IMPROVEMENTS IN THE MANUFACTURE OF SOLUBLE PHOSPHATE OF LIME
Year: 1871

page_text: LETTERS PATENT to John Thomas Way, of No. 9, Russell Road,
Kensington, in the County of Middlesex, for the Invention of
“IMPROVEMENTS IN THE MANUFACTURE OF SOLUBLE PHOSPHATE OF LIME."
Sealed the 29th December 1871, and dated the 14th July 1871.
COMPLETE SPECIFICATION filed by the said John Thomas Way at
the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 14th July 1871, pursuant to the 9th Section of
the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
THOMAS WAY, of No. 9, Russell Road, Kensington, in the County of
Middlesex, send greeting.
WHEREAS I am in possession of an Invention for “IMPROVEMENTS IN
THE MANUFACTURE OF SOLUBLE PHOSPHATE OF LIME," and have petitioned Her
most Excellent Majesty Queen Victoria to grant unto me, the said John
Thomas Way, my executors, administrators, and assigns, Her Royal
Letters Patent for the same, and have made solemn Declaration that I
am the first and truc Inventor thereof.

page_text: NOW KNOW YE, that I, the said John Thomas Way, do hereby
declare the nature of the said Invention to be as follows:-
Heretofore it has been usual to employ in the manufacture of super-
phosphate of lime oil of vitrol or sulphuric acid to render soluble the
phosphate of lime, which it does by combining with a part of the lime
forming gypsum, which is practically insoluble and remains without
inconvenience in admixture with the soluble phosphate. It has not
been practicable to use hydrochloric acid in place of sulphuric acid in
this manner, because the mixture if so made would be delequescent and
unfit for the ordinary purposes of manure from its containing free or
uncombined chloride of calcium.
Now this Invention consists of different methods of employing hydro-
chloric acid in conjunction with sulphuric acid in such manner that an
article of high quality and free from the objection above named is
obtained more economically than by the use of sulphuric acid alone.
The methods to be described depend upon the production of a com-
pound of acid or mono-phosphate of lime with chlorido of calcium in the
proportion of one equivalent of each. This salt, which I call chloro-
phosphate of lime, was discovered by myself several years ago; it is
practically non-deliquescent.
If a phosphate of lime were met with in nature consisting of one
equivalent of phosphoric acid united with two equivalents of lime it
would suffice with such a phosphate to dissolve it in hydrochloric acid
and evaporate to dryness to obtain the salt above mentioned. During
the evaporation the phosphoric acid would decompose one half or onc
equivalent of the chloride of calcium present with the escape of an
equivalent of hydrochloric acid and the formation of mono-phosphate of
limo, which would unite with the rest of the chloride of calcium to form
"chloro-phosphate of lime." But it so happens that ordinary phosphate
of lime contains three equivalents of lime to one equivalent of phosphoric
acid, and a solution of this when evaporated gives an equivalent of
chloride of calcium in addition to that which can combine with acid
phosphate of lime; this additional equivalent renders the product
deliquescent and practically unfit for manure.
Now the object of the processes to be described is to adjust the
balance between the lime and phosphoric acid so as to reduce the
chloride of calcium left in the product to one equivalent for each
equivalent of phosphoric acid; and it is manifest that this can be done

