MANUFACTURING CHROMATE.
Year: 1852

page_text: LETTERS PATENT to James Curtis Bonth, of the City and County
of Philadelphia, in the State of Pennsylvania, United States of
America, Chemist, for the Invention of "MANUFACTURING CHROMATE.
PROVISIONAL SPECIFICATION left by the said James Curtis Booth
at the Office of the Commissioners of Patents, with his Petition,
on the 9th November 1852.
I, JAMES C. BoOTI, do hereby declare the nature of the said Inven-
tion for "MANUFACTURING CHROMATE AND BICHROMATE OF POTASH PROM
CHROMIC IRON OR CHROME ORE" to be as follows:-
The ordinary mode of obtaining chromate and bichromate of potash
from chrome ore is by the repeated heating of the chrome ore together
with carbonate of potash; sometimes saltpetre is added, but the opera-
tion may be effected without saltpetre.
The nature of my Invention consists in reducing the oxide of iron in
chrome ore, either wholly or in part, by means of carbon in any of its
several forms, or by means of any of its compounds, which are or may

page_text: be employed as fuel, such as carbonic oxide, carburetted hydrogen, as
the first stage of the manufacture. And secondly, in removing the
iron so reduced by means of sulphuric acid. The remainder of the
process of manufacture is similar to that at present in use. That is,
I heat the residue obtained by my improved process in contact with
carbonate of potash, and either with or without saltpetre.
In carrying out this Invention I take the ore known as chromic iron
or chrome ore, and grind it to a powder by the usual mechanical means.
I mix the powdered ore with about one fifth of its weight of powdered
charcoal, or other suitable carbonaceous matter. This mixture is
placed upon the hearth of a reverberatory furnace, constructed as the
reverberatory furnaces for reheating or puddling iron are ordinarily
constructed, that is, so that the heat or flame may be as free as prac-
ticable from free oxygen or atmospheric air. By this operation the
greater part or all of the oxide of iron in the chrome ore is reduced to
the metallic state. When one charge of the mixture is reduced as above
described it is raked out, and a second charge of the mixture introduced
into the heated furnace, reduced and replaced by a third, and so on.
Each charge when raked out of the furnace is thrown into dilute sul-
phuric acid, contained in vats, whereby the iron is dissolved, forming a
solution of proto-sulphate of iron or copperas. This solution, still con-
taining free acid, is drawn off, and run upon a fresh charge of reduced
ore, in order more fully to saturate the free acid, after which it is again
drawn off, and evaporated to crystallization, so as to produce copperas
in a state adapted to commerce. The residue in the vats is well washed
with water, and dried; it is then mixed with carbonate of potash, or
with carbonate of potash and saltpetre, and heated in the same manner
that the chrome ore itself is in the first instance heated in the process
usually employed and described above.
The solution obtained by washing the residue of the ore after the
sulphate of iron is produced may be again economically used for
diluting the acid, which is to be applied to remove another portion of
iron from a succeeding charge.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Curtis Both in the Great Seal Patent
Office on the 9th May 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
JAMES CURTIS BOотH, of the City and County of Philadelphia, in the
State of Pennsylvania, United States of America, Chemist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of November, in the year
of our Lord One thousand eight hundred and fifty-two, in the sixteenth
year of Her reign, did, for Herself, Ier heirs and successors, give and
grant unto me, the said James Curtis Booth, Her special license that
I, the said James Curtis Booth, my executors, administrators, and
assigns, or such others as I, the said James Curtis Booth, 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 "MANUFACTURING
CHROMATE AND BICHROMATE OF POTASH FROM CHROMIC IRON OR CHROME
ORE," upon the condition (amongst others) that I, the said James Curtis
Booth, by an instrument in writing under my hand and seal, 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 Letters Patent.
.
NOW KNOW YE, that I, the said James Curtis Booth, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement (that is to say):
The ordinary mode of obtaining chromate and bichromate of potash
from chrome ore is by repeatedly heating chrome ore in the presence
of carbonate of potash. Sometimes saltpetre is added, but the opera-
tion is frequently carried on without saltpetre. Chrome ore is composed
chiefly of oxide of chrome and oxide of iron, and the chemical reaction

