IMPROVEMENTS IN THE PURIFICATION OF GAS, AND THE PRODUCTION OF Bye- PRODUCTS THEREFROM
Year: 1878

page_text: "
PROVISIONAL SPECIFICATION left by Roger William Wallace and George
Christopher at the Office of the Commissioners of Patents on the 17th January
1878.
ROGER WILLIAM WALLACE, of 60, Mark Lane, in the City of London, and
GEORGE CHRISTOPHER, of Clapham, in the County of Surrey, Consulting Chemist,
IMPROVEMENTS IN THE PURIFICATION OF GAS, AND THE PRODUCTION OF Bye-
PRODUCTS THEREFROM."
This Invention relates to the purification of coal and other gases from sulphu-
retted hydrogen, and the production therefrom in an available form of the sulphur
contained therein; also the production of other valuable bye-products.
In carrying our said Invention into practice with respect to coal gas, we first free
it from ammonia as completely as possible by any convenient process in order that
a metallic sulphide may not be precipitated in the process herein-after described.
The gas is then passed through a series of washers or scrubbers containing a solution
of sesqui-chloride of iron (commonly termed per-chloride of iron) or any other metallic
solution on which sulphuretted hydrogen would have a similar effect in converting
a sesqui-salt into a proto-salt with precipitation of sulphur, such for instance as
sesqui-sulphate of iron. It is necessary that the said solution be sufficiently acid to
prevent the precipitation of a metallic sulphide. As this solution is corrosive it is
desirable to construct the washer or scrubber of such materials as will resist the
action of the acid, such for instance as lead, earthenware, stoneware, or wood, or,
if corrodible materials are used, we propose to coat them with some acid-resisting
film.
In employing a solution of per-chloride of iron when, through the action of the
sulphuretted hydrogen in the gas, only a small quantity of the iron remains in the
state of per-chloride, the remainder having been converted into proto-chloride of iron,
and the corresponding quantity of sulphur precipitated, we pass the solution through
any convenient filter, and wash and utilize the sulphur thus filtered off. We then
revivify the solution by exposing it to the action of air either in a scrubber or
washer, through which air is passed, or by exposure to air in shallow pans or other
vessels. We repeat this process indefinitely, adding a small quantity of acid from
[Price 2d

page_text: time to time, as may be found necessary, owing to the possible gradual neutraliza-
tion of the acid originally present by the admission of small quantities of ammona
with the gas.
In order to prevent the scrubbers or washers from becoming blocked up with
sulphur, we may, if found desirable, filter the solution from time to time before it
becomes exhausted.
We may also employ a solution of a salt of chromic acid, such as chromate or
bichromate of potash acidulated sufficiently by some acid which forms a soluble
sesqui-salt of chromium. In this latter method the chromic acid becomes reduced
by the action of the sulphuretted hydrogen to chromic oxide, which forms a sesqui-
salt of chromium with the acid present whilst sulphur is precipitated. This sulphur
is treated as described in the first part of this Specification.
The solution of sesqui-chloride of chromium formed we employ for the preparation
of various other compounds of chromium.
We wish it to be understood that we do not confine ourselves to the purification
of coal gas by the herein-described processes, but may also apply our Invention to the
purification of other gases containing sulphuretted hydrogen, and to the utilization
of the sulphur present, such as the mixture of gases given off from the saturator in
the manufacture of sulphate of ammonia. The carbonic acid present we afterwards
utilize for the production of carbonates of soda, potash, or ammonia by any con-
venient process.