A MODE OF PREPARING OR MANUPAC- TURING OF A WHITE FROM THE IMPURE NATIVE SULPHATE OF BARFTES
Year: 1825

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
DUESBURY, of Bonsal, in the County of Derby, Color Manufacturer, send
greeting.
WHEREAS His present Majesty King George the Fourth, by His Letters
Patent under the Great Seal of the United Kingdom of Great Britain and
Ireland, bearing date at Westminster, the Twenty-ninth day of September now
last past, did give and grant unto me, the said William Duesbury, His
especial licence, full power, sole privilege and authority, that I, the said
William Duesbury, my executors, administrators, and assigns, and such others
as I, the said William Duesbury, my executors, administrators, or assigns,
should at any time agree with, and no others, from time to time and at all
times thereafter during the term of years therein expressed, should and law-
fully might make, use, exercise, and vend, within England, Wales, and the Town
of Berwick-upon-Tweed, my Invention of "A MODE OF PREPARING OR MANUPAC-
TURING OF A WHITE FROM THE IMPURE NATIVE SULPHATE OF BARFTES;" in which
said Letters Patent there is contained a proviso obliging me, the said William
Duesbury, by an instrument in writing under my hand and seal, particularly
to describe and ascertain the nature of my said Invention, and in what
manner the same is to be performed, and to cause the same to be inrolled in

page_text: His Majesty's High Court of Chancery within six calendar months next and
immediately after the date of the said recited Letters Patent, as in and by the
same, reference being thereunto had, will more fully appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
William Duesbury, do. hereby declare that the nature of my said Invention
and the manner in which the same is to be performed, are particularly
described in and by the following account or description thereof, that is to
say:-
I take the impure native sulphate of barytes, which is also known by the
names of cawk, heavy spar, ponderous earth, terra ponderosa, vitriolata,
-marmor metallicum, &c., which is to be found in this country in large
quantities, and pick and wash it as clean as may be from impurities; I
then grind or reduce it to a state of considerable. division in a pan or colour
mill, or other proper apparatus, with the addition of water. I next transfer
the cawk so ground into a leaden cistern or boiler and add more water to it;
the cistern or boiler is supported upon iron plates having a proper fireplace
and flues underneath them, constructed in brickwork as usual, in order that
the contents of it may be brought to a boiling heat; I then add to the cawk
sulphuric acid in proportion to the quantity of iron supposed to be contained
in it, but which, however, may be ascertained by taking portions of tho cawk cut
from time to time during the boiling, and examining the-same. to. see whether
it has attained the proper degree of whiteness, and if not, more acid must be
added and the boiling continued until the desired colour be produced, the matter
also being stirred during the process to prevent its adhering to the bottom
_ of the boiler. It must then be repeatedly washed with water until the
solution of iron is removed from it. It is lastly dried in a stove or otherwise,
to fit it for use. I can also employ other acids than the sulphuric or com-
pounds of acids with bases, with an intention of dissolving the iron, although
I prefer to use the sulphuric acid in the manner above described. In case of
employing other acids or their compounds which would act on the leaden
boiler, vessels of glass, earthenware properly glazed, or of other materials
not liable to be attacked or corroded by the said acids or their compounds,
must be, used instead of the leaden boiler. I can also employ a copper boiler
instead of-a leaden one, even when I am using the sulphuric acid to dissolve
the iron, although I give the preference to one formed of lead. I do not
mean or intend hereby to claim as my Invention the apparatus herein
described, but solely to limit my claim to the purification of the impure
natave sulphate of barytes; or by what other name it may be called, from its
colouring matters, by the action of acids or their compounds, and rendering

page_text: the same equally fit for those purposes to which white sulphate of barytes is
usually or may be applied in the arts.
In witness whereof, I, the said William Duesbury, have hereunto set
my hand and seal, this Twenty-ninth day of March, in the year of
our Lord One thousand eight hundred and twenty-six.
WILLIAM DUESBURY. (L.S.)
AND BE IT REMEMBERED, that on the same Twenty-ninth day of
March in the year above mentioned, the aforesaid William Duesbury
came before our Lord the King in His Chancery, and acknowledged the
Specification aforesaid, and all and every thing therein contained, in form
above written. And also the Specification was stamped according to the
tenor of the Statute in that case made and provided.