IMPROVEMENTS IN OR APPERTAINING TO THE CONCENTRATION OR PURIFICATION OF COMMERCIAL SULPHURIC ACID
Year: 1883

page_text: LETTERS PATENT to William Jones Menzies of St Helens in the county of
Lancaster for an Invention of "IMPROVEMENTS IN OR APPERTAINING TO THE
CONCENTRATION OR PURIFICATION OF COMMERCIAL SULPHURIC ACID
"
PROVISIONAL SPECIFICATION left by the said William Jones Menzies at the
Office of the Commissioners of Patents on the 29th June 1883.
OF
WILLIAM JONES MENZIES of St Helens in the County of Lancaster IMPROVE-
MENTS IN OR APPERTAINING TO THE CONCENTRATION OR PURIFICATION
COMMERCIAL SULPHURIC ACID."
Commercial vitriol, generally made from pyrites, contains many impurities such
as arsenic, iron, and traces of lend, which unfit it for many purposes for which a
fine sulphuric acid is required in the arts and manufactures. Pyrites vitriol is
also unfitted for concentration in the usual platinum or glass stills, owing to the
scale gradually formed on the inner surface in the case of the platinum still, causing
the platinum to be destroyed and burnt by the fire, or in the case of glass stills
causing them to crack.
I have discovered that a pure bydrated Sulphuric acid, that is to say some three
or four per cent stronger than the ordinary 66 Baumé acid of commerce, can be
obtained by distilling the ordinary pyrites vitriol as obtained from the Glover
towers, in an iron vessel or still, connected with a suitable condensing apparatus,
preferably a range of thin glass pipes, in which the fumes of hydrated sulphuric
acid passing over from the still are condensed, and a puro hydrated sulphuric acid
thus obtained. It is necessary that the acid should be of a concentration not less
than that usually coming from Glover towers, that is to say not less than
58 Baumé, and also that the arsenic shall exist in the form of arsenic acid, which
is generally the case with commercial vitriol after passing through Glover towers,
owing to the action of the nitric acid in the nitrous vitriol when passing through
the Glover tower in the usual manner. If the vitriol to be purified and con-
centrated by distillation has not been passed through a Glover tower but is simply
chamber acid, it must previously be concentrated in leaden pans, with afterwards
a small addition of nitric acid, or some other oxidising agent so as to convert all
the arsenic existing in the form of arsenious acid into arsenic acid. If acid of a
less strength than 58 Baumó is used, there is some action on the top of the iron
still and unless the arsenic is completely oxidised into arsenic acid, it will pass
over with the fumes of hydrated sulphuric acid, instead of being left behind as an
insoluble deposit at the bottom of the still. If vitriol however of a degree of

page_text: concentration of not less than 58 Baumé be used, there is no action at all on the
iron still below the surface of the boiling acid, and only a very slight action on the
top of the still, when the first portions of water contained in the commercial
vitriol pass off together with some sulphuric acid, the action ceasing entirely as
soon as the last traces of water have passed away.
I am aware that it has been proposed to distil over commercial vitriol so as to
obtain a sulphuric acid free from impurities, but nobody has proposed to do this in
iron vessels. I am also aware that it has been proposed to obtain a concentrated
sulphuric acid by heating in iron vessels a paste formed of a mixture of sulphate
of lead, sand, or gypsum, with chamber acid, that is to say a weak acid of about
50 Baumé, but nobody has proposed to distil an impure commercial vitriol of a
strength of not less than 58 Baumé alone in an iron vessel, the arsenic it contains
being fully oxidised for the purpose of obtaining a highly concentrated sulphuric
acid and also free from all inipurities.
The following is a description of the plan of working I propose to adopt.
An iron kettle with straight sides, the metal varying in thickness from two
inches at the top where there is the greatest wear and tear, down to one inch at
the bottom, has a movable iron top two inches thick fastened onto the kettle with
a tight joint. An iron elbow pipe is either fastened to the top or forms part of it
and arranged at such an angle that any condensation taking place in it can run
back into the iron still. A small inner flange is placed at the end of the pipe to
completely arrest any condensation of acid in the iron elbow pipe being carried
forward. The cooling and condensing range is constructed preferably of thin
taper glass pipes, such as are now extremely used for condensing muriatic acid,
fitted into each other and set at a slight inclination, so that the fumes of hydrated
sulphuric acid as condensed shall flow down them and through the draw off pipo
to the cisterns. A leaden tower filled with flints, glazed bricks, or some other
equivalent substance not acted upon by sulphuric acid, condenses the last traces of
escaping sulphuric acid, and through this a small stream of water may be passed
the better to effect this object by cooling and condensing these sulphuric acid
fumes.
