A METHOD OF PREPARING AND RESTORING THE CALX OF LEAD AFTER BEING USED IN EXTRACTING THE MINERAL ALKALI FROM COMMON SALT BACK INTO PIG LEAD, BY AN EASIER AND LESS EXPENSIVE PROCESS THAN ANY HITHERTO KNOWN, BY WHICH MEANS A VERY GREAT QUANTITY OF MINERAL ALKALI MAY BE EXTRACTED IN THIS COUNTRY TO ADVANTAGE FROM COMMON SALT
Year: 1788

page_text: BERNIE, of the City of Glasgow, Refiner of Lead, send greeting.
WHEREAS His most Excellent Majesty King George the Third, by His
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twelfth day of August, in the twenty-eighth year of His
reign, upon the petition of me, the said Samuel Birnie, did give and grant
unto me, the said Samuel Birnie, my executors, administrators, and assigns,
His Majesty's especial licence, full power, sole priviledge and authority, that
I, the said Samuel Birnie, my executors, administrators, and assigns, and
every of them, by myself or themselves, or by my or their deputy or deputies,
servants or agents, or such others as I, the said Samuel Birnie, my exe
cutors, administrators, or assigns, should agree with, and no others, from
time to time and at all times thereafter during the term of years therein
expressed, and should and lawfully might make, use, exercise, and vend,
within that part of His Majesty's Kingdom of Great Britain called England,
His Dominion of Wales, and Town of Berwick-upon-Tweed, my Invention
of "A METHOD OF PREPARING AND RESTORING THE CALX OF LEAD AFTER BEING
USED IN EXTRACTING THE MINERAL ALKALI FROM COMMON SALT BACK INTO PIG LEAD,
BY AN EASIER AND LESS EXPENSIVE PROCESS THAN ANY HITHERTO KNOWN, BY WHICH
MEANS A VERY GREAT QUANTITY OF MINERAL ALKALI MAY BE EXTRACTED IN THIS
COUNTRY TO ADVANTAGE FROM COMMON SALT," and that in such manner as to me,
the said Samuel Birnie, my executors, administrators, and assigns, or any of
them, should in their discretion seem meet, and that I, the said Samuel Birnie,

page_text: my executors, administrators, and assigns, should and lawfully might have and
enjoy the whole profit, benefit, commodity, and advantage from time to time
coming, growing, and arising by reason of the said Invention; to have, hold,
exercise, and enjoy the said licence, powers, priviledges, and advantages therein-
before granted or mentioned to be granted unto me, the said Samuel Birnie,
my executors, administrators, and assigns, for and during and unto the full end
and term of fourteen years from the date of the said Letters Patent next and
immediately ensuing, and fully to be compleated and ended, according to the
Statute in such case made and provided; in which said recited Letters Patent
there is contained a proviso, obliging me, the said Samuel Birnie, by an in-
strument in writing under my hand and seal, to cause a particular description
of the nature of my said Invention, and in what manner the same is to be per-
formed, to be enrolled in His Majesty's High Court of Chancery within one
calendar month next and immediately after the date of the said recited Letters
Patent, as by the same [relation being thereunto had] may more fully and
at large appear.
NOW KNOW YE, that a compliance with the said proviso, I, the said
Samuel Birnie, do hereby declare that the method I have invented for pre-
paring a calx of lead for extracting the mineral alkali from common salt, or
other purposes, consists in extracting the silver from the lead by the following
process,
'viz:-
The lead is put into a calcining furnace and calcined with a moderate heat
till it is all or most of it converted into a calx; the calx is then to be melted
without addition, either in the same or in another furnace; when the calx
becomes fluid, the silver, and what lead may be still in a metallic state, will
sink to the bottom, and be thus seperated from the calx. By repeating in
this manner the calcination and melting, all the lead will thus be converted
into a calx, and the silver obtained at last pure; or the silver may be purified
from the last portion of lead by the common process of cuppellation or
refining; or, in place of again calcining by itself the metal got by the first
melting of the calx, it may be calcined with a quantity of fresh lead, and the
calx melted as formerly, and this process may be repeated at pleasure. The
silver being purified at last, as above directed, or the calx prepared, as above,
'may first be used in extracting the alkali from common salt, and afterwards
melted to extract the silver. And the method I have invented of restoring or
reducing back again into lead the above calx, litharge, minium, or any other
calx of lead which has been used in extracting the mineral alkali from common
salt, or which has by any method whatever been combined with the marine,
and consists in adding to the above calx a substance or substances which have

page_text: a strong attraction for the marine acid, by which means the acid is prevented
from volatilizing and carrying off with it in the process of reduction a con-
siderable portion of the metal, which it always does when the calx is reduced
according to the common method, without any other addition than an
inflammable substance. This is done in the following manner, viz*:-To sixteen
parts by weight of the above calx, add one part of lime, or a greater or a less
proportion; they may be mixed either before or after they are put into the
reducing furnace. The reduction is then to be performed in the usual and
common method in practice, by adding to the above mixture pit coal, charcoal,
or any other convenient inflammable substance; or in place of lime chalk may
be used common limestone, the shels of fish, or any calcareous absorbent, or
other substance capable of seperating, with the assistance of heat and an
inflammable substance, the marine acid from the calx of lead. The lime or
other calcareous or absorbent substances used in the reduction will form, with
the marine acid, a marine salt with earthly bases, which may be obtained
from the slag which remains after the reduction by adding water to it,
decanting or drawing off the clear liquor, and then evaporating it to dryness.
In witness whereof, I, the said Samuel Birnie, have hereunto set my
band and seal, the Twenty-eighth day of August, in the year of our
Lord One thousand seven hundred and eighty-eight.
Inrolled the Twenty-eighth day of August, in the year last above
mentioned.