IMPROVEMENTS IN THE MANUFACTURE OF DUPERPHOSPHATE OF LIME
Year: 1871

page_text: LETTERS PATENT to Benjamin Tanner, of New Brighton, in the
County of Cheshire, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF DUPERPHOSPHATE OF LIME.
•
PROVISIONAL SPECIFICATION left by the said Benjamin Tanner at the
Office of the Commissioners of Patents, with his Petition, on the
28th April 1871.
I, BENJAMIN TANNER, of New Brighton, in the County of Cheshire,
do hereby declare the nature of the said Invention for “IMPROVEMENTS
in the ManufacTURE OF SUPERPHOSPHATE OF LIME," to be as follows:-
This Invention consists in certain improvements in the manufacture
of superphosphate of lime for the purposes of artificial manure, and
whereby the same is produced in an economical manner and in a
highly concentrated form, whilst such control is afforded over its
solubility as to enable it to be produced in such condition that it shall

page_text: act with great rapidity when applied to the land, or to be more slowly
available for the growing crops, according as the peculiar requirements
of soil may render desirable. For the convenience of description and
reference the following paragraplis, in which the processes embraced by
this Invention are described, are numbered consecutively.
1. Solutions of phosphate of lime in hydrochloric acid are obtained by
taking any of the ordinary forms of phosphate of lime of commerce
(such as phosphorite, coprolites, apatite, phosphatic guanos, bone ash,
or animal charcoal), or any form of precipitated phosphate of lime, or
any other form of phosphate of lime or mixtures thereof which are
capable of being dissolved in hydrochloric acid, using by preference acid
varying in strength from 15° to 20° Twaddel's hydrometer, and having a
specific gravity of from 1.075 to 11. The hydrochloric acid is some-
times used at a temperature of from 80° to 140° Fahrenheit, which it is
found assists the solution of the phosphate of lime considerably. These
solutions are also obtained by passing hydrochloric acid in the gaseous
state through the above-named phosphates, subsequently flushing the
same with water. Solutions are also obtained by treating any of the
above-named varieties of phosphate of lime with strong hydrochloric acid,
using by preference acid having a strength of from 25° to 30° Twaddel's
hydrometer and having a specific gravity of 1·125 to 1·15. A crystalline
mass is thus formed, to which I add sufficient water to remove all the
soluble salts thus formed. These being removed in solution a further
quantity of strong hydrochloric acid is added to any phosphate of lime
remaining, and by the use of water the soluble salts formed are removed,
and this is repeated until the phosphate of lime is exhausted. The
carbonate of lime present in the above-named varieties of phosphate of
lime is sometimes decomposed by the use of phosphoric acid, and
the phosphate of lime then dissolved by hydrochloric acid, as already
described.
2. Solutions of any of the forms of phosphate of lime before described
or mixtures thereof are also obtained by the use of phosphoric acid and
water, whereby any carbonate of lime present is decomposed, a solution of
the phosphate of lime also obtained. The solutions are also obtained by
adding phosphoric acid and water to any of the above-named forms of
phosphate of lime or mixtures thereof, whereby a crystalline mass is
Further additions
formed which is subsequently removed by water.
of phosphoric acid and water are made until the phosphate is entirely

