IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES OF SODA AND OTHER ALKALINE BASES
Year: 1871

page_text: LETTERS PATENT to Benjamin Tanner, of New Brighton, in the
County of Chester, Manufacturing Chemist, for the Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF PHOSPHATES OF SODA AND OTHER
ALKALINE BASES.”
COMPLETE SPECIFICATION filed by the said Benjamin Tanner at the
Office of the Commissioners of Patents, with his Petition and
Declaration, on the 30th December 1871, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
TANNER, of New Brighton, in the County of Chester, Manufacturing
Chemist, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
THE MANUFACTURE OF PHOSPHATES OF SODA AND OTHER ALKALINE BASES," and
have petitioned Her Majesty to grant unto me, my executors, adminis-
trators, and assigns, Her Royal Letters Patent for the same, and have

page_text: made solemn Declaration that I am the true and first Inventor
thereof.
NOW KNOW YE, that I, the said Benjamin Tanner, do hereby declare
that the following Complete Specification, under my hand and seal,
fully describes and ascertains the nature of the said Invention, and in 5
what manner the same is to be performed, in and by the following
statement, that is to say:-
It is a well-known fact, which has been described in standard
chemical works published many years prior to the date of my
application for the above-mentioned Letters Patent, that acid phosphate 1
of soda may be produced in the following manner :-"One atom of
phosphoric acid heated with common salt, unites with only one atom of
soda and with two atoms of basic water, forms this salt," namely, acid or
mono-phosphate of soda. From the acid phosphate of soda the other
forms of phosphate of soda are obtained by various well-known 1
processes.
My present Invention consists of further improvements which have
been made by me, and are based upon those for which I applied for
Letters Patent on the Fifth day of June 1871, numbered 1489.
use.
I have discovered that by the use of the improved processes of 2
manufacture herein-after described, I am able to produce acid phosphate
of soda and other forms of phosphate of soda much more efficiently
and economically than by any of the processes heretofore known or in
The employment of chloride of sodium or common salt has been
hitherto attended with difficulties owing to the fact that the temperature
which was considered necessary to decompose more than one equivalent
of chloride of sodium displaced the basic water, thereby forming pyro-
phosphate of soda or mixtures of meta-phosphate and pyro-phosphate of
soda. This necessitated the use by the operator who desired to produce
the other forms of phosphate of soda of the more expensive sources of
soda in the form of caustic soda, or carbonate of soda, or sulphate of
soda. By the present Invention I am enabled to obviate the difficulties
above mentioned by submitting in the manner herein-after described the
materials which are employed to the action of steam, superheated steam,
or mixtures of steam and hot air, or mixtures thereof, with or without
the assistance of heat applied to the bottom of the furnace in which the
operation is carried on, whereby the decomposition is accomplished more
perfectly and with greater facility, less expensive materials being

page_text: available for the manufacture, and the difficulty herein-before referred
to is conveniently overcome.
It will be seen that the materials operated upon are those which have
been as is well known previously used, and which are for the most part
mentioned in the Provisional Specification deposited with my previous
application for Letters Patent of the Fifth day of June 1871 above
referred to, but the mode of operating upon them and in particular the
use of the steam, superheated steam, or mixtures of steam and hot air,
or mixtures thereof, herein-after described, will, as I have discovered,
produce far more beneficial results than could have been obtained by
the processes described in my said Provisional Specification, or by any
other process with which I have hitherto been acquainted.
For the convenience of reference the several portions of this Specifica-
tion will be consecutively numbered.
1. For the production of mono-sodic phosphate (having a composition
of one equivalent of soda, two equivalents of basic water, and one
equivalent of phosphoric acid, with or without water of crystallization)
phosphoric acid is mixed with chloride of sodium in such proportions
that one equivalent of phosphoric acid shall react upon one equivalent
of chloride of sodium, and for this purpose it is preferred to use 71 cwts.
of phosphoric acid with about 58 cwts. of chloride of sodium. These
materials may be used in a more or less pure condition. In practice
they may be mixed in the proportion of 355 cwts. of commercial phos-
phoric acid containing 20 per cent. of phosphoric acid and about
65 cwts. of common salt containing 90 per cent. of chloride of sodium.
This operation may be performed in any convenient vessel in which the
temperature can be casily raised, but furnaces made of fire-clay or
constructed in a similar manner to those employed in the manufacture
of soda ash are preferred for this purpose. In order to effect the
evaporation of the mixture I employ currents of steam or mixtures of
steam and hot air or superheated steam or mixtures thereof. These
currents are made to pass over, into, or through the mixture or mixtures
acted upon either with or without the employment of additional heat
applied to the bottom of the furnace in which the operation is
performed, and the heat is continued to be applied until acid fumes
cease to be thrown off. When superheated steam is used to effect the
required decomposition, the temperature of the steam may safely be
raised to 350° or 400° Fahrenheit, and in some cases the temperature

