Year: 1887

page_text: Date of Application, 1st Oct., 1887
Complete Left, 26th June, 1888
Complete Accepted, 27th July, 1888
and I treat the resulting impure acetic acid in the manner hereinafter described, that
is to say I introduce the said impure acid, by means of a pump or otherwise, into
wooden bats or backs (or into vessels adapted to withstand fire or provided with a
steam-jacket) lined with fire-bricks to protect them inside in the manner hereinafter
mentioned. In these vats or other vessels, the said acid is digested for about
forty eight hours at a temperature of about one hundred and twenty degrees (120°)
Fahrenheit with either of the following powerful oxidizing agents, vis-Chromic
Acid, Bichromate of Potash and Sulphuric acid, or Bichromate of Soda and
Sulphuric Acid which oxidize in accordance with the following equations, that
to say-
Bichromate of Potash and Sulphuric Acid :-
K, Cr, O, +4 H, SO₁ = K, SO, + Cr, 3 (SO) + 4 H, 0, +0.

page_text: If vats or backs are used, as above specified, the desired temperature may be
maintained therein by forcing in either wet or superheated, steam.
I then distil the digested acid in steam-jacketted copper stills say of about two
hundred gallons capacity, or in iron stills lined with fire-bricks in the same
manner as the digesting vessels and heated by steam by means of copper coils
therein.
I thus produce a permanent white acetic acid, which can be utilized in the
production of Carbonate of Lead (White Lead) that will be much superior in colour
and otherwise to that made from the acetic acid of commerce (containing resins and
objectionable colouring matter) generally used for this purpose. My improved acetic
acid can also be advantageously utilized in the production of white mass crystal acotato
of lead (English sugar of lead) and in the production of colours such as emerald
green, chrome yellow and the like of superior quality to those heretofore manufactured
from ordinary commercial acetic acid.
The quantity of bichromate or of chromic acid used depends upon the amount of
impurities present in the acetate to be treated. For the treatment of the acid obtained
from one ton of calcium acetate, about twenty five pounds (25 lbs) of bichromate of
potash or of soda and fifty pounds (50 lbs) of sulphuric acid will in most cases be
sufficient, or twolve and a half pounds (12 lbs) of chromic acid. As the latter
contains sulphuric acid free and combined, it is unnecessary to add sulphuric acid
thereto; for this reason, I prefer to use chromic acid.
For the production of pure acetic acid, I again digest and thus further oxidize the
partially purified acetic acid obtained by the process above described, thereby eliminating
therefrom the remaining volatile impurities. For this purpose, I take about one hundred
pounds (100 lbs) of bichromate of potash or of soda and about two hundred pounds
(200 lbs) of sulphuric acid together with one ton of partially purified acid (or any other
convenient quantities can be used in the same or about the same proportions) and I
digest the same in ordinary cast iron stills, say of about two hundred and twenty (220)
gallons capacity, the iron being protected inside from the action of the acid solution
by lining the said stills with bricks as herein described. The contents of the stills
are maintained by fire heat at a temperature of about one hundred and twenty
degrees (120°) Fahrenheit for about twenty four hours; the fire heat is then
increased and the still worked off to dryness. When the distillation commences, a
small portion of the distilled product should be run into a separate receiver and not
employed for the production of pure acid. The further products of distillation are
then to be collected in another receiver. I find it advantageous to employ for this
distillation a condenser made of iron tubes lined with glass; lead condensers will,
however, answer the purpose very well.
The residues or bye-products in the stills consist of a crude chrome alum or about
twenty eight per cent (28%) of sulphate of potash or of soda and about fity one per
cent (51%) of sulphate of sesquioxide of chromium. I recover these byc-products by
reconverting them in the usual or any suitable manner into bichromate of potash
or of soda, which may be again used for the manufacture of acetic acid by my
process.
The acetic acid is now finally distilled with about twenty eight pounds (28 lbs) of
carbonato-of-soda to the ton of acid, in steam copper stills of say one hundred and
twenty (120) gallons capacity which are fed continuously. A pure acid then distils
over. After about thirty hundred-weight (30 cwt) of acid has passed through a still,
it is necessary to clean it out, which is done by opening a stop-cock provided for the
purpose at the bottom of the still, and sluicing the still with water. The acid is
condensed by means of a tin worm, or by other suitable means.
To produce glacial acetic acid, I take the strongest portion obtained from the still
in the distillation last above mentioned, viz. that portion which distils over after
half the quantity contained in the still has distilled over, and I treat it by any well
known or suitable process. By preference, however, I subject it to repeated distil-
lation with concentrated sulphuric acid until acetic acid of one hundred per cent (100%)
is obtained. I treat in this manner only the strong acid which distils over in the latter

