66 S. L. Harding—Bichromate of Soda Cell. 
cell of this battery as the unit, the electro-motive force of the 
soda cells tested was as follows: 
1°887 volts. 
1°884 
Average Oy SBE ores 1°893 
The electromotive force of the potash cell in the same way 
was found to be 1°852, while that of the ordinary Daniell’s cell 
—12 parts of water to one of sulphuric acid—was 1:059 volts. 
Resistance. 
Lodge’s method,* a modification of Mance’s method, was 
used in determining the resistance of the cells; a condenser, it in 
some cases of one-third of a microfarad, and, in others, of a 
little over a microfarad in capacity, being used. For the soda 
cell, the resistance was found to be: 
‘494 ohms. 
504 
"495 
"494 
Averageseeene 4967 
Likewise for the potash cell, -468 ohms was the resistance. 
The resistances of both cells could undoubtedly, if occasion 
should demand it, be reduced. 
From the foregoing it is seen that the bichromate of soda 
cell is a most efficient cell; its effectiveness, however, could 
be materially increased, I believe—at least, as far as its con- 
stancy is concerned—by interchanging the positions of the 
electrodes with their surrounding liquids, after the fashion of 
the Fuller cell; that is, placing the zine and sulphuric acid © 
inside the porous cup, and the carbon, with a much increased 
quantity of the depolarizing mixture, outside the cup. 
Jefferson Physical Laboratory, Harvard University, June, 1886. 
* See Phil. Mag. Supplement, June, 1877, p. 515. 
