IMPROVEMENTS IN THE TREATMENT OF PHOSPHATES OF IRON AND ALUMINA, AND OBTAINING USEFUL PRODUCTS THEREFROM
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Henry Young Darracott Scott at
the Office of the Commissioners of Patents, with his Petition, on
the 17th September 1875.
I, HENRY YOUNG DARRACOTT SCOTT, of Ealing, in the County of
Middlesex, Major General, C.B., do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE TREATMENT OF PHOSPHATES OF IRON AND
ALUMINA, AND OBTAINING USEFUL PRODUCTS THEREFROM," to be as follows:
-
The object of this Invention is chiefly the extraction of phosphoric
acid from natural phosphates of alumina and iron (such as the redonda
and El Roque phosphates) in a marketable form without any preliminary
treatment; except grinding, or in some cases roasting, but it is also
applicable to phosphates of alumina or iron which have been digested in
acid and purposely precipitated, or which have resulted from sewage
precipitation.
I carry out my Invention in its simplest forms as follows:-I add
sulphide of calcium to gas liquor, decomposed urine, or other ammoniacal
liquid of like nature, and I subject this mixture to heat when the
following changes take place. The lime of the sulphide of calcium

page_text: unites with the carbonic acid of the carbonate of ammonia to form
carbonate of lime, and the sulphur of the sulphide of calcium unites
with the ammonium to form the volatile compound sulphide of
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ammonium which is the agent I require for my process.
I may also obtain my sulphide of ammonium-by-other-modes. well.
known to chemists.
In gas liquor a variable proportion of sulphide of ammonium is found,
unless purposely removed, and to the extent to which it exists the
sulphide of calcium employed may be reduced in quantity.
In urine the quantity of sulphide of ammonium is too insignificant
to be considered. A distillation of the above mixture is then carried
out in a distilling apparatus of ordinary kind, and the distillate is
received in a condensing vessel or vessels provided with agitating
apparatus, wherein is suspended (in a sufficient quantity of water to
detain the sulphide of ammonium in a state of fine division or as a
precipitate) the phosphate to be operated upon.
If the substance to be treated is purely phosphate of iron, the result
will be that the iron will unite with the sulphur of the sulphide of
ammonium to form the insoluble mono-sulphide of iron, and the
phosphoric acid will unite with the ammonia, forming phosphate of
ammonia, which remains in solution, as is well known to chemists, but
in proportion as phosphate of alumina predominates in the compound
operated upon (and phosphate of alumina is found in greater or less
quantity in all the natural phosphates imported, forming. in the case of
-the-redonda phosphate by far the largest constituent of the mineral)
the proportion of sulphide of calcium employed to decompose the
ammoniacal-liquid is to be reduced and lime-substituted, for inasmuch
-as the alumina does not combine with the-sulphur-(as-iron does), but.
is simply thrown out as alumina (whilst the sulphur is evolved as
sulphuretted hydrogen) free ammonia is alone wanted to complete a
chain of decomposition and recomposition which will effect all that is
required-in operating upon phosphate of alumina. The same equivalent
of sulphur in fact enables equivalent after equivalent of phosplioric acid
to be set free by the continuous addition of ammonia.
Ammonia results as is well known from the treatment of ammoniacal
liquids with lime, the lime combining with the carbonic acid of the

page_text: ·
carbonate of ammonia, whilst the base is set free. The removal of the
carbonic acid from the ammonia is necessary, because carbonic acid
expels sulphuretted hydrogen from an ammoniacal solution; and I may
here add that it is not sufficient to remove the carbonic acid from gas
liquor and decomposed urine, and then saturate the solution of ammonia
thus obtained with sulphur, as a mode of preparing the material with
which to operate upon the phosphate, unless such phosphate be
phosphate of iron, for the chloride of ammonium present in the
undistilled liquid leaves phosphate of alumina in an insoluble form.
The phosphate of ammonia resulting from the above described process
may (after separation from the insoluble residue left by the operation)
be treated in a variety of ways so as to be brought into useful and
marketable forms. These are too well known to manufacturing chemists
for it to be necessary to specify them.
The sulphur of the insoluble sulphide of iron which rapidly oxydates
on exposure to the air, can be recovered by well known methods, and
the oxide of iron can be used for purifying coal gas, or both the oxide of
iron and alumina can be used in the preparation of salts of these
substances.
The substitution of soda waste for sulphide of calcium specially
prepared and for lime is obvious.