IMPROVEMENTS IN THE MANUFACTURE OF SILICATE OF ZINC, OF LEAD, OF BARYTA, AND OF STRONTIA."
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 MANUFACTURE
OF SILICATE OF ZINC, OF LEAD, OF BARYTA, AND OF STRONTIA."
PROVISIONAL SPECIFICATION left by the said Carl Friedrich Claus at the
Office of the Commissioners of Patents on the 29th August 1882.
CARL FRIEDRICH CLAUS, of Mark Lane, in the City of London, Chemist,
"IMPROVEMENTS IN THE MANUFACTURE OF SILICATE OF ZINC, OF LEAD, OF
BARYTA, AND OF STRONTIA
33
My Invention relates to the manufacture of various silicates as herein specified.
I obtain silicate of zinc by dissolving oxide of zinc in caustic ammonia, or in a
solution of carbonate of ammonia, or mixtures of both, and precipitate the same
from such solution by means of solutions of silicate of potash or silicate of soda.
The precipitate of silicate of zinc is filtered off from the liquid. The filtrate
consists of a solution of caustic potassa or caustic soda and caustic ammonia; or, if
carbonate of ammonia has been used as a solvent for the oxide of zinc, the filtrate
consists of carbonate of potash or carbonate of soda. I separate the ammonia from
the caustic potash or soda or from the carbonate of potash or of soda by distillation.
The solution of caustic potash or caustic soda I may use repeatedly for the
manufacture of silicate of potash, or of soda, in the manner known to chemists, that
is to say, by boiling flints in these caustic alkalies, under pressure. If a solution of
carbonate of these alkalies is a constituent of the filtrate, I boil the same down to
dryness and use the desiccated carbonates for the manufacture of the silicates of
these alkalies in the manner now practised.
If the oxide of zinc is dissolved in caustic potash or caustic soda, I precipitate
the silicate of zinc also by means of solutions of silicate of potash or of soda, filter
off the precipitate from the solution of caustic potash or of caustic soda, and utilize
these alkalies repeatedly in the manner above specified.
To produce the silicate of lead I proceed in an analogous manner to that above
described in reference to zinc, but as oxide of lead is insoluble in ammonia I use

page_text: caustic potash or caustic soda as the solvent for the oxide of lead, that is to say,
I precipitate the lead by means of the above named alkaline silicates; filter, and
dry the precipitate, and utilize the caustic alkalies in the manner above stated.
I obtain the silicates of baryta and of strontia by precipitating them from
solutions of sulphide of barium or sulphide of strontium, by means of solutions of
silicate of potash or of silicate of soda, I filter the precipitate of silicate of baryta
or of silicate of strontia and wash the same, and the filtrate which, in this case,
consists of solutions of sulphide of potassium or of sulphide of sodium, I boil down,
preferably in closed vessels, until it is sufficiently concentrated to be completely
desiccated. I then desiccate the same and when nearly dry I mix it with sand
and some carbonaceous substance and manufacture silicate of potash or silicate of
soda respectively from the same by fusion at high heat in the reverberatory
furnace.
The silicates of zinc, of lead, of baryta and of strontia may be used for the
manufacture of glass, or may be used as glazing material for pottery. To give them
more density, than the precipitates naturally have after filtration and drying, I heat
the same in a reverberatory furnace until they have attained the density desired.

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 SILICATE OF ZINC, OF LEAD, Of
BARYTA, AND OF STRONTIA
"
My Invention relates to the manufacture of various silicates as herein specified.
I obtain silicate of zinc in the following manner, that is to say, I take a solution
of oxide of zinc in caustic ammonia, or a solution of this oxide in carbonate of
ammonia, or in mixtures of both (or I take a solution of carbonate of zinc in
caustic ammonia) and I precipitate the silicate of zinc therefrom by means of a
solution of silicate of potash or silicate of soda. The precipitate of silicate of zinc
is filtered off from the liquid. When caustic ammonia has been used as the
solvent, the. filtrate consists of a solution of caustic potash (or caustic soda) and
caustic ammonia; if carbonate of ammonia has been used as a solvent for the oxide
of zinc, or if carbonate of zinc has been dissolved in caustic ammonia the filtrate
consists of carbonate of potash or carbonate of soda. I separate the ammonia from
the caustic potash or soda, or from the carbonate of potash or of soda, by distillation
The solution of caustic potash or caustic soda I use repeatedly for the manufacture
of silicate of potash or of soda in the manner known to chemists, that is to say, by
boiling flints in these caustic alkalies under pressure. If a solution of carbonate of
either of these alkalies is a constituent of the filtrate I boil the same down to
dryness and use the desiccated carbonate for the manufacture of the silicate of
such alkali in the manner now practised.
Instead of the above named solutions I sometimes take a solution of oxide of
zinc in caustic potash or caustic soda, and I precipitate the silicate of zinc there-
from by means of a solution of silicate of potash or of soda and utilize these
alkalies repeatedly in the manner above specified.
To obtain silicate of lead from solutions of oxide of lead I proceed in an
analogous manner to that above described with reference to zinc, but as oxide of
lead is insoluble in ammonia I use in all cases caustic potash or caustic soda as the
solvent therefor; that is to say I precipitate the lead by means of the above named
alkaline silicates, filter and dry the precipitate, and utilize the caustic alkalies in
the manner above stated
I obtain the silicate of baryta or of strontia by precipitating the same from a
solution of sulphide of barium or sulphide of strontium by means of a solution of
silicate of potash or of silicate of soda; I filter the precipitate of silicate of baryta
or of silicate of strontia and wash the same The filtrate, which consists of a
solution of sulphide of potassium or of sulphide of sodium, I use either in that form
for any desired purposes or I boil it down (preferably in closed vessels) until it is
sufficiently concentrated to be completely desiccated. I then desiccate it, and when
nearly dry, I mix it with sand and some carbonaceous substance and use it for the
manufacture of silicate of potash or silicate of soda by fusion at high heat in the
reverberatory furnace.
In the precipitation of the silicates of zinc, lead, baryta, or strontia from solutions
of these substances as above described by means of silicate of soda or potash, if the
silicate of soda or of potash used is present in excess some of the same will enter
into chemical combination with the metallic silicate, these silicates remaining
associated and forming an insoluble compound. The alkali or its silicate which has
in this manner become abstracted from the liquid can obviously not be recovered for
repeated use in the process; the solution therefore has to be replenished.

page_text: The double compound of silicate of zinc, of lead, of baryta, or of strontia with
silicate of soda or silicate of potash is more useful for the purposes for which such
materials are employed than any single one of these silicates.
The silicates of zinc, of lead, of baryta and of strontia may be used for the
manufacture of glass or as glazing material for pottery. To give them more
density than the precipitates naturally have after filtration and drying, I treat the
same in a reverberatory furnace until they have attained the desired density.
Having thus fully described my said invention and the manner of performing
the same, I wish it understood that I claim
First:-
-The manufacture of silicate of zinc or of lead by a process in which the
same is precipitated from an alkaline solution by means of a solution of silicate of
potash or of soda, and in which the alkaline solvent is repeatedly recovered and
used.
Second-The manufacture of silicate of baryta or of strontia by a process in
which the same is precipitated from its sulphide by means of silicate of potash or
silicate of soda, and in which the potash or soda is repeatedly recovered and used, as
above described
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.
CARL FRIEDRICH CLAUS. (L.S.)