page_text: by decreasing the quantity of lime or by increasing the proportion of
phosphoric acid.
I shall shortly recapitulate the methods by which I accomplish this
object.
I dissolve mineral phosphate of lime, burnt bones, or other substances
consisting principally or largely of phosphate of lime in hydrochloric
acid of any convenient strength, preferring however a solution of this
acid of sixteen degrees Twaddle or sixteen per cent. real acid.
solution of phosphate so made, which I shall call "the liquor," I deal
with in one or other of the following ways:—
The
And in order to a more casy comprehension of the subject I will in
the first instance suppose that the liquor contains phosphoric acid and
limo in the proportion of one equivalent or combining proportion of
the former to three equivalents or combining proportions of the latter.
Where carbonate of lime has existed in the mineral or other phosphato
of lime the proportion of lime will be greater than this, but to this I
will afterwards refer.
The following are methods of reducing the proportion of lime so as to
produce chloro-phosphate of lime as the product :-
A. Adding sulphuric acid to "the liquor," separating by filtration
the sulphate of lime produced, and evaporating to dryness.
B. Adding sulphuric acid as in A. and evaporating the whole to
dryness without separation of the sulphate of lime.
C. Evaporating the liquor to dryness, mixing the product with
sulphuric acid, and drying up the mixture by heat.
The product in A. is "chloro-phosphate of lime" with some insoluble
phosphate produced in the evaporation.
In B. and C. the chloro-phosphate is mixed with sulphate of time.
D. Evaporating the liquor till crystals of chloro-phosphate form, sepa-
rating the crystals and adding to them sulphuric acid to decompose the
adhering chloride of calcium, and drying up the mixture or dissolving
the crystals and recrystallizing.
In all these processes sulphate of soda may be substituted for sulphuric
acid, but at an increase of cost and a diminution in the quality of the
product.
By all of the above methods a portion of the base is cither rendered
insoluble or removed.

page_text: The methods of increasing the quantity of phosphoric acid in lieu of
diminishing the quantity of base consist in substituting for the sulphuric
acid phosphoric acid or acid phosphate of lime in the processes above
set forth, the whole of the base is thus converted into chloro-phosphate.
Without dissolving the phosphate of lime, in the first instance, in
hydrochloric acid I sometimes add to powdered phosphate of lime
sulphuric and hydrochloric acid in such proportions as to form sulphate
of lime and chloro-phosphate of lime, and I dry up the products for usc.
Having thus recapitulated the processes which form the subject of the
present Patent, and each of which may in particular circumstances
possess advantages, I proceed to describe more particularly the way in
which they should be carried out.
Process A. I take any convenient quantity of "the liquor" prepared
in the manner already described, and having ascertained by chemical
analysis how much phosphoric acid and lime it contains, I add to it such
quantity of oil of vitriol, "brown acid," or other form of sulphuric acid
as shall be sufficient to unite with one-third of the lime present in "the
liquor." For instance, I take one hundred gallons of the liquor, and
having found that this quantity contains seventy-one pounds of phos-
phoric acid and eighty-four pounds of lime (which are the chemical
equivalents in pounds in tri-phosphate of lime) I add forty-nine pounds
(or one equivalent in pounds) of oil of vitriol, or a corresponding
quantity of "brown acid," this quantity being capable of uniting with
twenty-eight pounds or one-third of the lime present. I mix tho
sulphuric acid and the liquor by agitation, and by means of filtration
through cloth or otherwise I separate the sulphate of lime which has
been produced by the addition of the sulphuric acid, which sulphate of
lime I wash by successive quantities of water. The solution so obtained
and the washings contain the phosphoric acid and two-thirds of the lime
originally present in the liquor. I evaporate theso liquids in a rever-
beratory furnace or other convenient arrangement to a thick paste,
collecting and condensing the vapours of hydrochloric acid which are
given off during the process, and I further dry it up by steam or other
heat, avoiding a temperature much above two hundred and twelve
degrees Fahrenheit.

