AN IMPROVED METHOD OF ABSORBING SULPHUROUS FUMES OR SULPHUROUS ACID AND OBTAINING THEREBY USEFUL PRODUCTS
Year: 1870

page_text: PROVISIONAL SPECIFICATION, left by Michael Cahen at the Office of
the Commissioners of Patents, with his Petition, on the 4th July
1870.
I, MICHAEL CAHEN, of Mulheim on Rhine, in the Kingdom of Prussia,
Engineer, do hereby declare the nature of the said Invention for "AN
IMPROVED METHOD OF ABSORBING SULPHUROUS FUMES OR SULPHUROUS ACID AND
OBTAINING THEREBY USEFUL PRODUCTS," to be as follows:-
:―
The sulphurous fumes evolved in the roasting of metallic sulphites
infect the atmosphere, are hurtful to human and animal life, and
destructive to vegetation. Further their volatilization results in a great
waste of useful material, for example, a smelting house producing daily
ten tons of spelter out of blende gives off an equal quantity of sulphur in
the form of sulphurous acid.
The object of my Invention is to arrest these fumes by such means
that the product becomes valuable for manufacturing purposes.
My method is based upon the transformation of the oxides of manganese
or of metallic iron into salts of manganese or iron by more or less rapid
absorption of sulphurous acid.

page_text: The oxides of manganese which contain a certain proportion of peroxyde
have especially the property of instantly combining with sulphurous acid,
and I therefore propose to employ peroxydes of inferior quality which may
be obtained at a low price, but should these become too costly I can make
use of other oxides of manganese without peroxyde, or I may use metallic
iron.
The absorption may be effected in a superficial manner by leading the
sulphurous fumes over fragments of dry peroxyde, but for more complete
absorption the peroxyde should be kept moistened and be cleansed from
time to time of the lie and the impurities which deposit themselves on
the surface; or otherwise the sulphurous acid may be condensed in
water and the solution allowed to act on the substances. The salts
thus formed are combinations of the protoxyde of manganese with
hyposulphuric acid, sulphuric acid, and sulphurous acid. These salts.
are at present of little commercial value in themselves, but very valuable
products are obtained by their aid. For example, if the solution of these
salts is mixed with a solution of common salt the mutual interchange of
acids and bases gives soda salts and chloride of manganese. Hypo-
sulphate of soda crystallises out of a but slightly concentrated solution at
the ordinary temperature, sulphate of soda by a sufficient decrease of
temperature. The sulphite of protoxyde of manganese which is insoluble
in water, slowly roasted with common salt, gives sulphate of soda, oxyde
of manganese (mn 3º4), while hydrochloric acid is evolved. The soda
salts thus produced may be employed in the manufacture of carbonate
of soda, some of them have already more valuable uses, and their appli-
cation will be greatly extended as they become cheaper.
My new method will not only be found valuable in smelting houses
now giving forth their sulphurous acid to waste, but also in works
burning sulphur or iron pyrites to produce sulphate of soda, and in other
factories.