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XXIV. Relation of Volta Electromotive Force to Latent Heat, 

 Specific Gravity, fyc. of Electrolytes. By Dr. Gr. GrORE, 

 F.R.S.* 



I~N a research " On Changes of Voltaic Energy of Alloys 

 during Fusion " (Phil. Mag. ante, p. 27) I have shown 

 that when an alloy of bismuth, lead, tin, and cadmium, and 

 one of bismuth, lead, and tin, changed from the solid to 

 the liquid state by gradual and uniform application of 

 heat whilst immersed in a suitable electrolyte, it suddenly 

 increased in electropositive state, showing that whilst ab- 

 sorbing latent heat it acquired greater electromotive force, 

 and that when these alloys solidified, reverse effects occurred. 

 M. J. Regnauld had previously shown ( Comptes Rendus Acad. 

 Sci. June 10, 1878 ; Chemical News, vol. xxxviii. p. 33) that 

 liquid gallium was electropositive to solid gallium in a neutral 

 solution of gallous sulphate. 



In order to ascertain whether, in cases where the mere act 

 of mixing or diluting electrolytes is known to be attended by 

 absorption of heat, a similar increase of the power of exciting- 

 electromotive force occurs, I took the separate ingredients 

 of a chilling-mixture, each in a liquid state and at the same 

 atmospheric temperature, measured the electromotive force 

 of a simple couple of cadmium and platinum f in each liquid 

 separately by the null method of balance, with the aid of a 

 suitable thermoelectric pile (see Proc. Birm. Phil. Soc. vol. iv. 

 p. 130 ; The Electrician, 1884, vol. xii. p. 414), and a galva- 

 nometer, then mixed the liquids, immediately took the tem- 

 perature of the mixture, and, after having allowed the liquid 

 to acquire the atmospheric temperature, measured the electro- 

 emotive force of the couple in it. As the changes of energy 

 depend upon each of the ingredients of the mixture, it was 

 necessary in each case to consider the alterations of the mean 

 amount of electromotive force. 



Distilled water was used in making all the solutions. The 

 proportions of substances employed were in nearly all cases 

 simple multiples of their equivalent weights. The thermo- 

 meter employed in the first four experiments was graduated 

 to *2 of a Fahr. degree, and that used in all the other ones 

 was capable of being read to *01 of a Centigrade degree. The 

 following are the particulars of the experiments : — 



* Communicated by the Author. 



t In experiments " Nos. 7 and 15 " a zinc-platinum couple was used. 