The still is provided with a feed pipe and manhole for cleaning out or removing
from time to time the deposit of arsenic, iron, and other impurities which collect at
the bottom of the iron still. A heating flue from the fire place is so arranged that
neither the bottom nor top of the still are exposed to the direct heat of the fire.
In working the apparatus described above, the still is first filled nearly to the
top with vitriol, preferably coming hot from the Glover tower and the fire is
brought to bear upon it. At first sulphuric acid with steam passes off forming
weak acid, which can for the most part be drawn off into the cistern, or the wholo
of it allowed to run into the bottom of the condensing tower. As soon as the last
traces of steam have passed away, pure hydrated sulphuric acid begins to distil
over, and is almost immediately condensed in the row of glass pipes. This acid is
drawn off into the lend cistern which can be cooled if necessary by a coil of lead
pipe with water running through it; this operation proceeds until the acid is
distilled away down to the point immediately above the fire flue. The still is
then refilled with acid by the feed pipe, and the operation commenced again and
carried on continuously until a large accumulation of arsenic, iron, and other
impurities collect at the bottom of the still, which can then be removed through
the manhole either completely or the chief part of them by fishing them up with
an iron scoop.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Jones Menzies in the Great Seal Patent Office on the
29th December 1883.
WILLIAM JONES MENZIES of St Helens in the county of Lancaster "IMPROVE.
MENTS IN OR APPERTAINING TO THE CONCENTRATION OR PURIFICATION OF
COMMERCIAL SULPHURIC ACID "
Commercial vitriol, generally made from pyrites, contains many impurities such
as arsenic, iron, and traces of lead, which unfit it for many purposes for which a
fine sulphuric acid is required in the arts and manufactures. Pyrites vitriol is
also unfitted for concentration in the usual platinum or glass stills, owing to the
scale gradually formed on the inner surface in the case of the platinum still,
causing the platinum to be destroyed and burnt by the fire, or in the case of glass
stills causing them to crack.
I have discovered that a pure hydrated sulphuric acid, that is to say some three
or four per cent stronger than the ordinary 66 Baumé acid of commerce, can be
obtained by distilling the ordinary Pyrites vitriol as obtained from the Glover
towers, in an iron vessel or still connected with a suitable condensing apparatus,
preferably a range of thin glass pipes, in which the fumes of hydrated sulphuric
neid passing over from the still aro condensed, and a pure hydrated sulphuric acid
thus obtained. It is necessary that the acid should be of a concentration not less
than that usually coming from Glover towers, that is to say not less than 58 Baumé,
and also that the arsenic shall exist in the form of arsenic acid, which is generally
the case with commercial vitriol after passing through Glover towers, owing to the
action of the nitric acid in the nitrous vitriol when passing through the Glover
tower in the usual manner. If the vitriol to be purified and concentrated, by
distillation has not been passed through a Glover tower but is simply chamber
acid, it must previously be concentrated in leaden pans, with afterwards a small
addition of nitric acid, or some other oxidising agent, so as to convert all tho
arsenic existing in the form of arsenious acid into arsenic acid. If acid of a less
strength than 58 Baumé is used, there is some action on the top of the iron still,
and unless the arsenic is completely oxidised into arsenic acid, it will pass over
with the fumes of hydrated sulphuric acid, instead of being left behind as an
insoluble deposit at the bottom of the still. If vitriol however of a degree of
concentration of not less than 58 Baumé be used there is no action at all on tho
iron still below the surface of the boiling acid, and only a very slight action on
the top of the still, when the first portions of water contained in the commercial
vitriol pass off together with some sulphuric acid, the action ceasing entirely as
soon as the last traces of water have passed away.
