off in an
hour, and from one charge a yield of about 2,000 cub. ft. is obtained.
With a less perfect vacuum the time is longer--even as much as four
hours. The whole operation of charging and exhausting the retorts can
be completed in from three to four hours. As soon as the evolution of
oxygen is finished, the doors, K, and ventilators, L, may be opened
and the retorts cooled for recharging.

The cost of producing oxygen at Westminster, under specially expensive
conditions, is high--about 12s. per 1,000 cub. ft. When we consider,
however, that the cost should only embrace attendance, fuel, wear and
tear, and a little lime and soda for the purifiers, that the
consumption of fuel is small, the wear and tear light, and that the
raw material--air--is obtained for nothing, it ought to be possible to
produce the gas for a third or fourth of this amount in most of our
great manufacturing centers, where the price of fuel is but a third of
that demanded in London, and where provision could be made for
economizing the waste heat, which is entirely lost in the Westminster
installation. Moreover, in estimating this cost all the charges are
thrown on the oxygen; were there any means of utilizing the 4,000 cub.
ft. of nitrogen at present blown away as waste for every thousand
cubic feet of oxygen produced, the nitrogen would of course bear its
share of the cost.

The question of the application of the oxygen is one which must be
determined in its manifold bearings mainly by the experiments of
chemists and scientific men engaged in industrial work. Having
ascertained the method by which and the limit of cost within which it
is possible to use oxygen in their work, it can be seen whether by
Brin's process the gas can be obtained within that limit.

Mr. S.R. Ogden, the manager of the corporation gasworks at Blackburn,
has already made interesting experiments on the application of oxygen
in the manufacture of illuminating gas. In order to purify coal gas
from compounds of sulphur, it is passed through purifiers charged with
layers of oxide of iron. When the oxide of iron has absorbed as much
sulphur as it can combine with, it is described as "foul." It is then
discharged and spread out in the open air, when, under the influence
of the atmospheric oxygen, it is rapidly decomposed, the sulphur is
separated out in the free state, and oxide of iron is reformed ready
for use again in the purifiers. This process is called revivification,