposable by the voltaic pile, would 

 seem to be formed by an affinity sufficiently strong to indicate 

 that the elements were so far contrasted in their nature as to 

 sanction the expectation that the pile would separate them, 

 especially as in some cases of mere solution (530. 544.), where 

 the affinity must by comparison be very weak, separation 

 takes place*. 



676. It must not be forgotten, however, that much of this 

 difficulty, and perhaps the whole, may depend upon the ab- 

 sence of conducting power, which, preventing the transmis- 

 sion of the current, prevents of course the effects due to it. 

 All known compounds being non-conductors when solid, but 

 conductors when liquid, are decomposed, with perhaps the 

 single exception at present known of periodide of mercury 

 (679. 691.) ; and even water itself, which so easily yields up 

 its elements when the current passes, if rendered quite pure, 

 scarcely suffers change, because it then becomes a very bad 

 conductor. 



677. If it should hereafter be proved that the want of de- 

 composition in those cases where, from chemical considera- 

 tions, it might be so strongly expected (669. 674. 672.), is 

 due to the absence or deficiency of conducting power, it would 

 also be proved, at the same time, that decomposition depends 

 upon conduction, and not the latter upon the former (413.); 

 and in water this seems to be very nearly decided. On the 

 other hand, the conclusion is almost irresistible, that in elec- 

 trolytes the power of transmitting the electricity across the 

 substance is dependent upon their capability of suffering de- 

 composition ; taking place only whilst they are decomposing, 



* With regard to solution, 1 have met with some reasons for supposing 

 that it will probably disappear as a cause of transference, and intend re- 

 suming the consideration at a convenient opportunity. 



