IMPROVE- MENTS IN THE MANUFACTURE OF HYDRATE OF SODA
Year: 1860

page_text: LETTERS PATENT to William Henry Ralston, of Keele, near Newcastle-
under-Lyme, in the County of Stafford, for the Invention of "IMPROVE-
MENTS IN THE MANUFACTURE OF HYDRATE OF SODA."
Sealed the 16th April 1861, and dated the 22nd November 1860.
PROVISIONAL SPECIFICATION left by the said William Henry Ralston
at the Office of the Commissioners of Patents, with his Petition,
on the 22nd November 1860.
I, WILLIAM HENRY RALSTON, of Keele, near Newcastle-under-Lyme, in
the County of Stafford, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF HYDRATE OF SODA," to be as follows:-
This Invention has for its object improvements in the manufacture of
hydrate of soda. The hydrate of soda of commerce contains as an impurity
a considerable quantity of iron, which causes inconvenience in some of the
manufactures in which the alkali is employed; by this Invention the iron is
separated from the alkali in the course of manufacture. The ordinary process
of manufacturing hydrate of soda is shortly as follows:-The caustic ley is
evaporated to such a strength that in cooling it will deposit a great part of
the foreign salts it contains, and it is allowed to cool for this purpose; the
ley is then poured off and again evaporated, the heat being kept as low as
possible to prevent discoloration of the alkali; the evaporation is continued
until the required amount of concentration is obtained; this is usually 60 per

page_text: cent. of alkali; the material is then put into casks, in which it sets hard, and
in this form it is sent into the market. Now according to this Invention, if it
is desired to obtain a hydrate of soda of great strength, I proceed as here-
tofore by evaporating and separating the foreign salts, but in the course of the
finishing evaporation, in place of keeping the heat low, I continue the
evaporation, and raise the heat until, in the first place, the iron separates as
hydrated peroxide, then I continue the heat until the alkali passes into the state
of dry fusion, and further I still continue the heat until the hydrated oxide of
iron becomes anhydrous; when in this state it will settle to the bottom of the
pot, which it is allowed to do, and the clear alkali is then separated from the
iron. This alkali will be free from iron and of great strength. If so high a
degree of strength is not required the strength may be brought down by
adding common or other salt to the alkali while in a state of dry fusion; it is,
however, preferable in this case not in the first place to separate the foreign salts
from the ley, or only to separate a part of such salts according to the strength
required, so that when the ley is evaporated to bring the alkali to the state
of dry fusion, the same may be of the desired strength, and in order to separate
the iron I proceed as before mentioned.
Also according to this Invention, in place of putting hydrate of soda directly
into the casks in which it is to be packed, and allowing it to set hard therein,
I put it first into separate cooling vessels, and afterwards crush or grind it to
powder, and in this state pack it into the casks; it will then be removed from
the casks more readily, and the wear of the casks will be less.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Henry Ralston in the Great Seal Patent Office on
the 22nd May 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HENRY RALSTON, of Keele, near Newcastle-under-Lyme, in the County of
Stafford, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of November, in the year of our
Lord One thousand eight hundred and sixty, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the said
William Henry Ralston, Her special license that I, the said William Henry
Ralston, my executors, administrators, and assigns, or such others as I, the
said William Henry Ralston, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at all

page_text: 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 Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF HYDRATE OF SODA," upon the condition
(amongst others) that I, the said William Henry Ralston, my executors
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 said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Henry Ralston, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
This Invention has for its object improvements in the manufacture of bydrate
of soda. The hydrate of soda of commerce contains as an impurity a
considerable quantity of iron, which causes inconvenience in some of the
manufactures in which the alkali is employed; by this Invention the iron
is separated from the alkali in the course of manufacture. The ordinary
process of manufacturing hydrate of soda is shortly as follows:-The caustic
ley is evaporated to such a strength that in cooling it will deposit a
great part of the foreign salts it contains, and it is allowed to cool for this.
purpose; the ley is then poured off and again evaporated, the heat being
kept as low as possible to prevent discoloration of the alkali; the evaporation
is continued until the required amount of concentration is obtained; this is
usually 60 per cent. of alkali; the material is then put into casks in which
it sets hard, and in this form it is sent into the market. Now according
to this Invention, if it is desired to obtain a hydrate of soda of great
strength, I proceed as heretofore by evaporating and separating the foreign
salts, but in the course of the finishing evaporation, in place of keeping the
heat low, I continue the evaporation and raise the heat until the iron separates
as oxide of iron, and continue the heat until the alkali passes into the state
of dry fusion, and until the oxide of iron is precipitated to the bottom of the
vessel; the clear alkali is then separated from the iron. This alkali will be
free from iron and of great strength. If so high a degree of strength is not
required, the strength may be brought down by adding common or other salt to
the alkali while in a state of dry fusion; it is, however, preferable in this case
not in the first place to separate the foreign salts from the ley or only to.

