362 M. Becqiierel on an Electro-magnetic Balance^ 



the relations by which affinities are connected with the electric 

 forces. Since the discoveries made by Mr. Faraday on the 

 nature and extent of electro- chemical decomposition, we know 

 that the chemical power of a current is in the direct ratio of 

 the absolute quantity of electricity which is in motion. It is 

 by resting on this principle that he succeeded in his endeavours 

 to determine the equivalents of bodies ; but in his researches 

 he disregarded the absolute intensity of the force that is in ac- 

 tion at each instant. This is the defect which I have sought to 

 supply by means of my apparatus. It has long been remarked 

 that the elements which are combined with the greatest energy 

 are also decomposed with the greatest readiness by currents, 

 and that the elements which are combined in consequence of 

 feeble affinities are those which offijr the most obstinate resist- 

 ance to the decomposing action of electricity in motion. It 

 seems to follow from this circumstance that all compound 

 bodies are dissolved under the influence of a current propor- 

 tioned to the force of the affinity by which their elements are 

 united. If then we could establish a relation between the in- 

 tensity of this current and affinity, we should be enabled to 

 measure the latter. In researches of this kind due attention 

 must be paid to the following observations of Mr. Faraday : 

 1st, that the electric powers as well as the chemical action of 

 electricity are definite; 2nd, that a considerable quantity of 

 electricity in the form of a current decomposes but a small 

 quantity of elements ; 3rd, that the electric agent is employed 

 only for the purpose of overcoming the electro-chemical powers; 

 whence it may be inferred that the quantity which passes is at 

 least equal to the quantity possessed by the separate mole- 

 cules ; 4-th, that there is a perfect accordance between the 

 theory of definite proportions and that of electro-chemical 

 affinity, whence it follows that the equivalent parts of bodies 

 may be considered as volumes possessing equal quantities of 

 electricity, or at least equal electric powers. The atoms of 

 bodies which are equivalent to each other in their ordinary 

 chemical action have therefore equal quantities of electricity 

 combined with them. The following are the experiments 

 which I made in order to arrive at the solution of the problem 

 which I proposed to myself. 



When a constant current is made to pass into two differ- 

 ently saturated solutions of a salt with a reducible base, the 

 quantity of salt decomposed is exactly the same in both. I 

 took 2K'"in'8 (= 43*25 grs. nearly) of dry nitrate of copper and 

 dissolved it in 10»'''"'3 (= about 6 fluidrachms) of water: half 

 the solution was diluted by a quantity of water equal to it in 

 volume ; the two copper wires plunged into the two negative 



