IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD
Year: 1836

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HEMMING, of Edward Street, Portman Square, in the County of Middlesex,
Gentleman, send greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Thirteenth day of October, in the seventh year of His
reign, did, for Himself, His heirs and successors, give and grant unto me,
the said John Hemming, His especial licence, full power, sole privilege and
authority, that I, the said John Hemming, my exors, admors, and assigns,
or such others as I, the said John Hemmings, 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 "IMPROVEMENTS IN THE MANUFACTURE
OF WHITE LEAD;" in which said Letters Patent is contained a proviso that
I, the said John Hemming, shall cause a particular description of the nature
of my said Invention, and in what manner the same is to be performed, to
to be inrolled in His 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
John Hemmings, do hereby declare that the nature of my said Invention,
and the manner in which the same is to be performed, are particularly

page_text: described and ascertained in and by the following statement thereof, that is
to say:-
I take nitrate of soda or nitrate of potash, the former I prefer, as being a
cheaper article and equally adapted for the purpose required, and having
separated the impurities add to it a sufficient quantity of sulphuric acid to
separate the nitric acid by distillation. The residue, which is sulphate of
soda, I convert into carbonate of soda, by mixing with a sufficient quantity
of coal, lime, or chalk, and heating intensely in a reverberatory furnace.
I then take oxide of lead prepared by heating metallic lead with free access of
air, or manufactured by any other process, or the litharge or massicot formed
in separating silver from lead, and dissolve it in the nitric acid distilled from
the nitrate of soda or potash, as before described, the nitric acid being
previously diluted with about six times its volume of water. I then add a
clear solution of the carbonate of soda or potash, made with fair water, to the
clear solution of lead dissolved in the dilute nitric acid, until all the lead
is precipitated as carbonate of lead or white lead. When the white lead has
duly subsided, I draw off the supernatant liquor, and wash the precipitate with
fair water, which is in like manner to be drawn off when the precipitate has
again subsided and added to the former liquor. I boil or evaporate these
liquors to dryness, and the result is nitrate of soda or potash. This is again
heated with sulphuric acid to separate the nitric acid, and the residual salt of
soda or potash is again to be converted into a carbonate by the process before
described. These processes to be repeated, so that the nitrate of soda or
potash employed shall be recovered, and again converted into carbonates.
I claim to use in the mode described pyroligneous or acetic acid, or any
other acid capable of dissolving the oxide of lead, and also any other alkaline
or earthy carbonate, but I prefer the nitric acid as prepared from nitrate of soda.
I do not claim for any novelty in the manufacture of the acid employed, nor
for the conversion of the sulphate of soda or potash into carbonate of soda or
potash, nor for the precipitation of lead from its solution by an alkaline
carbonate. But I claim for the combination and application of the processes
herein described to the manufacture of white lead, and to the continued
recovery of the nitrate of soda or potash employed, and of the carbonate of
potash or soda.
In witness whereof, I, the said John Hemming, have hereunto set my
hand and seal, this Thirteenth day of April, in the year of our Lord
One thousand eight hundred and thirty-seven.
JOHN (1.8.) HEMMING.

page_text: AND BE IT REMEMBERED, that on the Thirteenth day of April,
in the year of our Lord 1837, the aforesaid John Manning came before our
said Lord the King in His 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.