Iм- PROVEMENTS IN THE MANUFACTURE OF CHROMATES OF AMMONIA AND CHROMIC ACID, AND IN THE PREPARATION OF NITRATES OF LIME AND BARYTA
Year: 1865

page_text: LETTERS PATENT to William Clark, of 53, Chancery Lane, in the County
of Middlesex, Engineer and Patent Agent, for the Invention of "Iм-
PROVEMENTS IN THE MANUFACTURE OF CHROMATES OF AMMONIA AND CHROMIC
ACID, AND IN THE PREPARATION OF NITRATES OF LIME AND BARYTA."-A
communication from abroad by Félix Debaut, Doctor of Medicine, of
29, Boulevart St. Martin, Paris.
Sealed the 10th April 1866, and dated the 19th October 1865.
PROVISIONAL SPECIFICATION left by the said William Clark at the Office
of the Commissioners of Patents, with his Petition, on the 19th October
1865.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer and Patent Agent, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN THE MANUFACTURE OF CHROMATES OF AMMONIA AND
CHROMIC ACID, AND IN THE PREPARATION OF NITRATES OF LIME AND BARYTA," to
be as follows:-
This improved process is based on the treatment of sulphate and bisulphate
of ammonia by the chromates of lime or of baryta obtained by either of
the following processes:-1st, by treating chromium ore with the nitrates of
lime or baryta, which nitrates themselves, are obtained economically by the
use of acid residues from the manufacture of nitro-benzine. For this purpose
it is sufficient to mix the lime, or baryta, or carbonates of these bases with the
acid residues above mentioned, which latter contain nitric acid, and forming.
by the combination nitrates of lime and baryta, these are then withdrawn in
order to act on the chromium ore. 2ndly, by treating chromium ore with,

page_text: lime, baryta, or their carbonates, with the addition as a flux of chloride of
calcium or any salt of lime sufficiently fusible. 3rdly, treating the chromed
residues from dye works, from electric batteries, or from the manufacture of
aniline by means of lime, baryta, or their carbonates. 4thly, treating hydrated
oxide of chromium by the above-mentioned bases generally, whatever may be
the origin of the said hydrated oxide. The success obtained in these various
processes depends entirely on the temperature, which should not exceed a dark
red heat, the treatment at which temperature I claim as forming part of the
Invention.
First process. I mix intimately the chromium ore with the nitrate of lime
for instance, in equivalent proportions, and carefully raise the pulverulent mass
to a red heat in a reverberatory furnace.
The second process is the same as the foregoing, except that I substitute
carbonates for the nitrates above used.
Third process. I mix the residues together with the base of which it is
desired to make the chromate in such manner that the oxide of chromium
contained in the said residues may be in proportion equivalent with the base.
I spread this mixture on the sole of a reverberatory furnace and heat it
cautiously to redness, which temperature I maintain, care being taken
to stir the pulverulent mass now and then until the oxide of chromium
is almost wholly transformed into chromic acid and combined with the
base.
The fourth process consists in the treatment of hydrated oxide of chromium
generally by means of the bases mentioned in the foregoing processes. I obtain
bydrated oxide of chromium from various sources, or even produce it directly
for such use, by any of the ordinary processes as well understood. In all
cases it will suffice to admix it with the above bases, and raise the temperature
to a red heat for obtaining chromates with the greatest facility.
After the chromate of lime or of baryta has been produced by either of the
above processes I heat them with the sulphate of ammonia if it be desired
to obtain the neuter chromate of ammonia, or with the bisulphate if it is
desired to obtain the bichromate of such base. For this purpose it suffices
to dilute the chromate of lime, for instance in a solution of sulphate or bi-
sulphate of ammonia in equivalent proportions, leaving the materials in contact
for two or three days, and stirring now and then the liquid containing the
chromate, after which the residue is washed and drawn off, and the product
evaporated till sufficiently concentrated for crystallizing the chromate.
The price of chromates obtained by the first process would be too high if
commercial nitric acid were used.. The application to such use of the acid

