IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS SULPHURIC ACID
Year: 1884

page_text: I, HENRY EDWARD NEWTON of the Office for Patents Bream's Buildings, Chancery
Lane in the County of Middlesex, Civil Engineer do hereby declare the nature of
the invention for IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS SULPHURIC
ACID to be as follows:-
The object of this invention is to produce anhydrous sulphuric acid in a simpler
and more expeditious manner than heretofore, and the invention consists in heating
in a retort monohydrated or highly concentrated sulphuric acid mixed with glacial
phosphoric acid; or by letting vapours of such sulphuric acid pass over a column
of fragments of glacial phosphoric acid. In either case a dehydration of the
sulphuric acid takes place and sulphuric anhydride distils over and may be
condensed in a suitable receiver.
By glacial phosphoric acid is to be understood the monohydrated acid or mixtures
of the mono- and dihydrates thereof.
In carrying out this invention on a large scale an apparatus is used which will
permit of continuous action.
This apparatus it is preferred shall consist of an airtight cylinder of platinum,
stone ware, glass or other acid-proof material, filled with fragments of glacial
phosphoric acid and surrounded with a sand bath which will permit of its being
uniformly heated to the temperature most suitable for the formation of sulphuric
anhydride. On passing vapours of monohydrated or highly concentrated sulphuric
acid through the column of glacial phosphoric acid contained in the aforesaid
cylinder, sulphuric anhydride is formed and distils over, whilst at the same timo
the glacial phosphoric acid absorbs the water contained in the sulphuric acid as
well as a certain quantity of sulphuric acid and liquefies. The liquid part is drawn
off in any convenient manner, and by degrees the glacial phosphoric acid is
consumed, a fresh supply of this material is introduced into the cylinder.
The residual liquid phosphoric acid drawn off contains as above mentioned not
only water but also sulphuric acid which can be distilled off on adding a small
quantity of water. Only dilute phosphoric acid then remains which by the usual
process of evaporation is again converted into phosphoric monohydrate and will
thus serve over and over again.

page_text: I HENRY EDWARD NEWTON of the Office for Patents 6 Bream's Buildings
Chancery Lane in the County of Middlesex, Civil Engineer do hereby declare the
nature of the invention for IMPROVEMENTS IN THE MANUFACTURE OF ANHYDROUS
SULPHURIC ACID and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
The object of this invention is to produce anhydrous sulphuric acid in a simpler
and more expeditious manner than heretofore, and the invention consists in heating
together mixed monohydrated phosphoric acid and highly concentrated sulphuric
acid, or by letting vapours of such sulphuric acid pass over a column of fragments
of monohydrated, commonly called glacial phosphoric acid. In either case a
dehydration of the sulphuric acid takes place and sulphuric anhydride distils over
and is condensed in a suitable receiver.
In order to understand the nature of this improvement it should be clearly
borne in mind that it is not anhydrous phosphoric acid (a very expensive chemical
substance) which is used, but monohydrated or very highly concentrated phosphoric
acid which can be used over and over again by merely evaporating the additional
water taken up in the dehydrating operation above referred to.
In the accompanying drawing I have shown in sectional elevation the apparatus
needed for this manufacture such apparatus being of a very simple character and
capable of being worked continuously.
a is a cylinder of platinum, glass, earthenware or other suitable material capable
of resisting the action of phosphoric as well as of sulphuric acid.
B is a column of fragments of glacial phosphoric acid.
c is a bath of sand or iron filings surrounding the cylinder a which is heated in
any convenient manner and by means of which the glacial phosphoric acid is
maintained at the temperature most suitable for the reaction and which nearly
coincides with the boiling point of monohydrated sulphuric acid.
g is a pipe by which vapours of sulphuric acid are let into the cylinder a These
vapours pass through the column of glacial phosphoric acid contained therein and
the phosphoric acid takes up water and also part of the sulphuric acid and liquefies.
The liquid portion is drawn off through the outlet tube d. On the other hand
fresh glacial phosphoric acid is to be introduced through A which is provided with
a double shutter so as to allow the least possible escape during recharging of the
vapours of sulphuric anhydride wherewith the interior of the cylinder a is filled.
b is a tube through which the vapours of sulphuric anhydride escape into a
suitable condenser, or cooled receiver.
The liquefied phosphoric acid drawn off through the tube d will retain a pro-
portion of sulphuric acid. But on adding a small quantity of water the affinity
between the two acids becomes so much reduced that the sulphuric acid can be
easily distilled over, after which operation only hydrated phosphoric acid remains,
from which by evaporation in the usual manner glacial phosphoric acid is obtained
and which may be applied again to dehydrate a fresh portion of sulphuric acid.
It may be here remarked that it is not absolutely essential that either the
phosphoric or sulphuric acid used should contain no water other than that which

page_text: their monohydrates contain, but inasmuch as the highest concentration gives the
greatest yield it is preferable that the water should not be in excess.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed as communicated to me
by my Foreign Correspondents I declare that what I claim is
In the manufacture of anhydrous sulphuric acid the use of hydrated phosphoric
acid substantially as and for the purpose set forth.