page_text: dissolved out and obtained in solution. The crystals thus produced are
superphosphate of lime, and are sometimes collected for use in this
form and condition, but it is preferred to dissolve the crystals in water
and treat the solution as herein-after described.
3. Having by the foregoing and similar arrangements obtained
solutions of any of the forms of phosphate of lime as already described
or mixtures thereof in hydrochloric acid or in phosphoric acid, or in
mixtures thereof, the solution is examined and its chemical composition
determined. Subject to the principle laid down in the 15th paragraph
of this Provisional Specification it is preferred to have the phosphoric
acid and lime or calcium present in the proportion of 71 parts of
phosphoric acid for 28 of lime, or 20 of calcium. If it is found that the
lime or calcium is present in excess of the required quantity, then the
solution is dealt with as described in the 4th, 5th, and 6th paragraphs
hereof. If it is found that the phosphoric acid is in excess of the
required quantity the solution is dealt with as described in the 7th
paragraph hereof. But if it appears that the phosphoric acid and lime or
calcium are present in the required proportions the solution is evaporated
in suitable vessels, continuing and increasing the heat as may be necessary,
and the dry product is superphosphate of lime. Any hydrochloric acid
vapours thrown off during the evaporation and final decomposition are
collected and condensed.
4. To the said solutions of phosphate of lime is added sufficient sul-
phuric acid to remove all the calcium or lime present, with the exception
of one combining equivalent of calcium or lime for every equivalent
of phosphoric acid present in the solution, that is to say, 20 parts of
calcium or 28 parts of lime are left in the solution for every 71 parts of
phosphoric acid. The precipitated sulphate of lime is then separated
by filtration, or the precipitate allowed to subside and the supernatant
liquor then decanted off. Having washed the sulphate of lime so
obtained with water to displace all the original liquor, the original
liquor and these washings are then evaporated in suitable vessels to
dryness, continuing and increasing the heat as may be necessary. The
dry residue thus obtained is superphosphate of lime. Any hydrochloric
acid vapours set free during evaporation and final decomposition are
collected and condensed.
5. The said solutions of phosphate of lime are also treated by the
addition thereto of sufficient oxalic acid to combine with all the calcium

page_text: or lime present, with the exception of one combining equivalent of
calcium or lime for every combining equivalent of phosphoric acid
present in the solution, that is to say, 20 parts of calcium or 28 parts of
lime are left in the solution for every 71 parts of phosphoric acid.
The liquor is then evaporated to dryness, collecting and condensing any a
fumes of hydrochloric acid given off, and the oxalate of lime separated
by dissolving out from it the phosphate of lime present, and by the
evaporation of this solution in suitable vessels to dryness, continuing
and increasing the heat as may be necessary, superphosphate of lime is
obtained.
6. The said solutions of phosphate of lime are also treated by the
addition thereto of phosphoric acid, which is added in such quantity
that the solution after such admixture shall contain phosphoric acid
in the proportion of one equivalent of phosphoric acid for each equivalent
of calcium or lime present, that is to say, sufficient phosphoric acid is
added so as to have 71 parts of phosphoric acid present for every 20
parts of calcium or 28 parts of lime. The solution is then evaporated
to dryness in suitable vessels, the heat continued and increased as may
be necessary, and the dry residue is superphosphate of lime. Any vapours
of hydrochloric acid thrown off during the evaporations are collected and
condensed.
7. To phosphoric acid intermixed with water either lime or oxalate of
lime or any other forms of carbonate of lime, or any of the forms of
phosphate of lime or chloride of calcium, is or are added in such pro-
portion that the solution or mixture shall after such addition contain
one equivalent of lime or calcium for each equivalent of phosphoric acid
present, that is to say, for every 71 parts of phosphoric acid there shall
be either 28 parts of lime or 20 parts of calcium. The solution thus
prepared is evaporated to dryness in suitable vessels, continuing and
increasing the heat as may be necessary, any hydrochloric acid vapours
thrown off being collected and condensed, and the dry residue is super-
phosphate of lime. Superphosphate of lime is sometimes purified by
dissolving it in water, and by subsequent evaporation it is obtained in a
purer
form.
9. When the phosphoric acid has from any cause taken the form
known to chemists as meta-phosphoric acid or pyro-phosphoric acid it
is treated with hydrochloric acid and water or nitric acid and water,
raising the temperature of the mixture for some time, by which means

