Improvements relating to the Manufacture of Acid Phosphates for use as Artificial Manure.
Year: 1890

page_text: Date of Application, 12th June, 1890-Accepted, 19th July, 1890
[Communicated from abroad by ALLARD MEMMINGER, of 6, Broad Street, Charleston,
South Carolina, United States of America, Doctor of Medicine.].
Improvements relating to the Manufacture of Acid Phosphates for
use as Artificial Manure.
I, HENRY HARRIS LAKE of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings in the County of Middlesex, do hereby declare the nature of
this invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
The invention relates to the manufacture of acid phosphates from phosphatic rock,
the said phosphate being, as is well known, used as artificial manures.
The invention consists more particularly in the addition of a fluoride compound
to the ground or comminuted phosphatic material mixed with acid, whereby
among other advantages hereinafter detailed, the time of drying of the resulting
product is greatly diminished.
The manufacture of acid or super-phosphates is commonly based upon the treat-
ment of the pulverized or ground rock with sulphuric acid. In order to ensure
a thorough reaction, it is customary to grind the rock very finely, and usually so
that the powder will pass through a sieve having 80 meshes to the inch. The
powder is then stirred with a large percentage of sulphuric acid ordinarily of a
density of about 50 degrees Beaumé, after which the mixture is dried by exposure
to the air. The phosphate from "land" rock such as is found in South Carolina,
United States of America, requires under these conditions from five to six days to
become sufficiently dry to allow of its being packed and shipped.
The period of drying, however, will depend greatly first upon the fineness of
pulverization, second, upon the strength of the acid employed, and third, upon the
constituent character of the rock. Thus the "land" phosphate above named, com-
minuted
d_to pass through a forty mosh sieve, will take about two weeks to dry.
Lowering the density of the acid also retards the drying operation. Finally there
are varieties of phosphate rock (especially prevalent in Florida, U.S. of America),
which, with the necessarily large combining proportion of acid used, produce a pasty
mass which it is nearly impossible to dry, and which is therefore incapable of being
handled and unmarketable. On the other hand, it is well known that there are kinds
of phosphate rock, which dry much more readily than other varieties and hence it
is not uncommon to mix a proportion of quick drying rock or even of common marl
with the slow drying phosphate material, and in this way to accelerate to some extent
the dessication of the whole.
:
By the simple addition of a fluoride to the mixture of phosphate rock and acid,
the drying operation can be greatly hastened. The addition of the fluoride renders
such fine grinding of the rock as is common, unnecessary, and excellent results are
obtainable when the comminution is not beyond that of the condition of a powder
which will pass through a 40 mesh sieve. As a further advantage of this process,
sulphuric acid of at least 5 degrees lower density may be employed successfully.
The process is carried into effect as follows: Supposing the phosphate rock
employed to be South Carolina land rock, or rock of similar character. To a given
amount of said rock, five per cent. of calcium fluoride (fluor-spar) is added, grinding
the two materials together to pass through a 40 mesh sieve. The combined substances
are then mixed with about 45 per cent. of sulphuric acid at say 50 degrees Beaumé,
and after being stirred are turned out. The mass will be found to dry in about
48 hours. If, however, the rock be pulverized to pass through an 80 mesh sieve, the
drying will occur in about half of the above period.
It will be apparent, therefore, that the proportion of fluoride to be added will

page_text: depend largely upon the degree of comminution of the rock. The more fine the
pulverization, the less the proportion of fluoride; and the coarser the pulverization,
the more fluoride required. Of course it is to be understood that such a proportion
of fluoride must not be added as to produce too rapid drying, as this might interfere
with the proper action of the acid. It will thus be apparent that not only is quick
drying of the fertilizer ensured, but the period of drying can be regulated so as to
suit any given character of rock under treatment, by simply varying the proportion
of fluoride employed, or by keeping the proportion of fluoride constant and varying
the degree of pulverization of the rock. In dealing with a normally quick drying
rock, a less proportion of fluoride is used; it, on the contrary, phosphate rock,
which requires so much acid that the mixture practically refuses to dry, is treated,
a greater proportion of fluoride is used.
The invention is not limited to the use of calcium fluoride, because other fluoride
compounds, such as sodium or potassium-fluorides, might be employed. Calcium
fluoride is preferred on account of its abundance and cheapness. So also the treat-
ment of the phosphate rock by sulphuric acid in contradistinction to other acids, such
as nitric or hydro-chloric, is not essential to my process.
Among other advantages secured by this process are, that the acid in the manu-
factured fertilizer is produced in a practically anhydrous condition.
It does not,
therefore, attack the bags in which the manure is packed, as is the case when the
acid by reason of an excess of water, is produced in the hydrated form. The losses
so due to this destruction of bags by super-phosphates produced in the ordinary
way are large, and up to this time, no efficient means has been devised for preventing
them.
The possibility of quick and of graduated periods of drying opens to commerce an
immense area of phosphate deposits, throughout the world, which, for the reasons
already given, have hitherto been regarded as unworkable.
Finally, the quick drying results in the production of the phosphate in a friable
and easily disintegrated condition, and hence in a state more suitable for fer-
tilizing purposes, and allows of more rapid shipment of the material than has hitherto
been possible.
Having now particularly described and ascertained the nature of my said inven-
tion 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:
1. The use of a fluoride compound in the manufacture of acid phosphates from
phosphate rock.
2. The mode of accelerating the drying period or of enabling the duration of the
same to be graduated, of a mixture of comminuted phosphate rock and acid, by adding
thereto a fluoride compound, such as calcium fluoride.
Dated this 12th day of June 1890.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.