90 Voltaic Cells with Fused Electrolytes. [June 16, 



G. F. Fitzgerald and to Mr. J. Larmor for several important sugges- 

 tions. 



Since writing the above, my attention has been called to a paper by 

 L. Poincare,* " Sur les Piles a Electrolytes Fondus et sur les Forces 

 Thermo-electriques a la Surface de contact d'un Metal et d'un Sel 

 Fondu." M. Poincare has measured the thermo-electric actions in 

 one or two thermo-cells similar to those which I have described, and 

 finds the following thermo-electromotive forces for a difference of 1 

 between the two metal electrolyte junctions, the sign being that of 

 hotter pole : 



Silver in silver nitrate 0*00027 volt. 



Zinc in zinc chloride + 0*00013 ,, 



Tin in staimous chloride 0*000028 



The sign for tin (Joes not appear to be given ; that for zinc is the 

 reverse of my result. M. Poincare has also measured the electro- 

 motive force of one voltaic cell with fused electrolytes, 



Zinc | ZnCl 2 | SnCl 2 | Tin, 



and finds it to be 0*335 volt. My result, in Table I, when reduced 

 to volts, is 0*350. He finds for the value just after solidification of 

 the electrolyte, 0*37 volt, and considers that, in order to obtain the 

 true heat equivalent of a cell with fused electrolytes, the latent heat 

 of fusion of the salts used should be deducted from Thomson's heats 

 of combination for the solid salts. There would appear to be, on 

 theoretical grounds, some doubt on this point. It could be experi- 

 mentally tested more definitely if data for these heats of fusion were 

 available. 



Synopsis. 



In instituting a comparison of the observed electromotive forces of 

 cells with their theoretical values, as given by Thomson's law, the 

 simpler the construction of the cell the more easy is it to ascertain 

 the nature of the chemical action going on in it, upon which the cal- 

 culation rests. 



In cells with aqueous electrolytes, the solvent introduces several 

 irreducible complications, arising from possible action of the solvent 

 itself as an electrolyte, from the formation of insoluble films (either 

 inactive and protective as oxides, or active, as hydrogen), or from 

 the uncertainty of calculations involving heats of solution of the pro- 

 ducts of voltaic reaction. 



When the liquidity of the electrolyte is produced by fusion instead 



* Comptes Eendus,' vol. 110, p. 339, 1890. 





