CERTAIN IMPROVEMENTS IN THE MANUFACTURE OF POTASH AND SODA, ALUMS, SULPHURIC ACID, AND SULPHATE OF SODA
Year: 1844

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
BIRKMYRE, of Millbrook, in the County of Cornwall, Chemist, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Nineteenth day of September, in the eighth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
William Birkmyre, Her especial licence, full power, sole privilege and authority,
that I, the said William Birkmyre, my exors, adññiors, and assigns, or such
others as I, the said William Birkmyre, my exors, admors, or assigns, should
at any time agree with, and no others, from time to time and at all times.
during the term of years therein expressed, should and lawfully might make,
use, exercise, and vend, within England, Wales, and the Town of Berwick-
upon-Tweed, my Invention of "CERTAIN IMPROVEMENTS IN THE MANUFACTURE OF
POTASH AND SODA, ALUMS, SULPHURIC ACID, AND SULPHATE OF SODA;" in which
said Letters Patent is contained a proviso that 1, the said William Birkmyre,
shall cause a particular description of the nature of my said Invention, and in
what manner the same is to be performed, to be inrolled in Her said Majesty's
High Court of Chancery within six calendar months next and immediately
after the date of the said in part recited Letters Patent, as in and by the
same, reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
William Birkmyre, do hereby declare that the nature of my Invention, and

page_text: the manner in which the same is to be performed, is described and ascertained
as follows (that is to say) :-
The ordinary practice at present of manufacturing sulphuric acid (oil of
vitriol) is either burning sulphur in peculiar furnaces (termed sulphur burners),
which are commonly arranged in pairs, or iron pyrites (mundic) in kilns,
In either case it is usual in
also generally arranged in the same manner.
about every two hours to put into a cast-iron pot (nitre pot), supported a few
inches above the burning sulphur or iron pyrites, about one eighth of the
weight of the sulphur of nitrate of potash (saltpetre), or about one ninth of
nitrate of soda (cubic nitre), to pour over either of these salts about three
fourths its weight of sulphuric acid, specific gravity 1750.
The gaseous
products, consisting chiefly of sulphurous acid and oxides of nitrogen, are
conducted into large leaden chambers, the bottoms of which are covered
to the depth of several inches with water, and which chambers are also
supplied of late years with a small current of steam, which has been found to
augment materially the produce of acid.
Now the object of my Invention is,-
First, the application of a substance to prolong the disengagement of the
oxides of nitrogen, and which at the same time shall serve in the production of
potash or Soda alum.
Secondly, to decompose substances containing potash and alumina, or soda
and alumina, by the action of heat and sulphuric acid, or by the combined
action of heat, sulphuric acid, with a salt of potash or of soda, to form a salt
of alumina in vessels contained within sulphur burners or pyrites kilus, and to
condense the volatilized sulphuric acid in vitriol chambers.
Thirdly, to produce sulphate of soda (Glauber's 'salts or salt ceake) by
decomposing a solution of soda alumn by'a salt of potash into potash alum
and sulphate of soda. I have found by experience that clay, particularly
porcelain or Cornish clay, is the best agent that can be employed to prevent
the too rapid disengagement of the oxides of nitrogen from the nitrates of
potash or soda, when they are strongly heated with sulphuric acid, and to
produce at the same time either potash, sulphate of alumina (common alum);
by the decomposition of nitrate of potash or soda, sulphate of alumina (soda
alum), by the decomposition of nitrate of soda.
*.ted.
I now proceed to state the manner in which I would recommend it to
be used. First, for one ton (2240 lbs.) of coarsely-powdered crystals of
nitrate of potash, mix sixteen liundred pounds in' powder of dry Cornish clay,
Take of this mixture every two hours eighteen pounds for a vitriol chamber,
making a ton and a half (3360 lbs.) per diem of sulphuric acid, specific.

