470 Mr. R. Colley on a Case of Work 



Relying on this principle, and on the laws of Faraday and 

 Joule, we can prove theoretically that any work produced by 

 the current is always accompanied by the appearance in the 

 circuit of a new electromotive force opposed to that of the 

 pile. This result has been confirmed by experiment in all 

 cases hitherto studied : in electromagnetic motors induction- 

 currents weaken the primary current; chemical work, the 

 separation of the elements of a chemical compound, is always 

 accompanied by the manifestation of the electromotive force 

 called " polarization," &c. If, on the contrary, the experi- 

 ment can be arranged so as to employ external work to re- 

 inforce the primary current, the new electromotive force will 

 evidently be of the same sign as that of the pile. This is 

 what would happen if, for example, by the exertion of our 

 arms we were to impress on the electromagnetic motor a 

 motion in the opposite direction to that which it would have 

 taken under the influence of the current. 



The aim of the work I have undertaken was, to apply these 

 principles to a case hitherto not investigated, and to confirm 

 by experiment the existence of this force, which cannot at 

 present be classed in any category of known electromotive 

 forces, but must be regarded as a new one. 



Let us imagine the following experiment. The current of 

 a Daniell element passes up through a vertical tube filled with 

 any electrolyte (a solution of nitrate of silver, for instance), 

 entering and issuing from the liquid by electrodes of metallic 

 silver, and moreover traverses a galvanometer. A quantity 

 of silver equivalent to the zinc dissolved in the pile will dis- 

 solve at the lower and be deposited on the upper electrode. 

 The transport of this metal upward in opposition to its weight 

 constitutes work produced by the current. Nevertheless this 

 work is always accompanied by work of opposite sign, due to 

 the transport in the opposite direction of the group of atoms 

 which in the electrolyte were combined with the metal. This 

 work is manifested by a diminution of concentration of the 

 salt in the immediate vicinity of the negative electrode, and a 

 corresponding augmentation near the positive electrode. Hit- 

 torf 's experiments * on the transport of the products of elec- 

 trolysis by the current supply the necesssary empiric data for 

 calculating the numerical value of this work. It is found that 

 for most salts (among others, for nitrate of silver) this work 

 is less than that of the transport of the metal. There are, 

 however, two iodides, those of zinc and cadmium, in which 



* Poggendorft's Annalen, vols, lxxxix., xcviii., ciii., cvi. See also 

 Wiedemann, Gakanismus, 2nd ed., vol. i. p. 555. 



