IM- PROVEMENTS IN THE MANUFACTURE OF MANURES AND PHOSPHATES
Year: 1878

page_text: LETTERS PATENT to Sidney Gilchrist Thomas, of 3, Queen's Road Villas,
Queen's Road, Battersea, in the County of Surrey, for the Invention of "IM-
PROVEMENTS IN THE MANUFACTURE OF MANURES AND PHOSPHATES."
Sealed the 2nd May 1879, and dated the 9th November 1878.
PROVISIONAL SPECIFICATION left by the said Sidney Gilchrist Thomas
at the Office of the Commissioners of Patents on the 9th November 1878.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Battersea,
in the County. of Surrey. IMPROVEMENTS IN THE MANUFACTURE OF MANURES
AND PHOSPHATES."
+5
My Invention consists in treating the calcareous phosphoretic slags produced in
treating phosphoretic pig iron in furnaces lined with basic calcareous materials, so
that the large amount of phosphoric acid contained in the slags may be utilised for
manure or the manufacture of phosphates or phosphorus. By my present Inven-
tion I effect this utilisation without any preliminary calcination of the slag. The
slag while still hot from the furnace or converter is thrown into water, by which it
is disintegrated. It is then crushed fine by rollers or stamps, and treated in vats
or revolving cylinders with cold acid. The acid I prefer to use is a very dilute
sulphuric acid containing not more real acid than will suffice to combine with the
lime in the slag, the object being to dissolve out as little iron as possible. The
solution after being cleared by standing is drawn off and evaporated. During the
evaporation, part of the dissolved iron is crystallised out as copperas. If it is desired
to free the phosphate entirely from iron the residue after complete evaporation is
calcined with access of air and the phosphate taken up by acidulated water.
phosphates may also be precipitated by ammoniacal gas liquor or sewage, by
which the sulphate of iron will be decomposed and sulphate of ammonia formed,
which may be recovered in the usual way from the solution.
The

page_text: Instead of treating the ground slag with sulphuric acid, as is generally preferable,
a cold solution of sulphurous acid may be used, and the phosphate precipitated
either by treating the solution and recovering a great part of the sulphurous acid
or by treating the solution with ammonia liquors. Cold acetic or cold dilute
hydrochloric acid may also be used to dissolve out the phosphates. Acetic acid
can only be used where the crude acid is very readily obtainable, and purified
acetic acid is recovered by treating the solution of acetate and phosphate of
lime, &ct., with strong sulphuric acid. The hydrochloric acid solution may after
evaporation be treated with sulphuric acid so as to obtain the phosphates in the
ordinary form of superphosphate.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by.
the said Sidney Gilchrist Thomas in the Great Seal Patent Office on the 9th
May 1879.
SIDNEY GILCHRIST THOMAS, of 3, Queen's Road Villas, Queen's Road, Battersea,
in the County of Surrey. "IMPROVEMENTS IN THE MANUFACTURE OF MANURES
AND PHOSPHATES.'
"
My Invention consists in treating the calcareous phosphoretic slags produced in
treating phosphoretic pig-iron in Bessemer converters and open-hearth furnaces
lined with basic materials, so that the large amount of phosphoric acid contained
in the slags may be utilised for manure or for the manufacture of phosphates. By
my present Invention I effect this utilisation without any preliminary calcination
of the slag. I prefer that the slag while still hot from the furnace or converter
should be thrown into water, and so considerably disintegrated. It is then crushed
fine between rollers or stamps, and treated in vats or revolving cylinders with cold
acid preferably for several days. The acid I prefer to use is a very dilute sulphuric
acid containing not more real acid than will suffice to combine with the lime
present in the slag, and not having a greater strength than about 20 (twenty) per
cent. of real acid, so as to dissolve as little iron as possible. The solution after
being cleared by standing is drawn off and evaporated. In the course of the
evaporation a considerable part of the dissolved sulphate of iron is crystallised out;
the phosphate may be obtained quite free from iron by igniting the residue after
evaporation and taking up the phosphate with very weak acid.
The phosphate may also be precipitated by lime or chalk, and will be nearly free
from iron; or it may be precipitated by ammoniacal gas liquor, by which the
sulphate of iron will be decomposed and sulphate of ammonia formed, which may
be recovered from the solution by evaporation in admixture with part of the
phosphate. Instead of treating the ground slag with sulphuric acid a cold solution
of sulphurous acid may be used, from which the phosphate is precipitated by
heating the solution, and a great part of the sulphurous acid is recovered.
In localities where hydrochloric acid is cheap, treatment with hydrochloric acid
is the most economical, a diluted tower-acid being used in about the proportion
of 40 to 50 parts (forty to fifty parts) of real acid to 100 parts (one hundred parts)
of the ordinary calcareous converter or open-hearth slag.
The exact amount of acid required to extract the whole of the phosphate from a
particular slag is best determined in each case by experiments. The acid is diluted
so as to contain not more than about 20 (twenty) per cent. of actual acid.
I precipitate the solution with chalk or lime."
I claim the treatment of highly calcareous phosphatic Bessemer or open-hearth
slags with cold dilute sulphuric or hydrochloric acid or with sulphurous acid, and its
subsequent treatment as described, so as to extract the phosphate of lime in a
marketable form.
In witness whereof, I, the said Sidney Gilchrist Thomas, have hereunto set
my hand and seal, this Ninth day of May, in the year of our Lord Eighteen
hundred and seventy-nine.
SIDNEY GILCHRIST THOMAS. (L.S.)