Improvements in the Manufacture of Pyro-sulphates.
Year: 1887

page_text: Date of Application, 21st Mar., 1887
Complete Left, 20th Dec., 1887
Complete Accepted, 27th Jan., 1888
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Pyro-sulphates.
I HEINRICH BAUM of Mannheim in the Empire of Germany do hereby declare the
nature of this invention to be as follows:-
The pyro sulphuric salts of the metals, and especially of the alkaline metals
(SO, R) have been hitherto obtained either by Berzelius" method-vizt. heating the
acid or hydro sulphates at a brown heat; or by the action of a molecule of SO, upon
neutral sulphates (R. Weber Berlin Berichte vol 17 page 2498 and H Schulze
page 27056) Owing to its expense, the latter method is scarcely practicable for the
commercial production of pyro-sulphates whilst the former method possesses the
serious drawback that a part of the pyro sulphate formed at the high temperature of
brown heat almost always decomposes evolving SO, Only an inferior product is
obtained by this means, when carried out on a large scale added to which the open
cast-iron melting vessels at the high temperature become very quickly destroyed.
The Inventor of the present process has discovered that the hydro sulphates i c.
those of the alkalies and of ammonia or molecular mixtures of neutral sulphates
with H. SO, in vacuo, become converted at a comparatively low temperature
(260° to 320° C) into pyro-sulphates and liberate water without the formation of the
slightest trace of SO,. At those low temperatures, the operation may be performed in
cast iron vessels without fear of their being attacked, whilst the gain in practice
corresponds to the gain in theory.
The following is the mode of manufacture-To manufacture sodium pyro sulphate,
I introduce 240 Kilos ácid sulphate of sodium or 142 Kilos neutral sodium sulphate
and 98 Kilos. sulphuric acid (hydrate) at 66° B into a cast iron retort provided with
a stirring arrangement.
The retort is connected with an air-pump and heated while exhausting to 260° C;
in the course of from 5 to 8 hours the mass is heated while stirring to 300° to 320° U.
The greater part of the water formed passes off at 260° to 280° C (under a vacuum
of 50 to 60 centimetres of mercury) the temperature being only raised to 320° C to
ensure the completion of the reaction.
The fused mass is then cast in plates and consists of pure sodium pyrosulphate,

page_text: Pyrosulphates of the other alkaline metals as well as of ammonia may be produced
in precisely the same way.
In carrying out this invention it is desirable to introduce between the stirring
vessel and air-pump a condenser and receiver connected by a glass tube so that the
point of completion of the reaction can be readily ascertained, the fusion being
complete as soon as water is no longer to be detected in the glass tube.
Dated this 21st dow of Nana 1007
H. BAUM.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: I, HEINRICH BAUM of Mannheim in the Empire of Germany, do hereby declare
the nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The pyro-sulphuric salts of the metals and especially of the alkali metals (S₂ O, R₁)
have been hitherto obtained either by Berzelius method (vizt. heating the acid or hydro-
sulphates at a brown heat) or by the action of a molecule of SO, upon neutral
sulphates (R. Weber Berlin Berichte vol. 17 page 2498 and H. Schulze page 27056.)
Owing to its expense, the latter method is scarcely practicable for the commercial
production of pyro-sulphates whilst the former method possesses the serious draw-
back that a part of the pyro-sulphate formed at the high temperature of brown heat
almost always decomposes, evolving S. O. Only an inferior product is obtained by
this means when carried out on a large scale added to which, the open cast iron
melting vessels at the high temperature, become very quickly destroyed.
I have discovered that the hydro-sulphates i.e. those of the alkalies and of ammonia
or molecular mixtures of neutral sulphates with H, SO, in vacuo, become converted
at a comparatively low temperature (260° to 320° C) into pyro sulphates and liberate
water without the formation of the slightest trace of S. O,. At these low temperatures,
the operation may be performed in cast iron vessels without fear of their being
attacked whilst the gain in practice corresponds to the gain in theory.
The following is the mode of manufacture. To manufacture sodium pyro-sulphate,
I introduce 240 kilos acid sulphate of sodium or 142 kilos neutral sodium sulphate
and 98 kilos sulphuric acid (hydrate) at 66° B into a cast iron retort provided
with a stirring arrangement. The retort is connected with an air-pump and
heated while exhausting to 260° C; in the course of from 5 to 8 hours, the mass
is heated while stirring, to 300° to 320° C. The greater part of the water formed
passes off at 260° to 280° C (under a vacuum of 50 to 60 centimètres of mercury)
the temperature being only raised to 320° C to ensure the completion of the
reaction. The fused mass is then cast in plates, and consists of pure sodium
pyro-sulphate.
Pyro-sulphates of the other alkali metals, as well as of ammonia, may be produced
in precisely the same way.
In carrying out this invention, it is desirable to introduce between the stirring
vessel and air-pump, a condenser and receiver connected by a glass tube so that the
point of completion of the reaction can be readily ascertained, the fusion being
complete as soon as water is no longer to be detected in the glass tube.

page_text: Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
The production of pyro-sulphates of the alkali metals and of ammonia by heating
the hydrosulphates thereof in vacuo to temperatures below brown heat or between
200° and 400° C. as herein specified.
Dated this 20th day of December 1887.
H. BAUM.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.