42^]^ Mr. Smee on the Amalgamation of Zinc, 
ode, at which oxygen is evolved, and the hydrogode, where the 
hydrogen is given off. 
The soft and spongy charcoals, as those of deal, possess the 
property of evolving gas very imperfectly. 
Various kinds of coal, such as anthracite and cannel, were 
tried, but none were found to evolve hydrogen, nor to have 
copper precipitated when the circuit was made in a solution of 
that metal. 
From the above experiments we see that batteries may be 
constructed of carbon in the place of a negative metal ; the 
hard coke or plumbago answering best, and the porous coke 
and box-wood charcoal next*. These may be used as an 
ordinary battery with sulphuric acid, but of course a battery 
thus constructed possesses but little power. If, however, the 
hydrogen is removed upon Professor Daniell’s principle, then 
will the power be increased, and a charcoal battery may be 
made of surprising energy. The hydrogen may be removed 
by metallic solutions which have a feeble affinity for oxygen, 
and therefore those of gold, silver, platinum, or copper would 
answer best; the latter being the only one in use from its 
cheapness. The highly oxygenated acids, such as nitric, &c., 
are more powerful than these, and are now considerably em- 
ployed, but disadvantages attend their action ; for if the cur- 
rent is required to be continued for a long time, a large quan- 
tity of acid must be used, and the fumes arising from the 
battery are injurious to the animal oeconomy: in addition, the 
strong acid is liable to be spilt over the fingers or clothes ; and 
lastly, it always transudes through the porous tubes and acts 
upon the zinc, even when amalgamated, to a considerable 
extent. 
It is perhaps worthy of notice, that the powers of the nitric 
acid battery are not to be attributed to the fluids alone, for no 
current is formed when platinum is used in both cells. Strong 
sulphuric acid produced scarcely any action, but the addition 
of nitric acid rendered it powerful, for a time proportionate 
to the quantity of the latter acid used. I have tried other 
substances which have an affinity for hydrogen, such as chlo- 
rine, iodine, chloride of lime, peroxide of iron (or a mixture 
of muriatic acid and peroxide of manganese), so that nascent 
chlorine may be evolved during the action of the battery; but 
I find that even with the latter, the action, though powerful, 
is one quarter less than with strong nitric acid. 
A coke battery of two cells, with eight ounces of nitric 
* The coke may be cut with a saw into any convenient shape, whilst 
plumbago, though softer, has the singular property of wearing down every 
tooth from the instrument in a very short time. 