page_text: gravity 1848, and put it into a nitre, pot, pour in and stir fourteen pounds, of
sulphuric acid, specific gravity 1750.,,Then place the nitre pot and its
.contents a few inches above, the, burning sulphur of a pyrites kiln, when,
by, the action of heat and sulphuric acid, the oxides of nitrogen begin
gradually to escape into the chamber, and the mixture (nitrate of potash
and clay) is thereby converted into a species of burnt alum. The nitre
and its contents should be withdrawn from the kiln at the end of four hours.
By operating in this manner three, thousand and fifty-five pounds of sulphuric
acid, specific gravity 1848, has been obtained from one ton (2240 lbs.) of iron
pyrites, with eighty-four pounds, of nitrate of potash (in one hundred and
forty-four pounds of the said mixture) and one hundred and twelve pounds
of sulphuric acid, specific gravity 1750. The product, in the nitre pot
generally weighs twenty-two. pounds, and yields on simply lixiviating with ten
per cent. of sulphuric acid two and a half times the weight of the nitrate
of potash employed (or fully one half of what it is capable of yielding) of
potash alum (common alum). But it is evident from what I have set forth
in the preceding part of this Specification that this process admits of variety
in its application; for instance, if ten pounds and a half of nitrate of potash be
taken with fifteen pounds of Cornish clay and twenty pounds and a quarter of
sulphuric acid, specific gravity 1750, the whole of the potash might be
converted into potash alum; but I prefer resorting to the following operation
to convert the whole of the potash into potash alum. Secondly, take twenty-
five pounds in powder of dry. Cornish clay and place it in a large nitre
pot, pour in and stir thirty-seven pounds of sulphuric acid, specific gravity 1750,
let the nitre pot and its. contents be placed, as before, above the, burning
sulphur of a pyrites kiln, and. at the end of four hours it should be withdrawn.
Or, instead of thirty-seven pounds of sulphuric acid, specific gravity 1750,
sixty pounds of sulphuric acid, specific gravity 1400, may be stirred with the
clay in a cast-iron vessel lined on the inside with. porcelain; the product
arising from, the weaker sulphuric acid is nearly the same as that from
-the stronger acid, with the advantage of dispensing entirely with steam for a
chamber from a steam boiler.. The greater part of the sulphuric acid in both
instances by the action of heat combines with the alumina and potash or.
soda of the clay. forming, chiefly. a sesquisulphate of alumina. Take of the
substance so prepared one hundred and sixty-eight pounds, and three hundred
and thirty-six-pounds of the product from the nitrate of potash and clay, and
lixiviate with sixty-seven pounds of sulphuric acid, specific gravity 1400. The
lixiviating vessel should be of lead, and placed over the flue of a reverberatory
furnace of the usual size for making alkali. The heat from such a furnace is

page_text: sufficient for three lead pans, cach seven feet long by six feet broad and
fifteen inches deep. They should be constructed of twelve pounds lead to the
square foot. The lixiviation will be complete in six or eight hours in a
vessel of the above description, and should then be run off at 36° Twaddell's
hydrometer into a large settling cistern placed in a hot chamber in order
to settle the silica (silex) of the clay and to prevent the crystallization of the
alum. The settling cistern should be constructed of five pounds lead to the
square foot, and of the following dimensions: fifteen feet long, six feet broad,
and two feet and a half deep, and strengthened with a stout wooden frame.
The cistern is best placed in a sloping direction about two feet from the
floor at the lower end and two feet and a half at the higher end. A chamber,
eighty feet long, twenty-six feet broad, and nine feet high, having a small
furnace at one end and a flue running along the centre two feet broad and
covered with cast-iron plates, will be amply sufficient for settling twelve tons
of alum per week. The hot chamber should be supplied with a lead pump
with a small cistern attached for receiving the clear liquor of the large
settling cisterns. After settling, the clear liquor may now be pumped
away to the usual boilers for concentration. Thirdly, for soda alum
and sulphate of soda, take one ton (2240 lbs.) of nitrate of soda, mix
it with two thousand pounds in powder of dry Cornish clay; then take of
the mixture every two hours seventeen pounds for a vitriol chamber, making
a ton and a half (3360 lbs.) per diem of sulphuric acid, specific gravity 1848,
and put it into a nitre pot; pour in and stir twenty pounds of sulphuric acid,
specific gravity 1750; place the nitre pot and its contents, as before, above
the burning sulphur of a pyrites kiln, and at the end of four hours it should
be withdrawn. Of the above product take five hundred pounds, and lixiviate
in one of the lead pans with sixty-seven pounds sulphuric acid, specific
gravity 1400. A strong solution at the end of six or eight hours may be
run off into a settling cistern placed in the open air. The clear liquor may
then be concentrated for soda alum, or it may be decomposed by two
hundred and fifty pounds acid sulphate of potash (sal enixum) into potash
alum and acid sulphate of soda. The latter should be run off into a rever-
beratory furnace for making sulphate of soda, and there converted into
sulphate of soda by the addition of seventy-five pounds of common salt for
every three hundred imperial gallons of the solution of the acid sulphate of
soda and 30° Twaddell's hydrometer. I would remark, that although I
believe that the clay above mentioned to be the best for the purpose, others
may be resorted to, or albite or felspar may be used.
The above particulars and examples are given for the more full explana-

page_text: tion of the said Invention, and the manner in which the same is to be
performed; I do not, however, confine myself to these details; but what I
claim is, the forming a compound of sulphuric acid with the alumina potash
or soda of clays, albite, or felspar, either by the action of heat and sulphuric
acid alone or combined with a salt of potash or soda in vessels contained
within sulphur burners or kilns used in the process of manufacturing
sulphuric acid.
In witness whereof, I, the said William Birkmyre, have hereunto set
my hand and seal, this Seventeenth day of March, in the year of our
Lord One thousand eight hundred and forty-five.
WILLIAM (L.S.) BIRK IKE.
AND BE IT REMEMBERED, that on the Seventeenth day of March, in
the year of our Lord 1845, the aforesaid William Birkmyre came before our
said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Enrolled the Nineteenth day of March, in the year of our Lord One
thousand eight hundred and forty-five.