A NEW OR IMPROVED PROCESS FOR THE PRODUCTION OF PHOSPHATE OF SODA OR OF POTASH FROM BASIC PROCESS SLAGS AND OTHER " * PHOSPHATIO MATERIALS
Year: 1885

page_text: COMPLETE SPECIFICATION,
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst. P.A. of the Agency for Foreign Patent
Solicitors, 6 Lord Street, Liverpool in the County of Lancaster, and 323 High
Holborn, in the County of Middlesex, Civil Engineer, do hereby declare the nature
of the said invention for A NEW OR IMPROVED PROCESS FOR THE PRODUCTION
OF PHOSPHATE OF SODA OR OF POTASH FROM BASIC PROCESS SLAGS AND OTHER
"
*
PHOSPHATIO MATERIALS (a communication from abroad by Luigi Imperatori
of Düsseldorf in the Empire of Germany, Engineer) and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
The process which forms the subject of the present application for Letters
Patent has for its object the conversion of the phosphoric acid contained in
Thomas Gilchrist process slags and other materials containing phosphates of lime
into a combination soluble in water as hereinafter described. The slag suitably.
crushed and pulverised is mixed with carbon and sulphate of soda. The same
proportion of carbon to sulphate of soda is employed as in the Leblanc process say
about 40 parts C per 100 Na. SO'
With a weathered basic process slag containing say per 100 parts, 50 parts Lime,
5 parts Magnesia, 19 parts Iron, 20 parts phosphoric acid, 6 parts Silicic acid;
the following reactions are obtainable on smelting it with carbon and sulphate
of soda.
a. The lime uncombined with phosphoric or silicic acid yields with sulphate of
soda Na, CO, or if the slag has not been weathered, Na. O as in the Leblanc
process.
}
b. The iron in the shape of Fe O and Fe³ Os also yields with carbon and
sulphate of soda Na, O and sulphide of iron.
c. The phosphate of lime, sulphate of soda and carbon yield finally sulphide of
calcium and basic phosphate of soda. The process carries out the reaction
expressed by the equation Ca³ (PO)² + 3 Na₂ SO' + 6 C = 3 Ca S2 Na³
PO' + 6 CO₂.
The silicic acid of the slag is obtained also in the fluxed mass combined with
lime.

page_text: The following equations serve to indicate the proportions of soda salt to
phosphate required.
56 (Ca O)
-
50 Co of the cloned
100
Theoretically therefore, the proportions are; slag 100 parts, sulphate of soda
176 parts, coal 74 parts. In practice however, a considerable excess of slag is
advisable.
The mixture is then put into a black-ash furnace, and fluxed and worked as
usual in the Leblanc process whereby a semi fluid mass is obtained which is
moulded into blocks. These blocks are not broken up and lixiviated on cooling as
in the ordinary soda process, but subjected to special treatment as follows:
At the high temperature at which the reactions take place there occurs also
partial decomposition of Na, CO, and Ca S with loss of carbonic acid, according to
the equation Na, CO³ + Ca S = Na, S + Ca O + CO₂.
Moreover the excess of slag used produces a certain quantity of free lime. This
free lime causes the soluble phosphate to revert almost entirely if the fluxed mass
be lixiviated directly with water. To avoid this, the mass is previously treated
with carbonic acid so as to convert the caustic lime into carbonate. The carbonic
acid may be supplied in various ways for instance.
a. In the form of gas. The blocks are crushed to the size of nuts, put into a
scrubber and gas passed through-or
b. The broken up mass is mixed with bi-carbonate of soda, the mixture ground,
warmed to 100 degrees Centigrade and lixiviated, or,
c. The broken up mass is treated with a saturated solution of soda, through
which carbonic acid has been passed until it is no longer clear, and subsequently
ground to the consistency of mortar, through which carbonic acid is passed.
During the carbonic acid treatment a portion of the sulphide of calcium is also
decomposed into sulphuretted hydrogen and carbonate of lime, and the basic
phosphate of soda Na³ PO* converted into neutral phosphate of soda Na² H PO
After this operation the mass is lixiviated together with the neutral phosphate
of soda, large quantities of carbonate of soda are dissolved out. Both salts may
be obtained and separated by crystallization. The larger the percentage of free
lime in the material, the greater the quantity of carbonate of soda in the product.
The process is obviously applicable to other sources of phosphoric acid besides
the Thomas Gilchrist process slags. Instead of sulphate of soda, sulphate of potash
may be made use of.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is
The process for obtaining phosphate of potash or soda from Thomas Gilchrist
process slags or other phosphatic materials by smelting the same with sulphate of
potash or soda and carbon, and treating the product with carbonic acid substantially
as described.
Dated this 9th dow of Ausil tooe