IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN ALKALI SALTS
Year: 1847

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
ALBERT TILGHMAN, of Scotts Yard, Bush Lane, London, Chemist, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of
Great Britain and Ireland, bearing date at Westminster, the First day of
February, One thousand eight hundred and forty-seven, in the tenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Richard Albert Tilghman, my exors, admors, and assigns,
Her especial licence, full power, sole privilege and authority, that I, the said
Richard Albert Tilghman, my exors, adñiors, and assigns, or such others as
I, the said Richard Albert Tilghman, 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, and in all Her Majesty's Colonies and Plantations abroad, and
also in the Islands of Jersey, Guernsey, Alderney, Sark, and Man, my Inven-
tion of "IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN ALKALI SALTS;" in
which said Letters Patent is contained a proviso that I, the said Richard
Albert Tilghman, shall cause a particular description of the nature of my
said Invention, and in what manner the same is to be performed, by an
instrument in writing under my hand and seal, to be inrolled in Her

page_text: 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
Richard Albert Tilghman, do hereby declare that the nature of my said
Invention, and the manner in which the same is to be performed, are fully
described and ascertained in and by the following statement thereof, that is
to say:-
My Invention consists in a method of obtaining the sulphate, muriate, and
chromate of potash from the felspars containing that alkali. The felspars
best for the purpose are those containing the largest quantity of potash, and
the proportions of materials directed to be used in the different processes
hereafter described are calculated for a felspar containing sixteen per cent. of
potash. I obtain sulphate of potash by heating together at or above redness
a potash felspar, lime or its carbonate, and the sulphate of either lime, baryta,
or strontia, and afterwards lixiviating the mixture with water. I have tho
materials ground to fine powder, and mix them intimately in the proportion
of two parts by weight of felspar, one part of lime, or an equivalent quantity
of carbonate of lime, and one part of sulphate of lime, which I prefer to
the other sulphates. I place the mixture upon the hearth of a reverberatory
furnace, and heat it to bright redness for about eight hours, turning the
charge from time to time, so that all parts may receive equal heat; although
the formation of sulphate of potash is most rapid at a high temperature, yet I
clo not let the heat rise high enough to cause the fusion or agglutination of the
mass, as the subsequent extraction of the salt by water is thereby rendered
more difficult. The presence of a deoxidizing atmosphere in the furnace
being injurious to the formation of the sulphate of potash, I admit through
suitable openings above the level of the fire a sufficient quantity of air into
the gases rising from the fuel to preserve the atmosphere in an oxidizing
state. When all parts of the charge have remained at a high red heat for
from eight to ten hours, I withdraw the charge from the furnace, and lixiviato
it with hot water repeatedly, as somic of the salt adheres obstinately to the
sulphate of lime.
The solution of sulphate of potash is then evaporated,
the sulphate of lime which deposits during the evaporation being continually
removed. When the sulphate of baryta or strontia is used in place of the
sulphate of lime, the same process is to be pursued, but the extraction of
the sulphate of potash by water is more easy, owing to the less solubility of
the sulphates of baryta and strontia. When a cheap and abundant supply

page_text: of sulphurous acid gas can be obtained, as from the roasting of sulphurous
ores, the use of the sulphate of lime or other sulphate in the mixture may
be dispensed with, by doubling the quantity of lime or of carbonate of lime
before prescribed, and exposing the charge, while at a red heat in the furnace,
to a current of sulphurons acid gas and air with frequent stirring. Sulphate
of lime is thus formed during the process, and the formation of sulphate of
potash takes place as in the former case. I obtain muriate of potash by
heating together a potash felspar, and the muriate of either soda, lime, or
iron at a temperature above the fusing point of the muriate employed. I
prefer using muriate of soda or common salt, which I mix with an equal
weight of finely ground felspar. The mixture is well dried and introduced
into a horizontal iron cylinder, with an opening only at one end, which is
closed with an iron door or cover and luted tight. For the escape of any
gas that might tend to burst the cylinder, I have a small holo through the
upper part of this door, which is closed at pleasure by a loosely fitting plug.
The cylinder is covered on the outside with fire brick, to protect the iron
from the action of the fire. The cylinder and its contents are to be heated to
bright redness for about six hours; the heat should be abo the fusing point
of the muriate employed, but I prefer to keep it below the temperaturo at
which the felspar would melt, as the charge would then be more difficult to
remove from the cylinder. The cover is now taken off, and the charge
raked out as quickly as possible into an iron pot, which is immediately
covered, and kept closed until the mass is cool. The soluble salts are to
be extracted from the mass by water, and the muriate of potash separated
from the other salt by evaporation and crystallization in the usual manner.
The same process is pursued when the muriate of lime or iron is employed.
I obtain chromate of potash by heating to bright redness for several hours
in an oxidizing atmosphere, an intimate mixture of finely ground. potash
felspar, lime, and chrome ore. The materials are ground to fine powder, and
mixed in the proportion of four parts by weight of felspar, four of lime,
or an equivalent quantity of carbonate of lime, and one of chrome ore. I
spread the mixture on the hearth of a reverberatory furnace, and keep it
at a bright red heat for from eighteen to twenty hours, stirring and turning
it over frequently, so that all parts may be equally exposed to heat and
air, as with the sulphato of potash. An oxidizing atmosphere is preserved by
the admission of sufficient air into the chamber of the reverberatory furnace.
The heat should not be permitted to rise high enough to cause even incipient
fusion in the charge, which should be kept in a porous state. When an
examination of the charge in the usual manner shows that it contains the

page_text: proper quantity of alkaline chromate, it is withdrawn from the furnace, and
lixiviated with water, as in the common process.
I claim as my Invention the manufacture of sulphate of potash, by heating.
at or above redness, a mixture of a potash felspar, lime, and the sulphato
of either lime, baryta, or strontia.
I also claim the manufacture of muriate of potash, by heating together a
potash felspar and the muriate of either soda, lime, or iron, at a temperature
above the melting point of the muriate employed.
And I also claim the manufacture of chromate of potash, by heating to
redness a mixture of a potash felspar, lime or its carbonate, and chrome ore,
all in fine powder, in an oxidizing atmosphere.
In witness whereof, I, the said Richard Albert Tilghman, have hereunto
set my hand and seal, this Thirty-first day of July, in the year of our
Lord One thousand eight hundred and forty-seven.
RICHARD A. (L.s.) TILGHMAN.
AND BE IT REMEMBERED, that on the Thirty-first day of July, in the
year of our Lord 1847, the aforesaid Richard Albert Tilghman 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 abovo
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Enrolled the Thirty-first day of July, in the year of our Lord One thousand
eight hundred and forty-seven.