Thermo-electric Action of Metals in Electrolytes. 257 



time usually occupied varied from one to two minutes. All the 

 measurements, except those of Tables XI and XIV (pp. 273 and 277), 

 were made by balancing the current to be measured, by one of equal 

 potential from two thermo-electric piles, each consisting of about 

 300 pairs of iron and German silver wires, the accuracy of which was 

 occasionally tested by means of a Clark's standard cell.* (For a 

 description of the pile, see " Proc. Birm. Phil. Soc.," vol. iv, pt. 1.) 



With the two pieces of metal at 60 and 160' F. respectively, the 

 following numbers and series were found, in which the top couple of 

 the upper section is the most positive, and the bottom one of the lowest 

 division is the most negative. 



Table III. Electric Potentials of Thermo-electric Couples. 



Metal. Liquid. Volts. 



Al Na 2 HP0 4 -6621 



Formic acid '4392 



HN0 3 -4317 



Ni Tartaric acid '3447 



Al HC10 3 -3051 



KF -2914 



H 2 S0 4 -2778 



Ni K 2 S0 4 -2428 



Am alum '1972 



Sn KCy '1827 



Ni MgS0 4 ... -1757 



Fe KBr 1702 



Ni KC1 -1439 



HC1 -0978 



Na 2 S0 4 -0975 



Cd . KHO. . -0877 



Total 4 1475 



Average '2592 



Pb MgS0 4 -0119 



Au HC1 -0140 



Formic acid '0236 



Mg KI -0282 



Pt Na 2 S0 4 -0324 



Pd Am alum '0441 



Au K 2 S0 4 -0504 



HNO 3 -0660 



* Nearly all the measurements of potential in this research were made with the 

 aid of a Thomson's reflecting galvanometer, having a resistance of 3040'7 ohms. 



