428 Dr. Faraday's Experimental Researches in Electricity. 



(804.), the conclusion may be drawn, that both the iodine and 

 tin are ions, and that the proportions in which they combine 

 in the fused compound express their electro-chemical equiva- 

 lents. Again, with respect to the fused iodide of potassium 

 (805.), it is an electrolyte; and the chemical equivalents will 

 also be the electro-chemical equivalents. 



841. If proposition viii. sustain extensive experimental in- 

 vestigation, then it will not only help to confirm the results 

 obtained by the use of the other propositions, but will give 

 abundant original information of its own. 



842. In many instances, the secondary results obtained by 

 the action of the 'evolving ion on the substances present in 

 the surrounding liquid or solution, will give the electro-che- 

 mical equivalent. Thus, in the solution of acetate of lead, 

 and, as far as I have gone, in other proto-salts subjected to 

 the reducing action of the nascent hydrogen at the cathode, 

 the metal precipitated has been in the same quantity as if it 

 had been a primary product, (provided no free hydrogen 

 escaped there,) and therefore gave as accurately the number 

 representing its electro-chemical equivalent. 



843. Upon this principle it is that secondary results may 

 occasionally be used as measurers of the volta-electric current 

 (706. 740.) ; but there are not many metallic solutions that 

 answer this purpose well; for unless the metal is easily pre- 

 cipitated, hydrogen will be evolved at the cathode and vitiate 

 the result. If a soluble peroxide is formed at the anode, or 

 if the precipitated metal crystallize across the solution and 

 touch the positive electrode, similar vitiated results are ob- 

 tained. I expect to find in some vegetable salts, as the 

 acetates of mercury and zinc, solutions favourable for this use. 



844. After the first experimental investigations to establish 

 the definite chemical action of electricity, 1 have not hesitated 

 to apply the more strict results of chemical analysis to correct 

 the numbers obtained as electrolytical results. This, it is 

 evident, may be done in a great number of cases, without 

 using too much liberty towards the due severity of scientific 

 research. The series of numbers representing electro-che- 

 mical equivalents must, like those expressing the ordinary 

 equivalents of chemically acting bodies, remain subject to the 

 continual correction of experiment and sound reasoning. 



845. I give the following brief Table of ions and their 

 electro-chemical equivalents, rather as a specimen of a first 

 attempt than as anything that can supply the want, which 

 must very quickly be felt, of a full and complete tabular ac- 

 count of this class of bodies. Looking forward to such a table 

 as of extreme utility (if well constructed) in developing the 



