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,
and it is repeated until the accumulation of sulphur in the oxide is
so great (45 to 55 per cent.) that it can be profitably sold to the
vitriol maker. Hawkins discovered that by introducing about 3 per
cent. of air into the gas before passing it through the purifiers, the
oxygen of the air introduced set free the sulphur from the iron as
fast as it was absorbed. Thus the process of revivification could be
carried on in the purifiers themselves simultaneously with the
absorption of the sulphur impurities in the gas.
A great saving of labor was thus effected, and also an economy in the
use of the iron oxide, which in this way could be left in the
purifiers until charged with 75 per cent.
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