1892.] Voltaic Cells with Fused Electrolytes. 83 



As regards these currents due to difference of temperatures, Andrews 

 concluded, from the non-corrosion of the platinum wires used by him, 

 that the action was in his experiments thermo-electric. Gladstone 

 and Tribe state that in their experiments " it is difficult to imagine 

 that chemical action in any way initiates the current." Their experi- 

 ments show clearly, however, that the phenomenon is of electrolytic 

 nature, since the current formed is accompanied by the solution of 

 metal at the hot side, and its deposit in crystalline form at the cooler 

 electrode. The same effect was also observed in my experiments with 

 copper in its fused double chloride ; a large deposit of crystalline 

 metal was found on the cooler wire after the current had passed for 

 an hour. The action must, therefore, be of electrolytic or voltaic 

 character ; and the application of Thomson's law to these unequally 

 heated cells would suggest that, with the apparent exception of 

 cadmium, there is an increase with temperature of the heats of com- 

 bination of the metals with chlorine, conjoined with a possible Peltier 

 effect. Such a variation is, in fact, well ascertained in other cases ; 

 and Thomson* gives a formula for its calculation from the specific 

 heats of the bodies involved. The want of data for the fused salts 

 prevents its further discussion here. 



Assuming this variation of the heats of combination to exist, and 

 assuming, also, that the chemical energy is all adjuvant at the various 

 temperatures,! we could directly account for the additive corrections 

 empirically deduced from Table I and applied in Table II, the num- 

 bers in Table I being founded on Thomsen's heats of combination 

 obtained at 18 to 20, while ray experiments were made at tempera- 

 tures several hundred degrees higher. It will thus be important to 

 determine the temperature co-efficients of these cells, and I hope to 

 do so at some future time. 



Another point demanding careful attention is the extent to which 

 these cells are reversible. The following experiments bear on this 

 subject : 



Two clay tobacco pipes were clipped by their stems in wooden 

 supports, one in each, and placed with their bowls touching and 

 facing upwards. One contained some melted zinc, and the other 

 melted tin, with iron connecting wires through the stems. The 

 respective chlorides were fused over these metals and connected 

 together by a bunch of asbestos, a notch having been cut at the point 



* ' Thermochem. Untersuchungen,' vol. 2, p. 54. 



f [This assumption is of course provisional. It was necessary because of the 

 absence of any investigation here as to what part, if anv, of the energy is non- 

 adjuvant. Helmholtz and other well-known authors have discussed this question 

 in connexion with the ordinary aqueous form of cell, but I have not attempted its 

 investigation as yet in the present case. When the temperature coefficients and 

 other data have been obtained this may be undertaken. Aug. 2, 1892.] 



G 2 