page_text: may be increased to 450° Fahrenheit without injury to the product
obtained. When mixtures of hot air and steam are employed for this
purpose the requisite temperature is regulated according to the propor-
tion in which the steam and hot air are mixed. Thus the temperature
of the mixture of hot air and steam should be lowered from that above
named down to about from 220° to 250° Fahrenheit as the proportion of
steam in the mixture is decreased. The above-named materials may be
mixed in a reverberatory furnace and treated in the same way as that by
which sulphate of soda is commonly made, simply substituting phos-
phoric acid in the proper proportion (which would be well known) for
the sulphuric acid employed in such manufacture, and in making use
of the ground heat supplied (which it is preferred should not rise beyond
280° Fahrenheit) in conjunction with mixtures of steam and hot air, or
superheated steam, or steam, or mixtures thereof. The temperature
should be controlled within the desired limits as already described. I
have found that the use of either superheated steam, or mixtures of
hot air and steam, or steam, or mixtures thereof, by passing the same
into, over, or through the material as above described, very much assists
the liberation of the acid fumes (which is usually continued till they
cease to be evolved), and tends to make the decomposition com-
paratively more rapid and perfect. The fumes thrown off are condensed
or utilised by well-known processes, and which form no part of my said
Invention. The mono-sodic phosphate produced by either of the fore-
going processes is sometimes dissolved by means of water, and may be
evaporated or crystallized by any of the methods now employed for such
purpose, or purified by other convenient and usual arrangements.
2. When it is desired to produce bi-sodic phosphate (having a
composition of two equivalents of soda, one equivalent of basic
water, and one equivalent of phosphoric acid, with or without water
of crystallization) the only variation from the processes described in
the paragraph hereof numbered 1, which is necessary, is an increase
in the quantity of chloride of sodium, which for this purpose should
be added in double the proportion named therein, that is to say, for
355 cwts. of commercial phosphoric acid containing 20 per cent. of
phosphoric acid, about 130 cwts. of common salt containing 90 per cent.
of chloride of sodium would be required. The higher temperature by
the use of steam or superlicated steam, or mixtures of hot air and
steam, or mixtures thereof, as described in paragraph hereof numbered 1,

page_text: is preferred, and when necessary the bi-sodic phosphate is purified as
herein-before described.
3. When tri-sodic phosphate (having a composition of 3 equivalents
of soda and one of phosphoric acid with or without water of crystalliza-
tion) is required, cither of the processes described in the paragraph
hereof numbered 1 is adopted (using by preference the higher tem-
perature herein-before described), with an increase in the quantity of
common salt, which should be as nearly as is practicable 3 times the
quantity named in the last-mentioned paragraph, that is to say, for
355 cwts. of commercial phosphoric acid containing 20 per cent. of
phosphoric acid, about 195 cwts. of common salt containing 90 per cent.
of chloride of sodium would be necessary.
In some cases at the stage of the process when acid fumes cease to
come off, the product may be subjected to heat gradually increased to
a red heat with or without the continued application of steam or super-
heated steam, or mixtures of hot air and steam, or mixtures thereof, in
the manner already described, so as to displace any chlorine remaining.
The tri-sodic phosphate obtained by either of the foregoing processes
may be purified by the methods of purification ordinarily used as
herein-before- described.
When the phosphoric acid employed in either of the foregoing
processes contains any acid capable of decomposing chloride of sodium
(such as sulphuric acid) either as an impurity or admixture, a larger
quantity of chloride of sodium will be required. If the phosphoric acid
contained 10 per cent. anhydrous sulphuric acid, either as an impurity
or admixture, then 10 tons of such acid would contain 1 ton anhydrous
sulphuric acid, and would require about 33 cwts. of commercial chloride
of sodium of 90 per cent. purity in addition to the quantity required for
the phosphoric acid. The sulphate of soda so formed may either be
allowed to remain in the product or be separated by crystallization, or
by any convenient arrangement.
4. The proportions in which the materials are mixed should as is well
known be regulated by their purity and strength, and by the condition
or form in which it is desired to obtain either of the phosphate of soda,
but for economical working it is preferred to use the phosphoric acid in
the proportion of one equivalent of phosphoric acid to one, two, or three
equivalents of soda, and by increasing and continuing the temperature