page_text: quantity is not objectionable (except on the ground of unnecessary
expense), provided that it does not exceed twice the above amount
When the liquor, as is frequently the case, contains more than
84 parts of lime to 71 parts of phosphoric acid I use an additional
quantity of sulphuric acid for such excess in the proportion of 49 lbs. of
oil of vitriol (or a corresponding quantity of "brown acid" or other
strength of sulphuric acid) for every such additional 28 lbs. of lime
present. For instance, supposing that in 100 gallons of liquor containing
71 lbs. of phosphoric acid I find 98 lbs. of lime instead of 84 lbs., then
in addition to 49 lbs. of oil of vitriol, as in the previous instance, I
require to use 24 more to deal with the excess of 14 lbs. of lime present
in the liquor.
Practically it is generally known without chemical analysis what
the nature of the liquor is by that of the raw phosphate from which
it was produced, and the sulphuric acid necessary may readily be
calculated.
In the final evaporation or drying up of the product I prefer to keep
the temperature as little above 212° Fahrenheit as may be. Never-
theless the product is not destroyed at a temperature of 280° or 300°
Fahrenheit, but at such temperature a larger proportion of the soluble
phosphate becomes insoluble.
Process B. This mothod is carried out essentially as in the case of A,
with the exception that the sulphate of lime remains in the product,
which is not therefore of such high quality as regards per-centage of
soluble phosphate as in the other process.
Process C.--In this process I evaporate the liquor without addition of
sulphuric acid, and the drying may with advantage be effected at a
higher temperature than in A and B, namely, at 300° F., or even higher.
With the dry product I mix sulphuric acid by suitable mechanical
means, subsequently heating the mixture to 212° or thereabouts to expel
hydrochloric acid. The quantity of sulphuric acid to be used in this
caso can be calculated in the same way as in processes A. and B., the
calculation being based on the quantity of liquor evaporated, or the dry
residue may be examined for the proportion of phosphoric acid and lime
contained in it, and the sulphuric acid calculated as in the other cases.
D. This process somewhat differs from that before described inasmuch
as the chloro-phosphate of lime is removed from the excess of chloride of
calcium in great part by crystallization instead of the excess of chloride

page_text: C
.
of calcium being separated from the chloro-phosphate entirely by
chemical agency. I evaporate "the liquor" till it begins to shew signs.
of crystallization. I allow it to cool, and I separate the crystals from the
mother liquor by drainage and pressure.
I ascertain the quantity of chloride of calcium present in the crystals &
over and above the proper quantity to form chloro-phosphate, and I add
an equivalent of sulphuric acid, or acid phosphate of lime, or half an
equivalent of phosphoric acid for each equivalent of chloride of calcium
in excess, and dry up the product at 212° F. or thereabouts, or I add
the sulphuric acid in any additional quantity up to such quantity as is 1
sufficient to decompose the whole chloride of calcium present, driving
off the hydrochloric acid by heat, but in this case the product is no
longer chloro-phosphate of lime, but a mixture of acid phosphate of
lime and sulphate of lime, similar to that made by decomposing diphos-
phate of lime by sulphuric acid.
In dealing with the liquor for crystallization as now described I some-
times add before evaporation lime or chalk to neutralize free acid, by
which the liberation of hydrochloric acid fumes is avoided. The chalk
or limo is added so long as it dissolves in the liquor.
When dealing with the liquor by increasing the proportion of phos-
phoric acid in relation to the lime, I obtain the acid phosphate of lime
for the purpose from ordinary superphospate of lime, made by the action.
of sulphuric acid on phosphate of lime. The phosphoric acid is obtained
by using an additional equivalent of sulphuric acid in excess of that
employed in the manufacture of superphosphate of lime.
I will give an example. I take 100 gallons of liquor, in which I will
suppose as before that the relation of the lime to the phosphoric acid is
as 3 to 1 in equivalents, and that the 100 gallons contain 71 lbs. of
phosphoric acid and 84 lbs. of lime. To this I add so much of acid
phosphate of limo as will contain 71 lbs. or an equivalent in pounds of
phosphoric acid, that being the quantity of phosphoric acid in the state
of acid phosphate of lime which will combine with the equivalent of
chloride of calcium in excess, or I add so much of a solution of phosphoric
acid as will contain 35 lbs., or half an equivalent in pounds of phos-
phoric acid, that being the quantity of uncombined phosphoric acid
which will convert the chloride of calcium into chloro-phosphate.
I evaporate the solution to dryness as before. The product being
practically chlorc-phosphate of lime, if the liquor contains an excess

