IMPROVEMENTS IN THE MANU- FACTURE OF WHITE PIGMENTS, ALKALIES AND ALKALINE SUBSTANCES
Year: 1882

page_text: "
LETTERS PATENT to Carl Friedrich Claus, of Mark Lane, in the City of
London, Chemist, for an Invention of IMPROVEMENTS IN THE MANU-
FACTURE OF WHITE PIGMENTS, ALKALIES AND ALKALINE SUBSTANCES."
PROVISIONAL SPECIFICATION left by the said Carl Friedrich Claus at the
Office of the Commissioners of Patents on the 28th August 1882.
CARL FRIEDRICH CLAUS, of Mark Lane, in the City of London, Chemist,
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE PIGMENTS, ALKALIES, AND
ALKALINE SUBSTANCES
"
The first part of my Invention consists in a new process for the production of a
white pigment, and is carried into practice as follows; that is to say, I dissolve
finely ground uncalcined calamine in caustic ammonia, and after having separated,
by filtration, the clear solution from the insoluble residuum, I precipitate the zinc
from the ammoniacal solution by means of solutions of sulphides of alkalies or of
the sulphides of alkaline earths.
When the sulphides, including the bisulphides or hydro sulphides of calcium,
barium, or strontium have been used as precipitants, I obtain a precipitate consisting
of sulphide of zinc and carbonate of lime, of baryta, or of strontia. The ammonia
which has been used as the solvent for the zinc remains in solution. This
ammonia, which I recover and use repeatedly, I separate from the precipitate by
filtration or distillation, or by both these operations. The precipitate I first dry,
and then I heat the same, out of contact with air, to a red heat, in retorts or muffle
furnaces. After heating it, I withdraw the same from the retorts or muffles and
cool it either out of contact with air or by plunging the same into water. When
cool, I grind and levigate the same to form the pigment above mentioned.
When sulphide of ammonium has been used as the precipitant for the zin, the
precipitate consists of sulphide of zinc only, while the carbonate of ammonia, and
tle caustic ammonia which has been used as a solvent for the zinc, remain in
solution. I separate the carbonate of ammonia and the caustic ammonia from the
sulphide of zinc precipitate, by distillation. I treat the precipitate of sulphide of
zinc as above described with reference to the mixed precipitate.

page_text: When sulphide of potassium, or of sodium, has been used for precipitating the
zine from the ammoniacal solution, the precipitate consists of sulphide of zinc,
carbonate of potassa, or carbonate of soda being in the solution in addition to the
caustic ammonia which has acted as the solvent for the zinc. I separate the
ammonia by distillation, and I separate the carbonate of potassa, or of soda, from
the precipitate, by filtration. I boil down the filtrate to form commercial carbonate
of potassa or of soda. The sulphide of zinc I treat as above described. I produce
the precipitants, that is to say, the sulphide of potassium or of sodium for the above
purpose, by decomposing their sulphates by sulphide of barium or of strontium.
The sulphates of baryta or of strontia I may mix in suitable proportions with the
precipitate of sulphide of zinc. Or I add the sulphates of potassa or of soda in
solution to the solution of zinc in ammonia, and precipitate the mixture by the aid
of sulphide of barium or of strontium when a mixed precipitate of sulphide of
zine and sulphate of baryta or sulphate of strontia is formed, and carbonate of
potassa or soda remains in solution
According to the second part of my Invention I dissolve oxide of zinc either in
solutions of carbonate of ammonia or in mixtures of carbonate of ammonia and
caustic ammonia, and precipitate the zinc from this solution by means of solutions
of sulphide of potassium, or of sodium, or of ammonium, or by solutions of the
sulphide of barium or of strontium.
When carbonate of ammonia has been used as a solvent for the zinc, and a
sulphide of an alkali has been employed as a precipitant I obtain a precipitate of
sulphide of zinc, and the carbonate of the respective alkali, together with caustic
ammonia, are in solution whilst, when the sulphide of barium or sulphide of
strontium has been used as a precipitant, the precipitate consists of sulphide of
zinc mixed with carbonate of baryta or of strontia, both of which are insoluble,
caustic ammonia only being in the solution.