I am aware that it has been proposed to distil over commercial vitriol so as to
obtain a sulphuric acid free from impurities, but nobody has proposed to do this
in iron vessels. I am also aware that it has been proposed to obtain a concentrated
sulphuric acid by heating in iron vessels a paste formed of a mixture of sulphato
of lead, sand, or gypsum, with chamber acid, that is to say a weak acid of about
50 Baumé, but nobody has proposed to distil an impure commercial vitriol of a
strength of not less than 58 Baumé alone in an iron vessel, the arsenic it contains
being fully oxidised for the purpose of obtaining a highly concentrated sulphuric
acid and also free from all impurities.
The following is a description of the plan of working I propose to adopt.
An iron kettle with straight sides, the metal varying in thickness from two

page_text: inches at the top where there is the greatest wear and tear, down to one inch at
the bottom, has a movable iron top two inches thick fastened onto the kettle with
a tight joint. An iron elbow pipe is either fastened to the top or forms part of it
and arranged at such an angle that any condensation taking place in it can run
back into the iron still. A small inner flange is placed at the end of the pipe to
completely arrest any condensation of acid in the iron elbow pipe being carried
forward. The cooling and condensing range is constructed preferably of thin
taper glass pipes, such as are now extensively used for condensing muriatic acid,
fitted into each other and set at a slight inclination, so that the fumes of hydrated
'sulphuric acid as condensed shall flow down them and through the draw-off pipe
to the cisterns. A leaden tower filled with flints, glazed bricks, or some other
equivalent substance not acted upon by sulphuric acid condenses the last traces of
escaping sulphuric acid, and through this a small stream of water may be passed
the better to effect this object by cooling and condensing these sulphuric acid
fumes.
The still is provided with a feed pipe and man-hole for cleaning out or removing
from time to time the deposit of arsenic, iron, and other impurities which collect
at the bottom of the iron still. A heating fluo from the fire place is so arranged
that neither the bottom or top of tho still are exposed to the direct heat of
the fire.
In working the apparatus described above, the still is first filled nearly to the
top with vitriol, preferably coming hot from the Glover tower, and the fire is
brought to bear upon it. At first sulphuric acid with steam passes off forming
weak acid, which can for the most part be drawn off into the cistern, or the whole
of it allowed to run into the bottom of the condensing tower. As soon as the
last traces of steam have passed away, pure hydrated sulphuric acid begins to
distil over, and is almost immediately condensed in the row of glass pipes. This
acid is drawn off into the lead cistern which can be cooled if necessary by a coil
of lead pipe with water running through it; this operation proceeds until the
acid is distilled away down to the point immediately above the fire flue. The still is
then refilled with acid by the feed pipe, and the operation commenced again and
carried on continuously until a large accumulation of arsenic, iron, and other
impurities collect at the bottom of the still, which can then be removed through
the man-hole either completely or the chief part of them by fishing them up with
an iron scoop.
It is obvious from the above description that the principles upon which I work
are as follows. By thoroughly oxidizing the arsenious acid and ferrous sulphate
in the sulphuric acid, and heating the latter to distillation point, the arsenic and
iron become insoluble in the concentrated hot acid and are precipitated in the pan
or still, while the acid is distilled off-the acid remaining in the still, after
distillation has proceeded a short time, if withdrawn from the still without
withdrawing the sediment, will be found practically free from iron and arsenic,
and it will probably be found eventually the best plan to proceed on these lines,
namely, fully oxidize the arsenic and the iron salts in the acid by means of nitric
acid, boil or distil off a portion of the liquor in an iron still or boiler till the
maximum strength of acid is attained, then let the precipitate settle and decant
off the hot nacid.
Having now described my invention and the best mode known to me of carrying
it into effect, I wish it to be understood that what I believe to be new and desiro
to protect by Letters Patent is :-
ist. The concentration or purification of commercial sulphuric acid by treating
it with nitric acid or other oxidizing agent so as to fully oxidize the arsenic and
iron salts, and then precipitating the latter by boiling in an iron vessel, the acid
to be concentrated in this manner not being of lesser strength than 58 Baumé
for the reasons described.

page_text: 2nd. In combination with the above, continuing the boiling and condensing
the fumes as pure hydrated sulphuric acid.
In witness whereof I the said William Jones Menzies have hereunto set my
hand and seal this twenty eighth day of December in the year of our Lord one
thousand eight hundred and eighty three.
BUTT TTIT TANTS NZIES
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