Thermo-electric Action of Metals in Electrolytes. 265 



different electrolytes at 60 F., of different specific gravities, and not 

 mutually decomposable, are placed end to end upon each other as 

 distinct strata in mutual contact, the lighter one being the upper- 

 most, and the junction of the two is heated, a thermo-electric current 

 is produced. He has also shown that this current varies in strength 

 with the kind of solution and the degree of its concentration. That 

 the electromotive force of the resulting current is nearly proportional 

 to the difference of temperature up to that of 50 of the portions 

 of liquid at the contact surface. That with two portions of solution 

 of different degrees of strength of the same salt, the current passes 

 from the weaker to the stronger one. And that when equal volumes 

 of the two solutions contain chemically equivalent weights of salts of 

 two different metals, the order of the liquids in electric tension series 

 is the same as that of their metals. Further, that the order of the 

 series with solutions of all neutral salts of the type R.S0 4 , agrees 

 with that of the ordinary chemico-electric series of their metallic bases 

 in the case of salts of K, Na, Mg, Mn, Fe, Ni, CO, Zn, Cn, and Ag, 

 thus : 



Table IX. 



Thermo-electric Chemico-electric 



Series. Series. 



K 2 S0 4 K 



MgSO 4 Mg 



ZnSO 4 Zn 



FeS0 4 Fe 



NiS0 4 Ni 



CuS0 4 Cu 



Solutions of the salts KC1, KBr, KI, also follow a similar order, but 

 those agreeing with the formula B 2 3 S0 3 do not obey this rule, nor 

 do acids in general. 



E. Becquerel also (" Annales de Chimie et de Physique," 4th series, 

 1866, vol. vii, pp. 392 397) similarly heated the mutual contact 

 portions of two electrolytes about 10 to 80, and found the following 

 effects : A saturated solution of sulphate of copper was positive to a 

 mixture of 1 part of sulphuric acid and 19 parts of water ; water 

 acidulated with hydrochloric acid was positive to a solution of sodic 

 chloride, rendered alkaline by caustic potash ; strong nitric acid was 

 positive to a solution of 1 part of caustic potash in 10 parts of water ; 

 solution of cadmium sulphate was positive to a dilute one of ammonic 

 chloride, and no current was produced by heating the junction of a 

 solution of persulphide of potassium and a diluted one of the same salt. 



One of the chief objects of this research being to obtain new 

 knowledge respecting the relation of thermo-electric action of 

 liquids and metals to chemico-electric action, the chemico-electric 