When mixtures of carbonate of ammonia and caustic ammonia have been use
as solvents for zinc and I use sulphide of barium or of strontium as precipitants,
I obtain, besides the carbonate of baryta or of strontia, also a quantity of hydrate
of baryta or of strontia, which is to be found in solution together with the caustic
ammonia. This hydrate of baryta or of strontia I obtain from the said solution.
By the presence of carbonate of ammonia in the dissolving liquid a larger quantity
of zinc is dissolved in the ammonia than would be practicable without this
carbonate but the presence of the carbonic acid lessens the yield of hydrate of
strontia or of baryta. To remove a part of the carbonic acid from the solution of
zinc I add some cream of lime, and separate the carbonate of lime formed from the
solution before adding the sulphide of barium or of strontium.
Thirdly. In a Specification of a Patent granted to me in 1878 No 3246 for the
manufacture of sulphide of zinc I stated that I dissolve the zinc from galvanizer's
waste or flux skimmings, by means of ammonia and proposed to remove the chlorine
contained in the same by means of lime previous to dissolving them in caustic
ammonia. I now find that it is more advantageous not to remove the chlorine
first, but to dissolve the skimmings in caustic ammonia by means of sulphide of
barium or strontium and then remove the chlorine from the filtrate in the shape
of chloride of barium or of strontium, by boiling down the filtrate, cooling the
liquid, and crystallizing out the hydrate of baryta or of strontia, leaving the
aforesaid chlorides in the mother liquors to be dealt with by known means to
obtain the same in a saleable form.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed.
by the said Carl Friedrich Claus in the Great Seal Patent Office on the
28th February 1883.
CARL FRIEDRICH CLAUS, of Mark Lane, in the City of London, Chemist,
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE PIGMENTS, ALKALIES, AND
ALKALINE SUBSTANCES
"
The first part of my Invention consists in a new process for the production of a
white pigment and is carried into practice as follows that is to say ;-I dissolve
finely ground uncalcined calamine or carbonate of zinc in caustic ammonia, and
after having separated by filtration the clear solution from the insoluble residuum,
I precipitate the zinc from the ammoniacal solution by means of a solution of
sulphide of an alkali or sulphide of an alkaline earth. I wish it understood that
in the term sulphides" I include the bisulphides or hydrosulphides.
"
When a sulphide of calcium, of barium, or of strontium has been used as a
precipitant, I obtain a mixed precipitate consisting of sulphide of zinc and
carbonate of lime, of baryta, or of strontia. The ammonia which has been used as
the solvent for the zinc remains in solution. This ammonia which I recover and
use repeatedly, I separate from the precipitate by filtration or distillation, or by
both these operations. I dry the precipitate and then heat the same, out of contact
with air, to a red heat, in retorts or muffle furnaces. After heating this substance
I withdraw the same from the retorts or muffles and cool it either out of contact
with air or by plunging it into water. When cool I grind and levigate it to form
the aforesaid pigment.
Q
When sulphide of ammonium has been used as the precipitant for the zinc, the
precipitate consists of sulphide of zinc only, while carbonate of ammonia and
caustic ammonia remain in solution. I separate the carbonate of ammonia and the
caustic ammonia from the sulphide of zinc precipitate by distillation. I treat
the precipitate of sulphide of zinc as above described with reference to the mixed
precipitate.
When sulphide of potassium or of sodium has been used for precipitating the
zinc from the ammoniacal solution, the precipitate consists of sulphide of zinc and
the solution will contain carbonate of potassa or carbonate of soda in addition to
the caustic ammonia which has acted as the solvent for the zinc. I separate the
ammonia by distillation and I separate the carbonate of potassa or of soda from the
precipitate, by filtration. I boil down the filtrate to form commercial carbonate of
potassa or of soda and I treat the sulphide of zinc as above described.