page_text: it is converted into ordinary (tribasic) phosphoric acid, and it is then
dealt with as already described for the use and treatment of phosphoric
acid. In like manner when these forms of phosphoric acid are in
combination with lime forming the meta-phosphate of lime or the
pyro-phosphate of lime, they are treated with hydrochloric acid and water,
or nitric acid and water, raising the temperature of the mixture for some
time, and the solutions are then dealt with in the same manner as
herein-before described for the production of superphosphate of lime
from solutions of the ordinary forms of phosphate of lime.
15. It is preferred to carry out these processes in the manner specified
and by these means (unless where it is otherwise specified as producing a
slowly soluble superphosphate of lime). Superphosphate of lime is
obtained containing a high per-centage of soluble phosphate of lime; but
if a product yielding a higher per-centage of soluble phosphate of lime
or free phosphoric acid is required, then an increased proportion of
phosphoric acid is allowed to remain in or to be added to the solution
or mixture; but when any smaller per-centage of soluble phosphate of
lime is required or when the superphosphate of lime is required in any
less rapidly soluble condition, then a larger proportion of lime is allowed
to remain in or to be added to the solution or mixture. On this
principle superphosphate of lime is produced in a more or less rapidly
soluble condition, according as the varying requirements of the land may
render most desirable.
SPECIFICATION filed in pursuance of the conditions of the Letters
Patent, and of an Order of the Lord Chancellor, by the said
Benjamin Tanner, in the Great Seal Patent Office on the 27th
November 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
TANNER, of New Brighton, in the County of Chester, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-eighth day of April, in the year
of our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Benjamin Tanner, Her special licence
that I, the said Benjamin Tanner, my executors, administrators, and

page_text: assigns, or such others as I, the said Benjamin Tanner, my executors,
administrators, and assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the 5
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
the Manufacture of SuperPhosphate of Lime," upon the condition (amongst
others) that I, the said Benjamin Tanner, myexecutors or administrators,
by an instrument in writing under my, or their, or one of their hands
and seals, should particularly describe and ascertain the nature of the 1
said Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Seal Patent Office within seven
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Benjamin Tanner, do hereby declare
the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement, that is to say :-
My said Invention consists in certain improvements in the manu-
facture of superphosphate of lime, whereby the same is produced in an
economical manner and in a highly concentrated form, whilst such
control is afforded over its solubility as to enable it to be produced in
such condition that it shall act with great rapidity when applied to the
land or to be more slowly available for the growing crops, according as
the peculiar requirements of any soil may render desirable.
For the convenience of description and reference the following para-
graphs, detailing the processes employed in carrying out my said
Invention are numbered consecutively.
1. Solutions of phosphate of lime in hydrochloric acid are obtained by
taking any of the ordinary forms of phosphate of lime of commerce,
such as phosphorite, coprolites, apatite, phosphatic guanoes, bone ash,
or animal charcoal, or any form of precipitated phosphate of lime or
any other form of phosphate of lime or mixtures thereof which may
be dissolved in hydrochloric acid, using by preference acid varying in
strength from 15° to 20° Twaddell's hydrometer, and having a specific
gravity of from 1.075 to 1.1. The hydrochloric acid is sometimes used
at a temperature of from 80° to 140° Fahrenheit, which it is found
assists the solution of the phosphate of lime considerably. These