page_text: separate a part of such salts according to the strength required, so that when
the ley is evaporated to bring the alkali to the state of dry fusion, the same
may be of the desired strength, and in order to separate the iron I proceed as
before mentioned.
Also according to this Invention, in place of putting hydrate of soda directly
into the casks in which it is to be packed, and allowing it to set hard therein,
put
I
it first into separate cooling vessels, and afterwards crush or grind it
to powder, and in this state pack it into the casks; it will then be removed
from the casks more readily, and the wear of the casks will be less.
And in order that my said Invention may be most fully understood and
readily carried into effect, I will proceed to describe the manner in which I
prefer to conduct the process. I take a crude caustic ley, such as has heretofore
been employed in the manufacture of hydrate of soda, such, for example, as
the red or mother liquor obtained in the manufacture of carbonate of soda, or
it may be a solution of carbonate of soda, rendered caustic by lime, and I
analyse the ley to ascertain the proportion the caustic alkali bears to the whole
solid contents of the ley, including the chloride of sodium, sulphate of soda,
and other salts which are always present in considerable quantities. If the
percentage of alkali thus found is as high as is required in the finished hydrate
of soda, I proceed at once to evaporate the ley, but if this is not so I con-
centrate it, and then set it aside to allow a portion of the salts (which are much
less soluble than the hydrate of soda) to crystallize out; the crystals are
separated from the mother liquor, and thus a sufficient quantity of the salts
are separated to bring up the percentage of caustic alkali to the point required,
and if desired the salts may in this way be almost all removed. I then
evaporate the ley as before, and when the greater part of the water is separated
I keep the temperature sufficiently high to keep the whole perfectly liquid, and
so I continue it until the alkali passes into the state of dry fusion, and until
the iron separates in the manner already described, and is precipitated to the
bottom of the vessel. Upon attaining the stage of dry fusion, I force into the
material, by any convenient appliance, a jet or jets of air until the oxidation of
the sulphurets contained in the fused materials is effected, and when all the
iron has settled down, I, without disturbing the precipitate, pour out the alkali
either into casks as is usual, or if the alkali is to be ground by preference
on to iron plates, so as to form slabs about half an inch thick, which I grind
by preference between millstones in a similar manner to that in which carbonate
of soda is commonly ground, but not quite so fine, and proceed to pack the
same into the casks. Ordinary hydrate of soda cannot advantageously be ground
because it contains uncombined water, and consequently becomes sticky in

page_text: grinding. Hydrate of soda, made as herein described, does not contain un-
combined water, and consequently is ground without difficulty.
With reference to the details of the changes of combination through which
the iron passes (described in my Provisional Specification), I would remark
that such changes may be difficult to prove by reason of the high temperature
required for effecting the changes involved in the process, but it is certain that
by continuing the heat the iron is liberated, and remains suspended in a
flocculent state in the alkali, and by maintaining the heat necessary for the
dry fusion of the material, the iron precipitate becomes granular and settles
to the bottom of the vessel, leaving the fused alkali a clear liquid ready for
packing.
I would also remark that although I have described the separation or
crystallizing out of the salts from the ley only to the extent necessary to.
make alkali of the percentage required, still, if desired, a larger proportion of
the salts may be so separated, and the strength of the alkali afterwards brought
down to the requisite extent by the addition of common salt, when the alkali
is in the state of dry fusion, or the salts previously separated by crystallization
or other salts may be substituted for common salt, or the strength may be
brought down by the addition of salts during the grinding.
The process above described is applicable for the purification and concen-
tration of hydrate of soda made by the ordinary process, the same being
brought to a state of fusion, and treated as before described.
In witness whereof, I, the said William Henry Ralston, have hereunto
set my hand and seal, this Eighteenth day of May, in the year of
our Lord One thousand eight hundred and sixty-one.
WILLIAM HENRY RALSTON. (L.S.)