I produce the precipitant (that is to say the sulphide of potassium or of sodium)
for the above purpose by decomposing the sulphate of potash or of soda with
sulphide of barium or of strontium, and I produce sulphide of ammonium by
decomposing carbonate of ammonia by sulphide of barium or of strontium. A
useful product for various purposes may be produced by taking the sulphates of
baryta, or of strontia formed, and mixing them in suitable proportions with the
precipitate of sulphide of zinc. Or I add the sulphate of potassa or of soda in
solution to the solution of zinc in ammonia, and precipitate the mixture by the aid
of sulphide of barium when a mixed precipitate of sulphide of zinc and sulphate of
baryta is formed, and carbonate of potassa or soda remains in solution. The
solution is boiled down to form commercial carbonates of potash or soda.
According to another part of my invention I dissolve oxide of zinc either in
solutions of carbonate of ammonia, or in mixtures of carbonate of ammonia and
caustic ammonia and precipitate the zine from this solution by means of a solution
of sulphide of potassium, of sodium, or of ammonium, or by means of solutions of
the sulphide of barium or of strontium.

page_text: When carbonate of ammonia has been used as a solvent for the zinc and a
sulphide of an alkali has been employed as the precipitant I obtain a precipitate
of sulphide of zine, and the carbonate of such alkali and the caustic ammonia
remain in solution; but when sulphide of barium or sulphide of strontium has
been used as a precipitant, the precipitate consists of sulphide of zinc mixed with
carbonate of baryta or of strontia both of which are insoluble, there being in this
case only caustic ammonia in the solution. When mixtures of carbonate of
ammonia and caustic ammonia have been used as solvents for zinc, and sulphide of
barium or of strontium has been used as the precipitant I obtain, in addition to the
carbonate of baryta or of strontia also a quantity of hydrate of baryta or of
strontia, which is to be found in solution with the caustic ammonia. After the
ammonia has been driven off from the same by heat I obtain this hydrate of
baryta or of strontia from the said solution, by crystallization of strontia or of
baryta,
Another part of my Invention consists in a modification of a process described in
the Specification of. Letters Patent granted to me and dated the 16th day of
August A.D. 1878 No 3246 relating to the manufacture of sulphide of zinc. In
the said Specification it is stated that I dissolve the zinc from galvanizers' waste or
flux skimmings, by means of ammonia, and remove the chlorine contained in the
said waste or skimmings by means of lime, previous to dissolving the same in
caustic ammonia. I now find it more advantageous not to remove the chlorine
first, but to dissolve the skimmings in caustic ammonia, to precipitate the sulphide
of zinc by means of sulphide of barium or of strontium, and then to remove the
chlorine from the filtrate in the condition of chloride of barium or of strontium, by
boiling down the filtrate, cooling the liquid, and crystallizing out the hydrate of
baryta or of strontia, leaving the aforesaid chlorine in the mother liquor to be
dealt with by any known or suitable means, to obtain the same in a saleable form.
But if the chlorine has been removed by means of lime I dissolve the residual
oxide of zinc in a solution of carbonate of ammonia or a mixture of the same with
caustic ammonia.
Having thus fully described my said Invention and the manner of performing
the same, I wish it understood that I claim
First The process or method of manufacturing white pigment by dissolving
carbonate of zinc in caustic ammonia liquor, and precipitating with a solution of
sulphide of an alkali, or of an alkaline earth, substantially as described.
Second-The process or method of manufacturing white pigment by dissolving
oxide of zinc in carbonate of ammonia or in a mixture of this carbonate and caustic
ammonia and precipitating with a solution of sulphide of an alkali, or of an alkaline
earth, substantially as set forth.
Third The manufacture of the carbonates of alkalies from their sulphides by
either of the processes above described.
Fourth-The modification of the process or method (described in my said former
Specification) wherein I dissolve flux skimmings in ammonia without previously
removing the chloride contained in the same, for the purposes set forth.
In witness whereof I the said Carl Friedrich Claus have hereunto set my
hand and seal this Twenty seventh day of February in the year of our
Lord one thousand eight hundred and eighty three.