page_text: be
solutions are also obtained by passing hydrochloric acid in the gaseous
state through the above-named phosphates, whereby a crystallised.
phosphate of lime is formed, which is removed and manufactured into
superphosphate of lime, or I subsequently flush the phosphate with
water and treat the solution as herein-after described. Solutions are
also obtained by any convenient arrangement of tanks or other suitable
vessels in which any of the above-named varieties of phosphate of lime
or mixtures thereof are placed. These tanks or other vessels may
conveniently arranged with false bottoms made of brick or flagstone
or some similar material, so as to give facilities for draining, running,
or pumping off the liquor. Strong hydrochloric acid is allowed to run
into the tank or vessel and to pass into, over, or through the phosphate,
whereby a crystalline mass is formed from which the liquor remaining
is removed by means of a pump or otherwise, together with any excess
of hydrochloric acid which has not been utilised. On the removal
of the liquor a crystalline mass remains which is dissolved by the
addition of water, and this solution is removed for further treatment,
as described in the paragraph herein contained numbered 3. The dis-
solving out of these crystals having been effected a further quantity
of strong hydrochloric acid is added to any phosphate of lime remain-
ing, and by the use of water the soluble salts formed are again
removed, and this is repeated until the phosphate of lime is exhausted.
I have found that by employing a stronger acid than has been usually
employed an improved result is obtained. It is preferred that the
hydrochloric acid employed for this purpose shall range in strength
from 25° to 30° Twaddell's hydrometer, and shall have a specific gravity
of 1.125 to 1.15, using the stronger acid if the materials treated do not
contain much carbonate of lime. This acid may, however, be employed
of greater or less strength, but the degree of strength herein-before
mentioned will be found well adapted for the purpose. The quantity of
hydrochloric acid used at each charge may be regulated so that the
phosphate is just covered by the acid, but as the phosphate of lime
present becomes more and more exhausted lesser quantities of the acid
should be used, and any acid not utilised is passed on to a second and
similar tank or vessel, usually containing phosphate of lime in a less
advanced stage of exhaustion. In some cases it is desirable that
arrangements should be made for stirring the hydrochloric acid into
the phosphate of lime (preferably in a state of fine division). This may
be conveniently done by having a shaft furnished with stirrers rotating

page_text: in a cylinder into and through which the materials are passed, but
various other mechanical arrangements will accomplish this intermixture.
and I should observe that I do not claim the use of any special apparatus
for such purpose. If the phosphate used contains 70 per cent. of
tribasic phosphate of lime, then for every ton of such phosphate about
thirty-three hundredweight of hydrochloric acid of 30° Twaddell's
hydrometer may be advantageously mixed. The mass should be allowed
to lie in a heap or pit until the crystals are formed, and may then be
put into a tank for the purpose of dissolving out the crystalline phos-
phate. This can be conveniently done by causing water or partially
saturated liquor to pass through the mass by pumping the liquor from
the bottom of the vessel to the surface, and thus establishing a current
through the phosphate, or it may be done by arrangements usually
adopted for lixiviating soda ash, as well understood. Strong solutions
of phosphate of lime are thus obtained, which are treated in the manner
described in the paragraph hereof numbered 3. For obtaining solutions
of any variety of phosphate of lime which contains an admixture of
carbonite of lime it is often convenient to decompose the latter by
adding to the phosphate (previously placed in the tank or vessel in
which it has to be dissolved) sufficient phosphoric acid and water to
dissolve the carbonate of lime present. Thus if a tank contained about ten
tons of phosphate of lime, having in it about five per cent. of carbonite
of lime, the addition of about twenty-three hundredweight and a half
of phosphoric acid of twenty per cent. purity will decompose the
carbonate of lime, forming it into phosphate of lime, and the dissolving
of the entire mass of phosphate by the use of hydrochloric acid may be
proceeded with.
2. I have found that solutions of any of the forms of phosphate of
lime before referred to, or mixtures thereof, may be also obtained in an
improved manner by placing the phosphate in tanks or other vessels,
and adding thereto phosphoric acid and water, so as to allow the
phosphate to be surrounded by or remain in such acid liquor, or by
arranging for the acid liquor to run through the tanks or other vessels.
Thus any carbonate of lime present is converted into phosphate of lime

