Process of Making Pure Sulphuric Acid and Strong Sulphuric
Year: 1887

page_text: [Communicated from abroad by JOHN BROWN FRANCIS HERRESHOFF, of 135, Clinton
Street, WILLIAM HENRY NICHOLS, of 353, Clinton Avenue, and GEORGE HENRY
NICHOLS, of 253, Clinton Avenue, all in Brooklyn, County of Kings and State of
New York, United States of America.]
Process of Making Pure Sulphuric Acid and Strong Sulphuric
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, 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 :-
This Invention relates to a new process for converting crude sulphuric acid into two
products in one operation namely-First, pure sulphuric acid having the requisite
standard strength of 93.5 per cent; and second, strong but not pure sulphuric acid
having a strength of about 98 per cent hydrated sulphuric acid H, SO..
Reference is to be had to the accompanying drawing forming part of this
Specification.
In carrying the process into effect, sulphuric acid such as is ordinarily produced
is first concentrated up to about 86 per cent H. SO, in a suitable concentrator A.
From this concentrator the said sulphuric acid is conveyed by a pipe a into a vessel B
through which the liquid flows to the discharge pipe b in a tortuous or other course,
the said vessel being meanwhile exposed to heat to such an extent as to further
concentrate the acid it contains to about 95 or 96 per cent H, SO. The acid having
this strength is now carried by the pipe b into a special vessel C through which it runs
in a tortuous or other course to the final discharge pipe d. The vessel C is also
exposed to direct heat, the waste heat then passing under steam boiler D or otherwise
which heat is so regulated as to drive off about one half to two-thirds of the acid
within the vessel in the form of vapor. This vapor is then collected in a suitable

page_text: condenser E, and on condensing it will be found to be sulphuric acid of 93.5 per cent
H, SO, strength (or 66 degrees Baume) of great purity. That portion of the acid in
the vessel which is not distilled is concentrated by the evaporating process to a
strength of about 98 per cent H, SO4, at which strength it leaves the vessel C through
the pipe d. The amount or proportion of pure acid produced from the contents of the
vessel C by distillation depends entirely on the strength of the acid that enters said
vessel through the pipe b. Thus, acid entering the vessel C at a strength of 93.5 per
cent in order to yield a distillate of the same strength would obviously all have to be
distilled. Therefore, it is preferred to feed the acil into the vessel C at a strength of
about 95 to 96 per cent H, SO, which will allow about one-half to be distilled into
pure acid and the remaining half to be concentrated into strong acid.
the
In the ordinary way of concentrating acid up to 97 or 98 per cent H, SO,,
distillates are not carried higher than 75 to 85 per cent H, SO,, and more often only
to 50 or 60 per cent H, SO, the aim being to get the strongest possible acid with the
smallest and weakest possible distillate. All of this weak distillate has to be heated
and distilled again in order to bring it up to a commercial product, and as the total of
acid in these distillates represents only a small percentage of the entire output, the
same is at once mixed with the more impure acid coming from the chambers, and no
attempt made to make from them a purer commercial product. In this process, the
fuel for heating and distilling a second time is saved.
It is regarded as the most important part of the present Invention that by one
continuous process a concentrated product of 98 per cent H, SO, and an extremely
pure acid of 93.5 per cent H, SO, are obtained. Practically, the principal advantage
of the Invention is that one is enabled to make pure acid from substances which have
heretofore only yielded impure acid, and to dispense with the necessity of using the
more expensive methods which thus far have been deemed needful for the production
of a pure acid.
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 process herein described for treating sulphuric acid which has been concentrated
to a strength of about 95 per cent H, SO, or certainly over 93.5 per cent. H, SO₁;
which process consists in evaporating a sufficient quantity of said acid to produce from
the residue strong acid of 98 per cent H, SO, and condensing the vaporised acid
so as to produce a pure acid of 93.5 per cent H, SO4, substantially as hereinbefore
described.
4:
A. MELVILLE CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane London,
Patent Agents.