DETERMINING THE CONSTANTS OF A VOLTAIC CIRCUIT. 
317 
The following measures were obtained when peroxide of manganese was substi- 
tuted for the peroxide of lead. The peroxide of manganese was deposited on a pla- 
tinum plate which formed the positive electrode of a decomposing cell containing a 
solution of chloride of manganese. 
Amalgam of zinc . . Diluted sulphuric acid. Peroxide of manganese . 54 turns. 
Amalgam of potassium Diluted sulphuric acid. Peroxide of manganese . 84 turns. 
A weak current is produced by employing a clean platinum plate in conjunction with 
one covered with the peroxide, in which combination the former acts the part of 
zinc. In this case the positive metal undergoes no chemical action, but on the ne- 
gative side the peroxide is reduced by the evolved hydrogen. 
8. The following measures conclusively show, that if three metals be taken in their 
electro-motive order, the electro-motive force of a voltaic element, formed of the two 
extreme metals, is equivalent to the sum of the electro-motive forces of the two 
elements formed of the adjacent metals. 
Amalgam of potassium . 
Amalgam of zinc . . . 
Amalgam of potassium . 
Amalgam of potassium . 
Amalgam of zinc . . . 
Amalgam of potassium . 
1. 
Sulphate of zinc . . 
Sulphate of copper 
Sulphate of copper 
2 . 
Sulphate of zinc . . 
Chloride of platinum 
Chloride of platinum 
Amalgam of zinc 29 turns. 
Copper ... 30 turns. 
Copper . . .59 turns. 
Amalgam of zinc 29 turns. 
Platinum ... 40 turns. 
Platinum ... 69 turns. 
9. I wished to compare the electro-motive force of a thermo-electric element, the 
two metals of which were bismuth and copper, and whose opposite joints were ex- 
posed to the fixed temperatures of 32° and 212°, with that of a standard voltaic ele- 
ment. As the interposition of the galvanometer greatly reduced the force of the 
current in the thermo-electric circuit, so that I could not advance the needle to 45°, 
I employed, instead, the reduction of the needle from 10° to 5°. The ratios of the 
measures of the electro-motive forces remain the same between whatever two points 
the needle is made to vary, provided they do not change during the same series of 
experiments. 
Thermo-electric element of bismuth and copper, the tempera- ') g 
tures of the joints being 32° and 212° J 
Standard voltaic element of amalgam of zinc, sulphate of cop- 4 
, I 75/ turns, 
per, and copper J 
The relative electro-motive forces are therefore as 1 : 94*6*. 
* Pouillet, by a very different process, has ascertained this proportion to be as 1 : 95. 
Physique Experimentale, 3‘* me ed. tom. i. p. 631. 
See Elemens de 
2 t 2 