page_text: of phosphate is gradually dissolved, and in so doing an arrangement
similar to that commonly adopted for lixiviating soda ash accomplishes
the work very satisfactorily. If the phosphoric acid employed is twenty
per cent. of purity, the addition of an equal bulk of water reduces it
to a convenient strength for this purpose, but it may be used with equal
advantage of greater or less strength. Solutions are also obtained by
adding phosphoric acid or phosphoric acid and water to any of the
above-named forms of phosphate of lime or mixtures thereof, whereby
a crystalline mass is formed which is subsequently removed by water.
This may be practically accomplished by charging a tank or other vessel
having a false bottom of brick or flagstone or some similar material
with the phosphate of lime to be dissolved, to which the phosphoric acid
or phosphoric acid and water may be admitted at the top of the tank
and allowed to percolate downwards to the false bottom, or it may be
supplied by means of a tube to the false bottom, so as to percolate
upwards through the phosphate. By this or any other suitable arrange-
ment the phosphoric acid is passed into, over, or through the phosphate
and a crystalline mass is formed, after which any liquor remaining is
drawn or pumped off, and may be passed to another tank or vessel of
phosphate. The crystalline mass formed is a superphosphate of lime
which may be separated and dried for use, or water being passed into
or through the tank dissolves these crystals, and a solution thereof is
obtained which is treated as described in the paragraph herein contained
numbered 3. By repeating the addition of phosphoric acid or phosphoric
acid and water the phosphate is gradually exhausted and got into
solution, as above described. The phosphoric acid employed for this
purpose is found to work satisfactorily when of twenty per cent. purity,
but it can be used of greater or less strength. It is sometimes desirable
to intermix the phosphoric acid or phosphoric acid and water by me-
chanical arrangements, as hercin-before described (but which arrange-
ments form no part of this Invention), in which case about sixty-four
hundredweight of phosphoric acid of twenty per cent. purity may be
mixed with each ton of phosphate of lime containing seventy per cent.
of tribasic phosphate of lime, and the proportion may be generally
regulated according to the strength of the phosphate to be dealt with.
If the phosphate is finely ground the action is more rapid. After the
intermixture has been accomplished the mass may lie in a heap or pit
until the crystals are well formed, and may then be placed in a tank for
dissolving out the crystals, as already described. The solution is then dealt

page_text: with as described in the third paragraph hereof, or the crystalline mass,
which is superphosphate of lime, may be dried for use.
3. Having by the foregoing and by other arrangements obtained
solutions of any of the forms of phosphate of lime or mixtures thereof
in hydrochloric acid, or in phosphoric acid or in mixtures thereof, the
solution is examined and its chemical composition determined (subject
to the principles laid down in the 9th paragraph hereof). It is preferred
to have the phosphoric acid and lime or calcium present in the pro-
portion of 71 of phosphoric for every 28 of lime or 20 of calcium. If
it is found that the lime or calcium present is in excess of the required
quantity, then the solution is dealt with as described in the 4th, 5th,
or 6th paragraphs hereof. If it is found that the phosphoric acid is
in excess of the required quantity, then the solution is dealt with as
described in the 7th paragraph hereof. But if the phosphoric acid and
lime or calcium are present in the required proportion the solution
is passed into large evaporating pans, and heat applied whereby the
solid matter in solution is separated as a superphosphate of lime, and
which may be purified by solution in water and separation of the
insoluble portion by means of water (either by filtration, decantation,
or otherwise), and by subsequent evaporation of the solution to dryness,
by preference avoiding in either case a temperature much above 212°
Fahrenheit, a superphosphate of lime is obtained of a higher quality
and strength, in which case care is always taken to reduce the proportion
of lime or calcium so that there shall be in the superphosphate of lime
so formed less than two equivalents of lime or calcium for each equi-
valent of phosphoric acid present, any excess of lime being undesirable
as producing an inferior product. In other cases the principles laid
down in the following paragraphs are adhered to, and the heat is pro-
longed and increased until the whole or as much as is desired of the
chlorides present is decomposed, and the solid residue is free or as
nearly free as is desired from chlorine, or until hydrochloric acid fumes
cease to be evolved at the temperature employed. These results are
obtained with greater facility by passing superheated steam or hot air in
or over the material, preferably in evaporating pans or furnaces. When
superheated steam is thus employed it is by preference used having a
temperature about 350° Fahrenheit, although the temperature of the
steam may be increased without injury to the product to from 400°
to 450° Fahrenheit; but when hot air or any dry heat is employed for
this purpose it is preferred that such heat should not rise beyond

