94 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XII.) 



of those extensive sciences, which are occupied in considering the forces of the par- 

 ticles of matter, to fall into much closer order and arrangement than they have here- 

 tofore presented. 



1355. Another point is, the facilitation of electrolytic conducting power or dis- 

 charge by the addition of substances to the dielectric employed. This effect is 

 strikingly shown where water is the body whose qualities are improved, but, as yet, 

 no general law governing all the phenomena has been detected. Thus some acids, as 

 the sulphuric, phosphoric, oxalic, and nitric, increase the power of water enormously; 

 whilst others, as the tartaric and citric acids, give but little power ; and others, again, 

 as the acetic and boracic acids, do not produce a change sensible to the voltameter 

 (739.). Ammonia produces no effect, but its carbonate does. The caustic alkalies 

 and their carbonates produce a fair effect. Sulphate of soda, nitre (753.), and many 

 soluble salts produce much effect. Percyanide of mercury and corrosive sublimate 

 produce no effect ; nor does iodine, gum, or sugar, the test being a voltameter. In 

 many cases the added substance is acted on either directly or indirectly, and then 

 the phenomena are more complicated ; such substances are muriatic acid (758.), the 

 soluble protochlorides, (766.), and iodides (769.), nitric acid (752.), &c. In other 

 cases the substance added is not, when alone, subject to or a conductor of the powers 

 of the voltaic battery, and yet both gives and receives power when associated with 

 water. M. de la Rive has pointed this result out in sulphurous acid''^^, iodine and 

 bromine-}- ; the chloride of arsenic produces the same effect. A far more striking 

 case, however, is presented by that very influential body sulphuric acid (681.) ; and 

 probably phosphoric acid also is in the same peculiar relation. 



1356. It would seem in the cases of those bodies which suffer no change them- 

 selves, as sulphuric acid (and perhaps in all), that they affect water in its conducting 

 power only as an electrolyte; for whether little or much improved, the decomposi- 

 tion is proportionate to the quantity of electricity passing (727- 730.), and the transfer 

 is therefore due to electrolytic discharge. This is in accordance with the fact already 

 stated as regards water (984.), that the conducting power is not improved for 

 electricity of force below the electrolytic intensity of the substance acting as the di- 

 electric ; but both facts (and some others) are against the opinion which I formerly 

 gave, that the power of salts, &c. might depend upon their assumption of the liquid 

 state by solution in the water employed (410.). It occurs to me that the effect may 

 perhaps be related to, and have its explanation in differences of specific inductive ca- 

 pacities. 



1357. I have described in the last paper, cases, where shell-lac was rendered a 

 conductor by absorption of ammonia (1294.). The same effect happens with mu- 

 riatic acid ; yet both these substances, when gaseous, are non-conductors ; and the 



* Quarterly Journal, xxvii. 407. or Bibliotheque Universelle, xl. 205. Kemp says sulphurous acid is a very 

 good conductor. Quarterly Journal, 1831, p. 613. 



t Quarterly Journal, xxiv. 465. or Annales de Chimie, xxxv. 161. 