page_text: part of the process, and not the weaker acid which distils over during the first part of
the process. The sulphuric acid can be repeatedly utilized in this process by simply
concentrating it after its use in the manner above described. Or it can be employed
in the dilute state for decomposing a fresh quantity of calcium acetate in the initial
process.
Instead of making the impure acid from crude acetates as hereinbefore described,
I can treat the ordinary acetic acid of commerce, according to my invention.
By my process of oxidation with chromic compounds, under the above specified
conditions, I provide for producing at a lower cost than heretofore and by a
continuous operation, a technically white and pure acetic acid from the lowest quality
of calcium acetate (by reason of the small quantity of reagents required), and for the
recovery of the reagents used.
The wood vats and backs which I employ are preferably of about eight hundred
(800) gallons capacity and provided with wood covers. Any other size and
description of vessel will, however, answer my purpose with greater or less advantage
provided it is protected as herein described. For lining the said vessels, I use fire-
bricks about half an inch thick firmly cemented to the inside of the vessel by means
of a cement composed of a solution of silicate of soda and pure silica oxide (in a fine
powder) which, when mixed with the silicate of soda solution is of the consistency of
ordinary brickmaker's mortar.
The bricks are firmly grouted in with this mixture, and the surface is then plastered
over with the same. This surface, when dry, is not affected in digesting the acetic
acid in the manner above described.
By lining the vessels as above described, I greatly reduce the expenditure for
plant, chromates mixed with sulphuric acid being of well known destructivo
character.
I do not confine myself to the exact proportions above stated, as, in either of the
processes herein described, the proportions may be varied without materially affecting
the results obtained.
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: Na, Cr. O, + H₂ SO₁
=
2 (Cr 0₂) + Na, SO, + H, O.
If vats or backs are used as above specified, the desired temperature may be
maintained therein by forcing in either wet or superheated steam.
When the digested liquor shows no precipitate of yellow chromate of lead on testing 3
with acetate of lead, it is then distilled in steam-jacketed copper stills, say of about
two hundred gallons capacity, or in iron stills lined with fire-bricks in the
same manner as the digesting vessels, and heated by means of copper steam-coils
therein.
I prefer to adopt the latter method as it is much less costly than the former.
3

page_text: I thus produce a permanent white acetic acid adapted for the production of
carbonate of lead (white lead), which when manufactured from my improved acetic acid,
is much superior in colour and otherwise to that mado from the ordinary acetic acid of
commerce generally used for this purpose, which contains resins and objectionable
colouring matter in large quantities. My improved acetic acid is also adapted for the
production of white acetate of lead (English sugar of lead) and of acetate of soda
crystals from which pure acetic acid is usually made, and also of colours such as
emerald green, chrome yellow and the like of superior quality to those herotoforo
manufactured from ordinary commercial acetic acid.
The quantity or proportion of bichromate or of chromic acid used in the process
above described depends upon the amount of impurities present in the acetate from
which the acetic acid to be treated is obtained. For the treatment of the acid obtained
from one ton of calcium acetate, about twenty five pounds (25 lbs) of bichromate of
potash or bichromate of soda together with twelve and a half pounds (12 lbs)
of sulphuric acid of 80% will generally be sufficient, or about twelve and a half
pounds (12 lbs) of chromic acid. As the latter contains sulphuric acid free and
combined, it is unnecessary to add sulphuric acid thereto; for this reason I prefer to
use chromic acid in this part of my process.
For the production of pure acetic acid I again digest and thus further oxidize, the
partially purified acetic acid obtained by the process above described, thereby
eliminating therefrom the remaining volatile impurities. For this purpose I take
about one hundred pounds (100 lbs) of bichromate of potash or bichromate of soda
and about two hundred pounds (200 lbs) of sulphuric acid of 100% together with
one ton of partially purified acid (or other convenient quantities in, or about in, these
proportions), and I digest the same in ordinary cast iron stills say of about two
hundred and twenty (220) gallons capacity, the iron being protected inside from the
action of the acid solution by lining the said stills with bricks as hereinafter described.
The contents of the stills are maintained by fire heat at a temperature of about one
hundred and twenty degrees (120°) Fahrenheit for about twenty four hours; the fire
hoat is then increased to the point at which distillation takes place and tho still
worked off to dryness.
The following equations will serve to indicate the reactions which take place in the
decomposition of the bichromate effecting oxidation of tho acetic acid.
1. Shewing formation of chromic acid.
K, Cr, O, + H, SO₁ = 2 (Cr O₂) + K₂ SO + H₂ O
or Na. Cr. O. + H. SO. = 2 (Cr O.) + Na. SO. + B. O.
2. Shewing liberation of oxygen :-
2 (Cr O₂) + K, SO, + 3 H₂SO, + H₂O = Cr₂ (SO)3 + K, SO₁ + U₁₂ + 4 H₂O
or 2 (Cr O₂) + Na, SO, + 3 H, SO, + H2O = Cr, (SO₁)3 + Na, SO. + 0, + ± H₂ O.
When the distillation commences ("heading the still ") a small quantity of thic
distilled product (about ten gallons, more or less according to circumstances) and a
similar quantity at the end of the distillation (the "tailings") should be run into
a separate receiver and not employed for pure acetic acid. The further products of
distillation are collected in another receiver. I find it advantageous to employ for
this distillation a condenser made of iron tubes lined with glass lead condensers will
however answer the purpose very well. The headings and tailings of the stills are
used over again in the first oxidation or employed for any purpose .where ordinary
common acetic acid is required.
The residues or bye-products in the stills consist of a crude chrome alum or about
twenty eight per cent (28%) of sulphate of potash or sulphate of soda and about
fifty one per cent (51%) of sulphate of sesquioxide of chromium. I reconvert these
bye-products in the usual or any suitable manner, into bichromate of potash or
bichromate of soda, which may be again used for the manufacture of acetic acid by
uy process.