page_text: 250° Fahrenheit, and although the product is not injured by a tem-
perature below 280° Fahrenheit, mixtures of hot air and steam are
sometimes employed, the temperature at which they are used being
regulated according to the relative proportions in which they are mixed,
but subject to the principles mentioned above. It is also desirable in
some cases, before as well as after the superphosphate of lime is subjected
to the above prolonged and increased temperature, to dissolve the soluble
portion by means of water, and to separate it from the insoluble matter
either by filtration, decantation, or otherwise. This may be done by
various plans, but it is conveniently accomplished with the arrangements
commonly adopted for lixiviating soda ash, or water may be added to
the residue in the evaporating pan, which water is saturated (either
with or without the assistance of heat). In either case the solution thus
obtained is removed for second evaporation, and is treated by either of
the above methods of applying the temperature, according to the con-
dition in which it is desired to obtain the superphosphate of lime, which
is thus formed of a higher strength and quality. Any hydrochloric
fumes thrown off during the evaporation and final decomposition are
conveyed away and condensed by any of the methods used for this
purpose in the general manufacture of hydrochloric acid.
4. To the before-mentioned solutions of phosphate of lime sufficient
sulphuric acid is added to remove all the calcium or lime present, with
the exception of (but subject to the principle laid down in the paragraph
hereof numbered 9) one combining equivalent of calcium or lime for
every combining equivalent of phosphoric acid present in the solution,
that is to say, twenty parts of calcium or twenty-eight parts of lime are
left in the solution for every seventy-one parts of phosphoric acid. If ten
tons of liquor contain ten per cent. of phosphoric acid and ten per cent.
of calcium, the addition of about forty-eight hundredweight of brown
sulphuric acid containing sixty per cent. of anhydrous sulphuric acid (or
an equivalent quantity of any other strength or degree of purity) would
be necessary to remove the excess of lime. The mixture of this liquor
with the sulphuric acid may be conveniently effected in a vat or tank
fitted with a rotating shaft carrying arms or agitators. The sides of
the vat or tank may be fitted with breakwaters to increase the inter-
mixing force of the agitators. The chemical change is completed
without much delay and sulphate of lime is produced; the entire
mixture may be run into a tank fitted with a draining bottom, and the

page_text: sulphate of lime separated, or the mixture may be allowed to settle
and the supernatant liquor run off. In cither case water should be
passed through the sulphate of lime, either of upward or downward
filtration, so as to displace all the original liquor. The clear liquor and
the washings are then subjected to the desired temperature as described
in the paragraph hereof numbered 3, and if thought necessary purified
as therein described, yielding superphosphate of lime.
5. The before-mentioned solutions of phosphate of lime are also
treated by the addition thereto of sufficient oxalic acid to combine with
all the calcium or lime present, with the exception of (but subject to
the principle laid down in the paragraph hereof numbered 9) one com-
bining equivalent of calcium or lime for every combining equivalent
of phosphoric acid present in the solution, that is to say, twenty parts
of calcium or twenty-eight parts of lime are left in the solution for
every seventy-one parts of phosphoric acid. If ten tons of liquor contain
ten per cent. of phosphoric acid and ten per cent. of calcium, the addition
of about forty-five hundredweight of crystallised oxalic acid (or an equi-
valent quantity in any other form or condition) would be necessary to
remove the excess of lime, for which purpose it is convenient for the acid
to be dissolved in water previous to the admixture. The mixture may
be conveniently effected in a mixing vat or tank, and the solid matter
separated as herein-before described in the paragraph hereof numbered 4,
and the liquor will then be ready for running direct to the evaporating
pans and to be subjected to the desired temperature, as described in the
paragraph hereof numbered 3. When it is desired to remove the oxalate
of lime formed in the process, it may be separated after the first evapo-
ration by dissolving out from it the superphosphate of lime produced,
which superphosphate is obtained in a finished condition by a second
evaporation and the treatment described in the paragraph hereof
numbered 3.
6. The before-mentioned solutions of phosphates of lime are also treated
by the addition thereto of phosphoric acid, which is added in such
quantities that the solution after such admixture (but subject to the
principle laid down in the paragraph hereof numbered 9) shall contain
phosphoric acid in the proportion of one equivalent of phosphoric acid a
for each equivalent of calcium or lime present, that is to say, sufficient
phosphoric acid is added so as to have after such admixture seventy-one
parts of phosphoric acid present for every twenty parts of calcium or

