Improvements in the Treatment of Hydrated Phosphates of Alumina and Iron for Obtaining an Improved Fertilizer.
Year: 1893

page_text: Date of Application, 21st Mar., 1893-Accepted, 6th May, 1893
COMPLETE SPECIFICATION.
[Communicated from abroad by ALFRED MONTGOMERY GOODALE, of Waltham,
MARCIA WINTER
State of Massachusetts, Cotton Manufacturer, and
ANDERSON SPRING, of Portland, State of Maine, Married Woman, both in
the United States of America.]
Improvements in the Treatment of Hydrated Phosphates of Alumina
and Iron for Obtaining an Improved Fertilizer.
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 :--
My invention relates to the manufacture of a plant food or concentrated fertilizer,
from insoluble hydrated phosphates of alumina and of iron, whose large contents of
phosphoric acid, essential to plant growth become accessible to plants in nature only
as slowly disintegrated by "weathering."
I have found that heat alone can be so applied as to produce such a change in
these phosphates
as to render them readily citrate soluble, commonly called
"available and assimmilable by plants; and that to attain this result, the heat
must be sufficient to expel the combined water, and must not be so great as to,
disturb the organization or constitution thus brought about. The product is a
different fertilizer from that previously produced being free from dilution or
adulteration by chemicals as in other processes, and is a better fertilizer as it
furnishes more available phosphoric acid, and is a cheaper fertilizer to manufacture
and to transport.
66
It has been the common method to simply grind these phosphates and mix with
'slag" or other substances for use as a slow fertilizer; but my process renders
very much more (substantially all) of the phosphoric acid presently absorbable by
the plant-roots a commercial test of the degree of said assimilability and solubility
by plants being well known and found in a solution of basic aminonium citrate. So
much of the manufactured phosphate as can dissolve in a solution of basic
ammonium citrate of customary strength by sufficient digestion, is also soluble or
"available "although not all
assimilable by plants and is properly described as
soluble in water alone.
My invention consists in a process or method of rendering these phosphates
available as fertilizers.
The scope and practice of my invention will be more readily understood by
reference to the state of the art of manufacturing such plant food. It is well known
that plants absorb phosphoric acid from the soil and grow thereby, and the value
of fertilizer from these phosphates depends upon their large amount of phosphoric
acid being rendered readily assimilable by plants.
Hitherto these crude phosphates have been rendered fit for plant food as a rapid
fertilizer only by aid of some second substance. The sulphuric acid process for
manufacturing fertilizer from phosphates of lime cannot be used with these
phosphates. But treatment with other chemicals (muriatic acid, caustic lime, soda
and potash, sulphates and other re-agents) or mechanically mixing with less active
substances, have been practised. Practically however, all these processes have been
but partially successful, involving dilution, or excessive cost, and only occasionally
and accidentally rendering the maximum of phosphoric acid available.
Under my invention, I not only render more phosphoric acid available and more
speedily so, but I do it without the expense or the aid of any second material, and
I obtain a different, a cheaper, and a better plant food.
i

page_text: I have been led by a long course of experiments to my discovery which is two-
fold; first, that plants can readily and rapidly assimilate or convert the phosphoric
acid of these phosphates from their residium alone just as it is left after elimination
by heat of the water of constitution; and secondly, that such residium can be
obtained by properly applying only such definite amount of heat as not to develope
unfavorable molecular re-arrangement, or, if this cannot be considered a
demonstrable statement, as not to impair this condition of solubility; inasmuch as
heat in proportion as it goes beyond the requisite amount, is sooner or later
destructive of the desired solubility and assimilability of the residue.
My process of manufacturing this plant food or fertilizer based upon the fore-
going discoveries will be seen to be not only simple and certain, but distinct from
prior processes whether successful or unsuccessful. None of the steps, in and of
themselves which I take with the crude material, are novel, although they are
entirely so as to the rules by which they are taken, and as applied to this subject-
matter, and for this purpose. For instance, it has long been known that in
determining chemical constituents by analysis; hydrous or other volatile elements
may be eliminated by means of heat, as is sometimes expressed by the word
calcining." But my process consists essentially in so applying heat and limiting
its degree that while the combined water shall be entirely expelled no injury shall
be done to the residue by excess of heat, whereby its solubility is impaired.
"
My manufacturing process then is comparatively simple. There must be a
suitable heating receptacle for the raw material, having a vapor outlet. It must
be so constructed that the heat will be admitted and distributed uniformly.
Ordinary methods of controlling the heat will be found necessary. Heat should
not be applied directly, as by an incandescent material or flame coming in contact
with the phosphate. The heat must be applied within limits, which, although
somewhat variable, are quite determinable. This variability arises mainly from
three sources, first, differing proportions of iron or alumina in different samples of
the phosphates; second, varying degrees of hydration ranging from 16 per cent.,
(or occasionally below) to 25 per cent. (or occasionally above); and third, the
presence of accidental or indifferent matters containing no combined water. Tests
in a small way may determine this for given lots.
In most cases the proper affect of the heat will be secured at about 325° centi-
grade. I more exactly determine the necessary amount of heat in any given case
by exposing from time to time, as the heat approaches 275° centigrade, a metallic
or other proper cold surface to the orifice where escaping invisible vapor, can be
recognised by being deposited on the cold surface as dew and when this deposit
ceases further increase of heat must be arrested lest the condition of solubility be
destroyed.
So far as this is a variable rule, it is at the same time definite, inasmuch as
although it describes no absolute fixed temperature, it yet contemplates variation
in the rule only as the crude samples vary. Heat to the requisite amount having
been thus applied its further increase is arrested.
If large quantities are to be treated at one operation great care should be given
in regard to continuance and especially to increase of heat near the end, in order
to avoid over-passing the proper limit. This is especially needful for an operator
before he has acquired sufficient practical familiarity with the manipulation
appropriate to phosphates, and which should allow for the continuance of heat
after the drafts have been closed. These rules will be found complete, satisfactory
and successful; although there may be variations in the raw material other than
what I have noticed. In my experience the water of constitution in different
samples varies as I have intimated; about 275° centigrade has appeared to be the
maximum of heat for the least hydrated samples and from that to 350° centigrade
for samples having the maximum water of constitution.
Having thus explained my discoveries and described the way in which they are
to be applied in the new process by means of heat alone by which means for the
first time not only has a fertilizer or plant food but a different and better one been

page_text: obtained from these phosphates, I do not wish to be understood as claiming broadly
the chemical procedure which chemists have for many years termed dehydration,
nor of course the process of calcining without reference to specific subject matter
and under specific rules.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents I declare that what I claim is :-
First. The art or process of rendering insoluble hydrated phosphates of alumina
and of iron easily soluble and so available as rapidly acting plant fertilizers, which
consists in heating these phosphates, in suitable receptacles, by the indirect
application of heat, until all the water of constitution is expelled, or usually, until
heat has been applied sufficient to raise the temperature of the mass to about
325° C. and then arresting the heat and allowing the resulting product to cool
spontaneously, substantially as and for the purpose described.
Second. The improved product, fertilizer and plant food, consisting of the
residium of hydrated phosphates of alumina, or of iron or of both alumina and
iron from heating and not burning said crude phosphates until all their water of
constitution is expelled, or usually until the temperature of the mass reaches about
325° centigrade; substantially as described.
Dated this 21st day of March 1893
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.