attery are practically the same whether
pure oxygen and hydrogen or air and gases containing 25 per cent. of
hydrogen are used; but we found that the latter gases must be
practically free from carbonic oxide and hydrocarbons, which both
interfere very much with the absorbing power of the platinum black.

We had thus to find a cheap method of eliminating these two gases from
the producer gas, and converting them at the same time into their
equivalent of hydrogen. The processes hitherto known for this purpose,
viz., passing a mixture of such gases with steam over lime (which I
mentioned some time ago) or over oxide of iron or manganese, require
high temperatures, which render them expensive, and the latter do not
effect the reaction to a sufficient extent for our purpose.

We have succeeded in attaining our object at a temperature below that
at which the gases leave my producers, viz., at 350 deg. C. to 450 deg. C., by
passing the producer gases, still containing a considerable excess of
steam, over metallic nickel or cobalt. These metals have the
extraordinary property of decomposing almost completely, even at the
low temperature named, carbonic oxide into carbon and carbonic acid
and hydrocarbons into carbon and hydrogen.

In order to carry the process out with small quantities of nickel and
cobalt, we impregnate pumice stone or similar material with a salt of
nickel or cobalt, and reduce this by means of hydrogen or producer
gas. These pieces of pumice stone are filled into a retort or chamber
and the hot gases passed through them. As the reaction produces heat,
it is not necessary to heat the chambers or retorts from the outside
when the necessary temperature has once been attained. This process
has not yet been carried out on a large scale, but the laboratory
experiments have been so satisfactory that we have no doubt as to its
complete success. It will enable us to obtain gases containing 36 per
cent. to 40 per cent. of hydrogen and practically free from carbonic
oxide and hydrocarbons from producer gas at a very small cost, and
thus to make the latter suitable for the production of electricity by
our gas battery. We obtain, as stated before, 50 per cent. of the
energy in the hydrogen absorbed in the battery in the form of
electricity, while, if the same gas was consumed under steam boilers
to make steam, which, as I have shown before, could in this way be
raised cheaper than by burning fuel direct, and if this st