page_text: residues from the fabrication of nitro-benzine constitutes therefore an industrial
improvement which I claim.
A modification of the processes Two and Three, and which I deem most
important, consists in mixing the residues or the hydrated oxide of chromium
with a half equivalent of potash or soda (or of their carbonates), and in
maintaining the temperature no longer at a red heat, but only at a dark red
heat; with these conditions I obtain bichromate of potash or soda directly,
and which I claim as of this Invention. I also claim the exclusive right of
treating chromates of lime and of baryta in order to obtain chromic acid as
described in the third process of this Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Clark in the Great Seal Patent Office on the 18th
April 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK, of 53, Chancery Lane, in the County of Middlesex, Engineer and
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of October, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Clark, Her special licence that I, the said William Clark, my
executors, administrators, and assigns, or such others as I, the said William
Clark, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF CHROMATES OF AMMONIA AND CHROMIC ACID, AND IN THE PRE-
PARATION OF NITRATES OF LIME AND BABYTA," a communication to me from abroad
by Félix Dehaut, Doctor of Medicine, of 29, Boulevart St. Martin, Paris, upon
the condition (amongst others) that I, the said William Clark, my executors
or administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said.
Totters Patent

page_text: NOW KNOW YE, that I, the said William Clark, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement (that is to say):-
This improved process is based on the treatment of sulphate and bisulphate
of ammonia by the chromates of lime or of baryta obtained by either of the
following processes:-First, by treating chromium ore with the nitrates of lime
or of baryta, which nitrates themselves are obtained economically by the use
of acid residues from the manufacture of nitro-benzine. For this purpose it
is sufficient to mix the lime, or baryta, or carbonates of these bases with the
acid residues above mentioned, which latter contains nitric acid, and forming
by the combination nitrates of lime and baryta, these are then withdrawn in
order to act on the chromium ore. Secondly, by treating chromium ore with
lime, baryta, or their carbonates, with the addition as a flux of chloride of
calcium or any salt of lime sufficiently fusible. Thirdly, treating the chromed
residues from dye works, from electric batteries, or from the manufacture of
aniline by means of lime, baryta, or their carbonates. Fourthly, treating
bydrated oxide of chromium by the above-mentioned bases generally, whatever
may be the origin of said hydrated oxide. The success obtained in these various
processes depends entirely on the temperature, which should not exceed a dark
red heat, the treatment at which temperatures I claim as forming part of the
Invention.
First process. I mix intimately the chromium ore with the nitrate of lime,
for instance, in equivalent proportions, and carefully raise the pulverulent mass
to a red heat in a reverberatory furnace.
The second process is the same as the foregoing, except that I substitute the
bases or their carbonates for the nitrates above used mixed with a fusible salt
of lime.
Third process. I mix the residues together with the base of which it is
desired to make the chromate in such a manner that the oxide of chromium
contained in said residues may be in proportion equivalent with the base. I
spread this mixture on the sole of a reverberatory furnace and heat it
cautiously till redness begins to appear, which temperature I maintain, care
being taken to stir. the pulverulent mass now and then until the oxide of
chromium is almost wholly transformed into chromic acid and combined with
the base.
:
The fourth process consists in the treatment of hydrated oxide of chromium
generally by means of the bases mentioned in the foregoing. I may obtain
bydrated oxide of chromium from various sources, or even produce it directly

page_text: for such use by any of the ordinary processes and as well understood. In all
cases it will suffice to admix it with the above bases and raise the temperature
to a dark red heat for obtaining chromates with the greatest facility.
After the chromates of lime or of baryta have been produced by either of
the above processes I treat them with the sulphate of ammonia if it be desired
to obtain the neuter chromate of ammonia, or with the bisulphate if it is
desired to obtain the bichromate of such base. For this purpose it suffices to
dilute the chromate of lime, for instance in a solution of sulphate or bisulphate
of ammonia in equivalent proportions, leaving the materials in contact for two
or three days and stirring now and then, the liquid containing the chromate
is then drawn off, after which the residue is washed and the product evaporated
till sufficiently concentrated for crystallizing the chromate.
The price of chromates obtained by the first process would be too high if
commercial nitric acid were used. The application to such use of the acid
residues from the fabrication of nitro-benzine or from any other manufacture
constitutes therefore an industrial improvement which I claim.
A modification of the processes Two and Three, and which I deem most
important, consists in mixing the residues or the hydrated oxide of chromium
with a half equivalent of potash or soda (or of their carbonates), and in main-
taining the temperature no longer at a red heat but only at a dark red heat;
with these conditions I obtain bichromate of potash or soda directly. If
an equivalent of the base is mixed the neuter chromate of potash or of soda
are obtained with the greatest facility, and which I claim as of this
Invention.
I also claim the exclusive right of treating chromates of lime and of baryta
obtained by the above processes in order to obtain chromic acid.
In witness whereof, I, the said William Clark, have hereunto set my
hand and seal, this Seventeenth day of April, in the year of our Lord
One thousand eight hundred and sixty-six.
Witness,
53, Chancery Lane,
London.
W. CLARK. (L.S.)