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 

 to the zinc. 



Well-burned charcoal clamped 

 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 

 to the zinc. 

 3-2 



Hard carbon from gas retorts 

 clamped to the zinc. 

 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 3-4 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, plumbago, or hard carbon, 



* The battery consisted of four zinc cylinders, each having 6^ inches 

 surface, and the pipeclay cups, 1 inch in diameter and \^ inch long, which 

 gave the above quantity of gas in two minutes. 