page_text: in the manner described, mono-sodic, bi-sodic, or tri-sodic phosphate
can be efficiently and very economically produced. For the convenience
of manufacture it is preferred to add the required quantity of phosphoric
acid and chloride of sodium by one and the same operation, but it is
evident that the same end may be attained by successive additions at
different stages of the operation, and also by regulating the proportion
of chloride of sodium employed mixtures of any of the foregoing
phoshates can be obtained. By means of the foregoing treatment and
on the same principle mono-sodic or bi-sodic phosphate, or meta-
phosphate or pyro-phosphate of soda, or mixtures thereof, can be made
to react on chloride of sodium for the production of any of the before-
named phosphates of soda by regulating the proportion of the mixture
according to the product desired.
In some cases it is found advantageous to intermix with the mass
either before or after evaporation coke or pumice stone, or some similar
material, preferably in small lumps, and then proceed in the manner
already described.
When the decomposition is completed the mass may be lixiviated
by any suitable arrangement, and the phosphate of soda obtained in the
manner described in the paragraph hereof numbered 1. The coke or
pumice stone or other materials can be again employed for a similar
purpose, or the mixture may be reduced to powder without separation
of the coke or pumice stone. The coke or pumice stone or similar
materials so employed divides the mass and keeps the mixture more
open to the action of the steam or superheated steam, or mixtures of
steam and hot air, and thus facilitating the completion of the process.
5. The process of manufacture above described for producing phos-
phates of soda are employed in the production of phosphates of other
alkaline bases (such as potash or ammonia) by the employment of the
chloride of either of the other alkalies, these being treated in the same
manner as has been herein described for chloride of sodium, and the
proportions in which they are used being varied according to their
respective equivalents or combining proportions, which are well known
to chemists and recognised in manufacturing processes. In like manner,
and on the same principle, phosphates having more than one alkaline
base may be produced by using in the manner herein described a
mixture of the said bases, or of the aforesaid compounds thereof,

page_text: instead of using a single base or any of the before-mentioned compounds
thereof.
It 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, as will be well
known to persons experienced in the manufacture of analogous chemical
products, in some instances be varied without departing from the
principles of my said Invention.
Having thus described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I would
observe in conclusion, that what I consider novel and original, and
therefore claim as constituting the Invention intended to be secured
to me, are,-
First. The production of mono-sodic, bi-sodic, or tri-sodic phosphates,
or mixtures thereof, by the aid of currents of steam, or superheated
steam, or mixtures thereof, with heated air in the manner herein-before
substantially described and set forth.
Secondly. The production of the corresponding salts of potash or of
ammonia by the aid of currents of steam, or superhcated steam, or
mixtures thereof, with heated air, in the manner hercin-before sub-
stantially described and set forth.
And, thirdly. The production of tri-basic phosphates having more
than one of the before-mentioned alkalies (namely, soda, potash, or
ammonia) as bases thereof, by the aid of currents of steam or super-
heated steam, or mixtures thereof, with heated air in the manner
herein-before substantially described and set forth.
In witness whereof, I, the said Benjamin Tanner, have hereunto
set my hand and seal, this Twenty-eighth day of December, in
the year of our Lord One thousand eight hundred and seventy-
one.
BENJAMIN TANNER. (L.S.)