36 On the Employment of Carbon in Voltaic Combinations. 
acid as nearly an equal surface as it was possible to obtain *. 
The figures represent the volumes of gas obtained by the vol- 
tameter in equal times. 
Thick platinum foil soldered 
\Vell-bm*ned charcoal clamped 
to the zinc. 
to the zinc. 
3*4 
2*8 
3*4 
3*0 
3*4 
3*1 
3*6 
3*2 
3*6 
3*25 
3*5 
3*25 
3*75 
3*25 
3*5 
3*4 
3*5 
3*25 
9)31-65 
9)28*50 
Mean 3*517 cub. inch. 
Mean 3*17 cub. inch. 
Plumbago clamped 
Hard carbon from gas retorts 
to the zinc. 
clamped to the zinc. 
3*2 
2*6 
3*2 
2*8 
3*3 
3*3 
3*2 
3*4 
3*2 
3*4 
3*6 
3*45 
3*6 
3*5 
3*7 
3*6 
3*5 
3*4 
9)30*5 
9)29*45 
Mean S‘4< cub. inch. Mean 3*27 cub. inch. 
From the above results it will be evident that the platinum 
appears to possess a trifling advantage over the other sub- 
stances ; this, however, 1 am inclined to ascribe to the more 
perfect contact of the platinum with the zinc by soldering than 
to its superior qualities as a conductor of electricity ; and when 
the difference of expense is taken into consideration in the 
construction of large and extensive combinations, the applica- 
tion of the above-mentioned substances must be regarded as of 
great importance to the chemist, and to those who may have 
occasion to employ such combinations as electro-motors, see- 
ing that either with the charcoal, jffumbago, or hard carbon, 
* The battery consisted of four zinc cylinders, each having 6]^ inches 
surface, and the j)ij)eclay cups, 1 inch in diameter and T} inch long, which 
gave tlie above quantity of gas in two minutes. 
