Notice of Faraday s Discoveries in Electro-chemical Decotnposilioi}. 59 



positive conductor of an electro-motive apparatus, and bases to the nega- 

 tive conductor ; therefore (in accordance with the views of Sir H. Davy, that 

 chemical and electrical attractions are really only modifications of the same 

 principle.) acids have been considered as electro-negative, and their bases 

 as electro-positive, and therefore attracted by their opposite poles. Mr. F. 

 however, prefers simply calling the acids in these cases anions, and the 

 bases cations, which merely expresses the fact, witliont implying any hypo- 

 thesis j he calls both constituents by the general name of ions. 



The principal laws which Mr. Faraday has established are these : — 



1. The decomposition of a body necessarily depends on its conducting 

 power, and this often varies iu different states of the same body ; thus 

 there is a class of bodies which, when solid, insulate electricity, (especially 

 under the low intensities induced by galvanic action) but when rendered 

 fluid, conduct it freely, and are decomposed by it 5 thus ice is a non-con- 

 ducting non-electrolyte, water a conducting electrolyte j and the same differ- 

 ences are found in the solid and fluid states of potassa, protoxide of lead, 

 glass of antimony, oxide of bismuth, various chlorides, iodides, and sul- 

 phnrets, and many ordinary neutral salts with alkaline bases : in almost 

 every instance the bodies subjected to this law are electrolytes. Sul- 

 phuret of silver is the only known exception ; although many compound 

 conducting fluids are non-electrolyzable ; yet neither are these subject to 

 the above law of variable conductibility. 



2. Compounds, which may be considered as primary combinations of a 

 single atom of one constituent, united to a single atom of the other, alone 

 constitute the class of electrolytes ; thus protochlorides and protiodides 

 are electrolyzable, but not per-chlorides or per-iodides. 



3. The decomposing action of any current of electricity is constant, for 

 a constant quantity of electricity. 



4. The electrolytic action follows the chemical laws of definite propor- 

 tion ; thus the same current which will decompose a given weight of 

 water, will decompose proportional weights of other electrolytes, intro- 

 duced into the same circuit, corresponding exactly with the proportional 

 numbers representing the respective chcmicai equivalents of these bodies. 

 This has been ascertained with regard to muriatic acid, protochloridc of 

 tin, iodide and oxide of lead, and many other bodies. 



Mr. F. considers the quantity of electricity thus required for the decom- 

 position of an electrolyte, as equivalent to that which, being naturally 

 combined with its constituent ions, previously retained them in union. 

 He estimates this quantity as very great j a single grain of water requiring 

 for its decomposition a quantity of electricity equal to a very powerful flash 

 of lightning ! ! We shall hereafter explain in what manner the galvanic 

 electromotive apparatus, through the almost infinite velocity of the electri- 

 cal current which it set's in motion, although of very low intensity at any 