page_text: The acetic acid is now finally distilled with about twenty eight pounds (28 lbs) of
carbonate of soda to the ton of acid in steam copper stills or in iron stills lined with
fire-bricks and having a copper steam-coil therein as above described, the said stills
being of say one hundred and twenty (120) gallons, capacity. The first portion
(about two gallons) which distils over should be kept apart as it contains volatile
ethers. A pure acid then distils over, the still is worked off and repeatedly charged
and worked as described till about thirty hundred weight (30 cwt) of acid has passed
through the still, it is then necessary to clean it out, which is done by opening a stop-
cock provided for the purpose at the bottom of the still, and sluicing the still with
water. The acid is condensed by means of a tin worm or by other suitable means.
Larger or smaller stills may be used and the stills may be advantageously and more
economically worked in vacuo.
To produce glacial acetic acid, I tako the strongest portion obtained from the
still in the distillation last above mentioned, viz-that portion which distils over
after half the quantity contained in the still has distilled over, and I treat it by any
well known or suitable process. By preference, however, 1 subject it to repeated
distillation with concentrated sulphuric acid until acetic acid of one hundred per
cent (100%) is obtained. I treat in this manner only the strong acid which distils
over in the latter part of the process and not the weaker acid which distils over
during the first part of the process. The sulphuric acid can be repeatedly utilized
in this process by simply concentrating it after its use in the manner above
described. Or it can be employed in the dilute state for decomposing a fresh
quantity of calcium acetate in the initial process.
Instead of making the impure acid from crude acetates as hereinbefore described,
I can treat the ordinary acetic acid of commerce according to my invention.
By my process of oxidation with chromic compounds under the above specified
conditions, I provide for producing at a lower cost than heretofore and by a con-
tinuous operation, a technically white and pure acetic acid from the lowest quality of
calcium acetate and for the recovery of the reagents used.
The wood vats and backs which I employ for digesting are preferably of about
eight hundred (800) gallons capacity and provided with wood covers. Any other size
and description of vessel will, however, answer my purpose with greater or less
advantage provided it is protected as hereinafter described.
For lining the vats, backs, iron stills or other vessels employed in my process, I
use fire-bricks preferably of about half an inch thick firmly cemented to the inside
of the vessel by means of a cement composed of a solution of silicate of soda and
pure silica oxide (in a fine powder) which, when mixed with the silicate of soda
solution, is of the consistency of ordinary bricklayer's mortar, and resists the action
of the acids or is not attacked thereby.
The bricks are firmly grouted in with this mixture and the surface is then plastered
over with the same. The surface thus formed is dried, and is then not liable to be
affected in the above described process of digesting or distilling the acetic acid.
By lining the vessels in this manner I greatly reduce the oxpenditure for plant,
chromic compounds being of well-known destructive character.
I do not confine myself to the exact proportions above stated, as in either of the
processes.herein.described the proportions may be varied without materially affecting
the results obtained.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I wish it understood that
I claim -
First. In the manufacture of acetic acid, the. use of chromic acid, or of a chromate
together with sulphuric acid for oxidizing the impure acetic acid, as above specified.
Second. The manufacture of pure acetic acid by first decomposing crude calciuni
acetate, then treating the resulting impure acetic acid with chromic acid or with a
chromate together with sulphuric acid and then digesting and further oxidizing the
partially purified acid, substantially as set forth.

page_text: Third. The improved method or process of producing glacial acetic acid by repeated
distillation with concentrated sulphuric acid, as above specified.
Fourth. The recovery of the reagents used in my improved process, substantially
as set forth.
Fifth. The improved acetic acid manufactured substantially as hereinbefore described.
Sixth. A vat, back, still or other vessel lined with fire-bricks secured by means of
cement consisting of a solution of silicate of soda and pure silica oxide, substantially
as, and for the purpose, set forth.