page_text: twenty-eight parts of lime. For example, if ten tons of liquor contain.
ten per cent. of phosphoric acid and ten per cent. of calcium, the
addition of about twelve tons and three quarters of phosphoric acid
of twenty per cent. purity will balance the excess of calcium present.
The mixture may be conveniently effected in a mixing vat or tank, such
as described in the paragraph herein numbered 4, and the liquor will be
ready for running direct to the evaporating pans, and to be subjected
to the desired temperature, as described in the paragraph herein num-
bered 3. When the phosphoric acid contains impurities or admixtures
which separate the lime (such as, for instance, sulphuric acid) it is
necessary to make allowance for the lime or calcium which is thus
removed, and proportionately less phosphoric acid should be used. Thus
if the impure or mixed phosphoric acid referred to in the present
paragraph contained ten per cent. of sulphuric acid the quantity to be
used should be reduced to about six tons and three quarters for the
liquor named, and the sulphate of lime formed should be separated as
described in the paragraph herein numbered 4, and the solution and
washings treated as above described.
7. To phosphoric acid or phosphoric acid intermixed with water, or to
solutions of phosphate of lime having an excess of phosphoric acid, either
lime or any of the forms of carbonate of lime, or any of the forms of
phosphate of lime or chloride of calcium or mixtures thereof, is or are
added in such proportion that the solution or mixture shall, after such
addition (but subject to the principle laid down in the paragraph hereof
numbered 9) contain one equivalent of lime or calcium for each equi-
valent of phosphoric acid present, that is to say, for every seventy-one
parts of phosphoric acid there shall be twenty-eight parts of lime or
twenty parts of calcium. For example, if five tons of phosphoric acid of
twenty per cent. purity be used it may be intermixed with about eight
hundredweight of lime, on the same principle the quantity of any of the
above-named lime or calcium compounds or mixtures thereof is regulated,
so that for the same quantity of phosphoric acid there shall be eight
hundredweight of lime or its equivalent of calcium so added. For the
convenience of manufacture it is preferred that the phosphoric acid shall
be reduced in strength by the addition of an equal bulk of water before
the intermixture of the lime. When the phosphoric acid contains
impurities or admixtures which separate lime (such, for instance, as
sulphuric acid) it is necessary to make an allowance for the lime it

page_text: requires, and proportionately more lime should be added; thus if the
phosphoric acid contains ten per cent. of anhydrous sulphuric acid, the
quantity of lime to be used should be increased to about fifteen hundred-
weight, or an equivalent quantity in any of the above-named lime or
calcium compounds. The mixture may be conveniently effected in a
mixing vat or tank, and the sulphate of lime thus formed may be
separated as described in the paragraph hereof numbered 4. The liquor
will then be ready for running to the evaporating pans, and will be
then subjected to the desired temperature, as described in the paragraph
herein numbered 3. But these materials may be intermixed without
the previous addition of water, which, however, may be subsequently
added, or the soluble phosphate may be dissolved out of the mixture
and the liquor evaporated and treated as above described, and the dry
residue will be superphosphate of lime.
8. When the phosphoric acid has from any cause taken the form
known to chemists as metaphosphoric acid or pyrophosphoric acid, it is
readily converted into the condition of ordinary tribasic phosphoric acid
when treated with hydrochloric acid or nitric acid, with or without the
addition of water, and by raising the temperature the action is facilitated.
In carrying this out in practice the metaphosphoric or pyrophosphoric
acid is placed in a tank or vessel, and for every ton of the metaphos-
phoric acid or pyrophosphoric acid an addition is made of about a ton of
hydrochloric acid 15° Twaddell's hydrometer, and the temperature raised
by the aid of steam or hot air, or similar means, under which action these
forms of phosphoric acid are dissolved, and become converted into the
condition of tribasic phosphoric acid, and may be employed and dealt
with as described herein for the use and treatment of phosphoric acid..
In like manner when these forms of phosphoric acid are in combination
with lime, forming the metaphosphate of lime or pyrophosphate of lime,
a similar treatment may be pursued, and solutions thereby obtained from
which superphosphate of lime is manufactured by subjecting it to the
desired temperature, as described in the paragraph hereof numbered 3. If
the phosphate of lime is in the form of pyrophosphate of lime, then about
seventy-seven hundredweights of hydrochloric acid of 15° Twaddell's
bydrometer will be required to dissolve each ton of the phosphate, or
proportionately less if the acid' be of higher strength. If the phosphate
of lime is in the form of metaphosphate of lime, then about fifty
hundredweights of hydrochloric acid of 15° Twaddell's hydrometer will

