176 Dr. C. R. A. Wright on the Determination of 



60. Various determinations Lave been made of the E.M.F. 

 which a Grove's gas-battery can generate under various con- 

 ditions. When the gases are oxygen and hydrogen, it has 

 uniformly been found that the E.M.F. generated is less than 

 1*50 volt, the value representing the work done in the union 

 of ordinary gaseous oxygen and hydrogen to form liquid 

 water, which is the end result of the action taking place in 

 such a cell when it generates a current. Recently Osgood 

 Pierce (Wied. Annalen, viii. p. 98, 1879) has found numbers 

 varying from -766 to -926 Daniell cell (-84 to 1*02 volt), 

 according to the temperature, the nature of the liquid present, 

 the purity of the oxygen, &c. C ceteris paribus, increasing 

 the temperatures lowers the E.M.F ; Morley has recently 

 shown (Proceedings Physical Society, ii. p. 212, 1878) that 

 when a Grove gas-battery produces a current the E.M.F. is 

 not constant, but is a function of the current produced, being 

 the smaller the greater the current, i. e. the less the external 

 resistance, and vice versa. 



61. A clear coherent explanation of the differences in the 

 numerical values of these quantities obtainable under various 

 conditions, accounting quantitatively for them, and consistent 

 with well-known dynamical principles, does not appear as yet 

 to have been brought prominently forward ; the following 

 attempt in that direction is the result of a somewhat prolonged 

 experimental investigation, some of the results of which are 

 detailed subsequently. 



Theorem. — Were it possible that the surface-action of the 

 electrodes, the chemical action of substances dissolved in the 

 fluid electrolysed, or of the electrode materials themselves, and 

 other interfering causes (such as the accumulation of fluids 

 of different densities round the electrodes) could be entirely 

 eliminated, the primary effect of electrolysis would be to break 

 up the electrolyte into "nascent" products, the formation of 

 which would correspond to a definite amount of ivork, and con- 

 sequently to a definite E.M.F. ; but the physical attraction 

 exerted by the electrodes upon the nascent products causes 

 a certain proportion of them (variable with circumstances) to 

 be converted ab initio into products, the formation of which 

 from the u nascent " products is accompanied by a gain of 

 energy (or evolution of heat). Similarly, under certain con- 

 ditions the products of electrolysis are chemically acted upon 

 by the electrodes, or by gases occluded upon their surfaces, 

 substances dissolved in the fluid electrolysed, &c. ; whilst, as 

 the action proceeds, solutions of different densities accumulate 

 round the electrodes, tending to set up an E.M.F. in virtue 

 of their interdiffusion. All these circumstances modify the 



