218 Electromotive Force beticeen Metals in Fused Salts. [Mar. 26, 



the metals (see columns 2 and 4), the copper element consisted of 

 a bent pipe, immersed in the fused salt, through which water 

 was kept flowing, the temperature of the copper being about 

 29° C. The platinum crucible was surrounded by temperatures 

 from 549° to 879° C, a total variation of 850° C. between the two 

 elements was obtained. A similar method was adopted in the 

 platinum and iron experiments. A temperature divergence of about 

 518° C. between platinum and copper gave a reverse E.M.F. of 0*92 

 volt (platinum positive), but with the salt in liquid fusion (platinum 

 at 879° C., copper at 29° C.) a reverse E.M.F. (platinum positive) of 

 only 0'66 volt was obtainable. A temperature variance of about 

 522° C. between platinum and iron yielded an E.M.F. of 0*53 volt 

 (platinum positive), but when the salt was in liquid fusion (platinum 

 879° 0., iron 29° C.) a reverse E.M.F. (platinum positive) of only 

 0'40 volt was noticed. In a cell of this description, two opposing 

 forces were observed in operation, the thermo-electric, contending at 

 the higher temperatures with the normal electro-chemical action of 

 the fused salt. The results of the water pipe experiments, recorded 

 in detail on Table B, show that generally from some cause the extent 

 of the reversed E.M.F. did not appear to correspond in exact pro- 

 portion with the temperature divergences between the metals ; this 

 result may perhaps be accounted for by the electrolyte at the in- 

 creased temperatures combating the thermo-electric influences, and 

 commencing to restore the true electro- chemical equilibrium of the 

 metals. A point of temperature is reached where the thermal effects 

 counterbalance the normal electric action of the fused salt. There is 

 apparently a powerful thermic influence, where equality of tempera- 

 ture does not obtain, reversing the E.M.F. from the metals, notwith- 

 standing their immersion at high temperatures in such electrolytes as 

 fused salts ; this reversal of direction of the current in the case of 

 K 2 C0 3 , continuing even with the salt at a temperature of 695° C, or 

 above, the current passing from the hotter platinum to the colder 

 copper. When, however, the point of fusion of the hot solidified 

 salt is reached (834° C), the metals, being at an uniform temperature 

 therein, resume their true electro-chemical positions. 



The foregoing and other repeated experiments appear to indicate 

 that in the form of apparatus used by the author, these interchanges 

 in the direction of the current between platinum and copper, or 

 platinum and iron, were almost solely caused by differences of tem- 

 perature surrounding the two metals forming the elements. 



