CERTAIN IMPROVEMENTS IN MANUFACTURING OR MAKING WHITE LEAD
Year: 1826

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PETER
GROVES, of Liverpool Street, in the City of London, Esquire, send greeting.
WHEREAS His present most Excellent Majesty King George the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Fourth day of July, One thousand eight hundred and twenty-
six, in the seventh year of His reign, did, for Himself, His heirs and suc-
cessors, give and grant unto me, the said Peter Groves, His especial licenco
that I, the said Peter Groves, my exors, adñiors, and assigns, or such others
as I, the said Peter Groves, my exors, adiñors, 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
also in all is said Majesty's Colonies and Plantations abroad, my Invention
of "CERTAIN IMPROVEMENTS IN MANUFACTURING OR MAKING WHITE LEAD;" in
which said Letters Patent is contained a proviso, obliging me, the said Peter
Groves, 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 IIis
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.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Peter Groves, do hereby declare that the nature of my said Invention, and tho
manner in which the same is to be performed, are particularly described and
ascertained in the following description thereof (that is to say) :-
My improvement for making white lead, or a white oxide of lead, or
ceruse, consists in making it from sulphuret of lead, commonly called calena
or lead ore, and in a manner different from any other person. I take half
a ton of calena or lead ore and break it very small with hammers or stampers,
and afterwards reduce it to a fine powder in a crushing mill or a mortar ;
I then burn or roast it, taking care not to apply so much heat as to melt
it; when cold, I grind it and wash it in vats or tubs, so as to float off
the fine particles, and grind the coarse ones over again, proceeding thus
till the whole is ground very fine; I then dry it in pans in a kiln or heated
room, or in the open air; when dried, I reduce it again to a powder and mix
it with two hundred pound of nitrate of potash or nitre, commonly called
saltpetre. This mixture is put into a vessel which I call a retort, but which I
do not claim to be new. It may be thus described: it consists of a cylinder or
tub of iron or other metal, the side sand bottom of which are double, with a
space of three inches between, sufficient for steam to circulate freely in. The
cylinder is lined internally with lead; its height altogether measures four feet,
and its diameter three feet six inches. A leaden cistern is placed above, with
two pipes of the same metal leading from it, the one having a stop-cock,
which passes directly through the cylinder into the interior at the upper part,
the other supplies a forcing pump, which has a pipe furnished with a stop-cock
that opens into the bottom of the cylinder to force the acid into the bottom of
the mixture, in order that every part may be equally supplied with acid. (The
stop-cocks are necessary to prevent any of the mixture getting back into the
pipes.) To the cylinder also is attached a high-pressure steam boiler with all
the necessary apparatus, having two pipes for conducting steam, one of which
opens into the cylinder, the other into the space between its sides. All these
parts must be very well and accurately made, and constructed with great care,
and particular attention must be paid to having proper cocks; in fact the wholo
inust be of very superior workmanship. Near to the top in the side of the
retort or cylinder is cemented a large tube, about six inches in diameter, which
passes into a receiver or condenser, or else into the open air, to let off the gas or
vapour generated by the mixture. A top or cover lined with lead is fitted to the
cylinder, and screwed down to a flange on the top of the outer edge of it. In
the middle of the cover is a stuffing box, through which an iron rod or spindle
turned to fit it passes, having arms cased or covered with lead, such as is com-

page_text: monly used for mixing white lead and oil. This rod or spindle may be
turned either by hand or machinery. There is likewise a hole with a stopper
to fit close in the cover of the retort or cylinder, large enough to introduce a
small ladle from time to time for taking out a portion of the matter in the
cylinder, so as to observe the progress of the operation. Having steam pre-
pared, and having put the mixture before described into the retort or cylinder
and screwed down the top or cover, I charge the cistern with two hundred
pounds of sulphuric acid, not concentrated, but of specific gravity from one
thousand four hundred to one thousand seven hundred and forty; I then
introduce part of this acid by means of the pipe leading from the cistern
to the top of the retort or cylinder, and at the same time, by means
of the forcing pump, I force into the bottom of the materials another
portion of the acid, keeping the spindle in motion all the time. When
the materials have been well stirred so as to be thoroughly mixed, I
admit the steam in the space between the outer and inner sides of the
retort or cylinder, continuing to pump in at intervals the acid till the whole is
admitted. This generally occupics from four to five hours, when the steam is
turned off, leaving the matter to remain twenty-four hours at least, but
generally longer, as three or four days, some ores requiring more time to
oxidize than others, stirring it two or three times every day; I then take the
matter out of the retort or cylinder and put it into a cistern lined with lead,
let it settle two or three days, and take off all the acid which rises to the sur-
face, the matter is then dried, reduced to powder, and the operation repeated
with the same quantity of saltpetre and acid as beforo described. It is then
washed in hot water until the acid is completely extracted, which may be
known by the water being colourless and tasteless, or by its not discolouring
substances tinged with vegetable matter; I then grind it in cold water and
wash it in the manner that white lead is ground and washed; it is then dried
and fit for use.
I think it necessary to make the following observations that every part may
be clearly understood; other sort of retorts may be used, provided they are
made so as to allow of the matter being stirred or agitated, and fire may be
used in place of steam. The gas which is disengaged may be either suffered to
pass off into the open air above the building where the process is carried on, or
may be received into a condenser, or burnt, or otherwise disposed of, but care
must be taken not to let any escape from the retort or cylinder into the place
in which you work. When the lead ore is particularly soft and free from other
substances and well burnt the operation will be perfect by a single process. I
sometimes use nitrous acid for the second part of the process, mixing it with

page_text: the matter after the first process in the retort. It is then dried, proceeding in
the manner before described. I sometimes also mix the saltpetre with the ore
previously and burn them together, but this requires a larger quantity of salt-
petre than by the other method. After having burnt it, I put into the retort
and add the sulphuric acid to it; or it may be done by burning it with nitrc,
and also putting it into the retort with a smaller quantity of nitre; these, how-
ever, are only variations of the same plan.. Other acids or compounds of acids
or their bases may be also employed. If the ore is hard and mixed with
other substances, especially iron, after having burnt it, ground it fine, and
dried it, and reduced it to powder, I mix it with sulphuric acid for three or
four days, or longer, before I mix the nitre with it in the retort or cylinder.
In witness whereof, I, the said Peter Groves, have hereunto set my
hand and seal, this Second day of January, in the year of our Lord