page_text: -
of lime beyond the three equivalents, I increase the quantity of acid.
phosphate or of phosphoric acid accordingly in the manner described
in using sulphuric acid. Instead of using solutions of phosphoric acid
or acid phosphate I sometimes employ the superphosphate itself, and
mix it directly with the liquor, but in that case the product is of lower
quality.
It is also evident that the two processes of reducing the proportion
of lime by sulphuric acid, &c., or increasing the proportion of phosphoric
acid by its addition or that of acid phosphate of lime may be practised
conjointly if any advantage is derivable from such a plan.
When I treat the raw insoluble phosphate without in the first instance
preparing a liquor by dissolving it in hydrochloric acid, I proceed as
follows: I take powdered mineral or other phosphate, and having ascer-
tained the proportion of tri-phosphate of lime and of carbonate of limo
in it, I calculate, first, what quantity of sulphuric acid is necessary to
decompose the carbonate of lime, and what quantity will be required to
unite with one out of every three parts of the lime present as phosphate.
I also calculate how much hydrochloric acid is necessary to unite with
an equal quantity of lime. For instance if the raw phosphate to be
used contains 70 per cent. of tri-phosphate, of lime and 10 per cent.
of carbonate of lime, 221 lbs. will contain 71 lbs. or one equivalent in
pounds of phosphoric acid and 22.1 lbs. of carbonate of lime. For this
quantity of carbonate of lime I shall require 21-7 lbs. of oil of vitriol,
and for a third part or one equivalent of the lime 49 lbs. oil of vitriol,
or in all about 71 lbs., whilst of hydrochloric acid of 30° Twaddle or 30
per cent. I shall require 119 lbs.; that being the quantity of acid of
this strength which contains one equivalent in lbs. or 36 lbs. of real
hydrochloric acid.
I mix the raw phosphate with the acids by any convenient mechanical
arrangement, and allow the mixture to lic for a time for completion of
the chemical action, if necessary I finally dry the product on hot floors
or otherwise at a heat not much exceeding 212° F. From this product,
which is a mixture of chloro-phosphate of lime with sulphate of lime and
the impurities of the raw phosphate, I may obtain the chloro-phosphate
by treatment with water and evaporation of the solution.
In the foregoing description I have provided for the giving off of
hydrochloric vapours during evaporation of the liquors; this acid would
be condensed in the usual way practised in alkali works.
But by a

page_text: modification of the process such production of hydrochloric acid can be
avoided whon desirable. When mineral phosphate of lime is dissolved
in hydrochloric acid the liquor is usually a mixture of free phosphoric
acid with chloride of calcium, but prolonged contact with the phosphate
causes this phosphoric acid to pass into the state of acid phosphate of
lime by solution of a further quantity of phosphate of lime, and in
this state the liquor will consist of one equivalent of acid phosphate
of lime mixed with two equivalents of chloride of calcium. If to this
liquor acid phosphate of lime from ordinary superphosphate of lime
(or the superphosphate itself) is added in proper quantity (that is to
say, one equivalent for each equivalent of chloride of calcium in excess)
and the liquor evaporated, chloro-phosphate of lime will be produced.
without the formation or escape of hydrochloric acid. The same result
will be obtained if to a liquor of the composition described sulphate
of soda is added, and the sulphate of lime produced may either be
separated before evaporation or may form part of the final product.
The chloro-phosphate of limo manufactured as above described is
valuable for use as manure either alone or mixed with other substances,
or it may be used in the arts as a source of phosphoric acid.
Having thus described the nature of my said Invention, and the
manner of performing the same, I would have it understood that I
claim the manufacture of soluble phosphate of lime in the state of
chloro-phosphate (either for use as such or for further treatment) by
acting on the insoluble or natural phosphate with hydrochloric acid,
preventing the preponderance of chloride of calcium by converting a
portion of the base into sulphate or by the addition of a further quantity
of phosphoric acid or acid phosphate of lime.
I also claim the processes herein set forth, substantially as described.
In witness whereof, I, the said John Thomas Way, have here-
unto set my hand and scal, this Fourteenth day of July, in
the year of our Lord One thouand eight hundred and seventy-