page_text: which takes place during the operation of heating the ingredients is
well known. The oxide of chrome contained in the chrome ore is
peroxydized, and converted into chromic acid, and this chromic acid
combines with the potash in the carbonate of potash, thereby forming
chromate of potash, while carbonic acid is liberated. The oxide of iron
and the chromate of potash are then separated by lixiviation. This
process of making chromate of potash requires that the ore should be
heated several times in succession with fresh portions of carbonate of
potash, for a portion only of the oxide of chrome is oxydized and
separated from the ore at a single heating.
The nature of the present Invention consists in reducing the oxide
of iron in chromic ore, either wholly or in part, by means of carbon in
any of its several forms, or by means of any of its compounds, which
are or may be employed as fuel, such as carbonic oxide, carburetted
hydrogen. This operation forms the first stage of the manufacture.
The second operation consists in removing by means of sulphuric acid
the iron that has been reduced by the first part of the process. The
remainder of the process of manufacture is similar to that which has
been described above as being now in use, namely, to heat the residue
obtained by my improved process in contact with carbonate of potash,
and either with or without saltpetre.
To enable others skilled in the art to carry out my Invention I will
describe more minutely the mode of applying my improvement, which
I have found to answer best. I do not, however, intend to limit myself
to the peculiar proportions of acid specified, or form or proportions of
carbon. I take the ore known as chromic iron or chrome ore, and grind
it to a powder by the usual mechanical means. I then mix the powdered
ore with about one fifth of its weight of powdered charcoal. This mix-
ture is placed upon the hearth of a reverberatory furnace, constructed as
the reverberatory furnaces for reheating or puddling iron are ordinarily
constructed, (that is to say,) in such a manner that the heat or flame
may be as free as practicable from uncombined oxygen or atmospheric
air. By this operation the greater part or all of the oxide of iron in
the chrome ore will be decomposed, and the iron reduced to the metallic
state. When one charge of the mixture has been reduced as above s
described it is to be raked out, and a second charge of the mixture

page_text: must be introduced into the heated furnace, reduced in its turn, and
replaced by a third charge, and so on. Each charge when raked out
of the furnace is to be thrown into vats containing dilute sulphuric
acid, whereby the iron is dissolved, and a solution of proto-sulphate of
iron or copperas is thereby formed. This solution (still containing free
acid) is to be drawn off, and run upon a fresh charge of reduced ore.
in order more fully to saturate the free acid, after which it is again to be
drawn off, and evaporated to crystallization, so as to produce copperas
in a state adapted for commerce. The residue in the vats is then to be
well washed with water, and dried, and afterwards mixed with carbonate
of potash, or with carbonate of potash and saltpetre, and heated in the
same manner that the chrome ore itself has been in the first instance
heated in the process usually employed and described above.
The following are the advantages of my improved process :-By the
ordinary method of manufacturing chromate and bichromate of potash
only a portion of the oxide of chrome is oxydized, and consequently
only a portion of the materials are converted into chromate of potash
by a single heating; it will therefore be seen that repeated heatings
with fresh portions of potash will be required to complete the process.
These repeated heatings with potash involve a considerable. loss of
potash by volatilization; but by the employment of my improved process
the first heating with carbonate of potash converts all or nearly all the
oxide of chrome into chromate of potash, and thus much of this loss by
volatilization of the potash is avoided. The production of copperas,
incidental to the improved process, also assists in defraying the expense
involved in carrying out the improvements. The quantity of oil of
vitriol I employ is nearly equal in weight to about two thirds of the
weight of the ore itself.
The process precisely as above-described experiment has led me to
believe to be the most effective and economical, but I do not desire to
limit myself to the precise substances or proportions thereof, or to the
precise kind of furnace to be employed for heating the materials; for
instance, instead of powdered charcoal as specified above, coke, anthra-
cite, or bituminous coal, or any other carbonaceous fuel or carbonaceous
materials
may be used, and, instead of a reverberatory or other furnace,
gas retorts may be used.

page_text: The solution obtained by washing the residue of the ore after the
sulphate of iron has been produced may be again economically used
for diluting the acid, which is to be applied to remove another portion
of iron from a succeeding charge.
Having now described my Invention, and the best means with which
I am at present acquainted for carrying out my improvements, I would
observe, in conclusion, that I do not desire or intend to claim separately
as my Invention such portion of the process herein-before described as
I have stated to be similar to that now in use for manufacturing chro-
mate and bichromate of potash; but what I do desire to claim as my
Invention, and to secure by Letters Patent, is,―
First, the employment of carbonaceous materials in the reduction
of chrome ore, as herein described, as a stage in the manufacture of
chromate of potash.
Secondly, the art or process of manufacturing chromate and bichro-
mate of potash from chromic iron ore by means of the reduction of
the oxide of iron, and the removal of the reduced iron by the usual sub-
stances and modes, substantially as are herein enumerated and set forth.
Thirdly, the process of reduction and removal herein described in
connection with the old process of reduction herein described, or in
combination with any equivalent therefor.
In witness whercof, I, the said James Curtis Booth, have here-
unto set my hand and seal, this Twenty-third day of February,
in the year of our Lord One thousand eight hundred and
JAS C. BOOTH. (LS.)
Taken and acknowledged by James Curtis Booth
(party hereto) at Her Britannic Majesty's Consulate
iu Philadelphia on the day above written, before me,
(L.S.) ROBERT BUNCH,
Her Brit. Maj's Acting Consul for the
Stain D...