IMPROVEMENTS IN THE MANUFACTURE OF ALKALIES AND ALKALINE EARTHS
Year: 1855

page_text: LETTERS PATENT to Richard Albert Tilghman, of the City of Philadelphia,
United States of America, Chemist, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF ALKALIES AND ALKALINE EARTHS"
Sealed the 15th January 1856, and dated the 3rd August 1855.
PROVISIONAL SPECIFICATION left by the said Richard Albert Tilghman
at the Office of the Commissioners of Patents, with his Petition, on the
3rd August 1855.
I, RICHARD ALBERT TILGHMAN, of the City of Philadelphia, United States
of America, Chemist, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF ALKALIES AND ALKALINE EARTHS" to be
as follows:
My improvement consists in decomposing the sulphates of the alkaline
earths by exposing them at a high heat alternately to the action of deoxidizing
and oxidizing agents, whereby the sulphuric acid is gradually driven off and
the alkaline bases are left in a free state.
By exposing sulphate of baryta, for example, at a high heat to a current of
deoxidizing gas, I find that part of its sulphur is carried off in a gaseous state,
while part remains in combination as sulphuret of barium. By now admitting
fresh air to oxidize this sulphuret, part of its sulphur again comes off in a
gaseous state, while a part oxidizes, reproducing sulphate of baryta. By repeat-
ing the alternations of deoxidation and oxidation a sufficient number of times,
the whole of the sulphur may be driven off. I prefer always to finish the
operation by a prolonged oxidation, so as to destroy any sulphuret which might

page_text: otherwise contaminate the product. When either the sulphate used, its sul-
phuret, or its base, are fusible at the heat employed, I prefer to mix it with
magnesia, or other suitable infusible material, so as to preserve the mass in a
porous state. The gaseous compounds of sulphur given off by this operation
may be employed if desired to make sulphuric acid or sulphates by known
processes. I manufacture the alkalies, potash, and soda by digesting the
baryta or strontia produced by the above process with a solution of sulphate of
potash or of soda.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Richard Albert Tilghman in the Great Seal Patent Office on
the 2nd February 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
ALBERT TILGHMAN,- of the City of Philadelphia, United States of America,
Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of August, in the year of our Lord One
thousand eight hundred and fifty-five, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the
said Richard Albert Tilghman, Her special licence that I, the said Richard
Albert Tilghman, my executors, administrators, and assigns, or such others
as I, the said Richard Albert Tilghman, my executors, administrators, and
assigns, should at any time agree with, and no others, from time to time and
at all 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 ALKALIES AND ALKALINE EARTHS," upon
the condition (amongst others) that 1, the said Richard Albert Tilghman, 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
performed, 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 Richard Albert Tilghman, do hereby
declare the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement thereof (that is to say) :-

page_text: My improvement consists in decomposing the sulphates of the alkaline earths
by exposing them at a high heat alternately to the action of deoxydizing and
oxydizing agents, whereby the sulphuric acid is gradually driven off and the
alkaline bases are left in a free state. By exposing sulphate of baryta,
for example, at a high heat to a current of deoxydizing gas, I find that part of
its sulphur is carried off in a gaseous state, while part remains in combination
as sulphuret of barium. By now admitting fresh air to oxidize this sulphuret,
part of its sulphur again comes off in a gaseous state, while a part oxydizes,
reproducing sulphate of baryta. By repeating the alternations of deoxidation
and oxidation a sufficient number of times, the whole of the sulphur may be
driven off. I prefer always to finish the operation by a prolonged oxidation,
so as to destroy any sulphuret which might otherwise contaminate the product.
When either the sulphate used, its sulphuret, or its base, are fusible at the
heat employed, I prefer to mix it with magnesia, or other suitable infusible
material, so as to preserve the mass in a porous state. The gaseous compounds
of sulphur given off by this operation may be employed if desired to make
sulphuric acid or sulphates by known processes.
I manufacture the alkalies,
potash, and soda by digesting the baryta or strontia produced by the above
process with a solution of sulphate of potash or of soda.
Having thus stated the nature of my said Invention, I now proceed to
describe the best means with which I am acquainted for carrying out the
same.
To decompose the sulphate of either baryta or strontia, I first grind it to
I
fine powder, and mix it with half its weight or less of magnesian lime.
prefer that which has had part of its lime removed by washing or acids; a
smaller proportion of it will suffice than of the unwashed. The mixture is
moistened with water, moulded into bricks, and burnt in a kiln, such as is used
in burning fire bricks. When the bricks have reached a bright red or yellow
heat, the decomposing process is commenced by throwing fresh fuel, on all the
fires, and, if needful, partially closing the dampers, so as to render the atmo-
sphere in the kiln strongly deoxidizing. A great quantity of sulphur then
escapes as sulphurous acid, sometimes as sulphuretted hydrogen, and perhaps
in other forms. This evolution of sulphur gradually becomes less strong, and
when it has almost ceased the atmosphere of the kiln is made oxidizing by the
admission of fresh air through suitable openings above the level of the fuel,
and by opening the dampers another discharge of sulphurous acid as copious,
if not more so than the first, now takes place, and on its gradual decline a
deoxidation is again effected as at first. By this repeated alternation of deoxi-
dation and oxidation the whole of the sulphate is decomposed.. The sulphurous

page_text: smell of the escaping gases is a sufficient guide to the workman as to the
proper time. for changing the nature of the atmosphere in the kiln, and when
such a smell is no longer produced by the alternations, it is a sign that the
charge is sufficiently decomposed and ready for the prolonged finishing oxida
tion. When this is ended all the remaining fuel should at once be removed
from the fire places, as, if left to die out gradually during the cooling of the
kiln, a portion of the caustic baryta or strontia .becomes carbonated by it.
Care should be taken to avoid as much as possible allowing the silicious ashes
of the fuel to be carried over by the draught among the bricks. The use of a
fan blast to the fires will be found very convenient (though not at all necessary),
in effecting the desired changes of atmosphere in the kiln; when used, the
fuel can be kept very deep upon the bars, so that carbonic, oxide can be
employed as the chief agent in the deoxidation. The above process can
be carried on in reverberatory furnaces if preferred, in which case little or no
magnesia would be required in the charge, but I consider the above process
more advantageous.
:
When the sulphate of lime is to be decomposed, it does not need the addition
of magnesia to render it porous and infusible in the fire, as its reduction
takes place at a lower heat than that required for the sulphates of baryta or
stroutia. The sulphate of magnesia should first be carefully dried from all
its water of crystallization, and placed in a fire-clay retort, like those used for
gas, and then very gradually heated to redness, having a current of deoxidizing
gas passing through it from the commencement of the heating. The same
alternation of deoxidation and oxidation as before is to be used, but the
decomposition is much more easily effected. I prefer to keep the heat low in
this operation, especially at the beginning, so as to avoid all chance of fusing
the sulphate of magnesia; the caustic magnesia then produced is soft and
impalpable, but if a strong heat is used it becomes harsh and gritty.
In witness whereof, I, the said Richard Albert Tilghman, have hereunto
set hand and seal, this Second day of February, in the year of
my
our Lord One thousand eight hundred and fifty-six.
Witness,
GEO. PITT,
4, Old Square.
R. A. TILGHMAN. (L.S.)