page_text: be required to dissolve each ton of the phosphate, or proportionately less.
if the acid be of higher strength. The quantity of hydrochloric acid is
varied accordingly as the phosphate may contain mixtures of the meta-
phosphate of lime and pyrophosphate of lime, or any intermediate form
of phosphate. In practice it is quite unnecessary to use the hydrochloric
acid exactly in these proportions, as any excess of the acid is readily
utilised by an addition of ordinary mineral phosphate, or by allowing the
partly saturated liquor to run through tanks containing phosphate,
such as are described in the paragraph hereof numbered 1.
sometimes added to keep the mixture in a fluid condition, and the
temperature is raised as above described, in either case to the resulting
solution, the desired temperature is applied as described in the paragragh
hereof numbered 3.
Water is
9. It is preferred to carry out these processes in the manner specified,
and by these means superphosphate of lime is obtained which contains
a high per-centage of soluble phosphate of lime. If a product yielding
a higher per-centage of soluble phosphate of lime, or free phosphoric
acid is required, then an increased proportion of phosphoric acid is
allowed to remain in or to be added to the solution or mixture; but
when any smaller per-centage of soluble phosphate of lime is required,
or when the superphosphate of lime is required in any less rapidly.
soluble condition, then a larger proportion of lime is allowed to remain
in or to be added to the solution or mixture, which in either case is
treated as herein-before described. On this principle superphosphate of
lime is produced in any more or less rapidly soluble condition, according
as the varying requirements of the land may render most desirable.
should be observed that the proportions of the substances employed for
the purposes of my said Invention are not in all cases precisely such as
are herein-before mentioned, as such proportions may in some instances
be varied without departing from the principles of my said Invention,
as will be well known to and understood by persons conversant with
chemical manufactures and operations.
It
Having thus declared and ascertained the nature of my said Invention,
and in what manner the same is to be performed, I would observe in
conclusion that I do not claim a right to the exclusive use of hydro-
chloric acid in the production of superphosphate of lime, nor the
production of that form of superphosphate of lime which has a com-

page_text: position of one equivalent of acid phosphate of lime combined with one
equivalent of chloride of calcium; but what I claim are,-
-
Firstly. The methods of treating solutions of phosphate of lime such
as are herein described or obtained, and of phosphoric acid in the
manner above set forth, and the production from such solutions or acid
of superphosphate of lime possessed of the more or less rapidly soluble
character desired, substantially as above described.
And, secondly, I claim the methods of treating mixtures of phosphoric
acid or acid phosphate of lime, or mixtures thereof, and chloride of
calcium, in the desired relative proportions, by which means chlorine is 1
expelled, and lime or calcium is combined with phosphoric acid or acid
phosphate of lime, or mixtures thereof, substantially as herein-before
described.
In witness whereof, I, the said Benjamin Tanner, have hereunto set
my hand and seal, this Twenty-seventh day of November, in the 1
of our Lord One thousand night hundred and savants one
Witness,
E. P. H. VAUGHAN,
54, Chancery Lane.
BENJAMIN TANNER. (L.S.)