IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD
Year: 1869

page_text: LETTERS PATENT to William Robert Lake, of the "International
Patent Office," No. 8, Southampton Buildings, London, Consulting
Engineer, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF WHITE LEAD." -A communication from abroad by George
Thompson Lewis, of Philadelphia, Pennsylvania, United States of
America.
Sealed the 9th October 1869, and dated the 12th July 1869.
PROVISIONAL SPECIFICATION left by the said William Robert Lake
at the Office of the Commissioners of Patents, with his Petition,
on the 12th July 1869.
I, WILLIAM ROBERT LAKE, of the "International Patent Office,'
No. 8, Southampton Buildings, London, Consulting Engineer, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE MANU-
FACTURE OF WHITE LEAD," a communication, to be as follows:-
Heretofore dry white lead or the basis of white lead pigment has been
made from metallic lead. When galena or sulphuret.of lead has been
used it has been first reduced to metallic lead. The process of making
dry white lead or the basis of white lead pigment from metallic lead
most generally practised is by the use of acetic acid in earthen vessels

page_text: immersed in decomposing matter, such as dung or tan. The production
of white lead by this treatment requires from five to twelve weeks, and
it then has to be ground, washed, and dried before it is fit to be used
as the basis of a pigment.
In manufacturing white lead according to this Invention the ordinary
galena or sulphuret of lead is treated in an ore crusher, and then
desulphurized in an ordinary desulphurizing kiln or oven. It is then
mixed with carbon, preferably in the state of fine washed pea or dust
anthracite coal in the proportion of half and half, and then heated in the
reducing furnace known as the "Wetherill zinc furnace;" dense white
fumes or vapors pass off, which can be collected in the form of a
powder in bags or screens. Lead in this condition will form when
mixed with oil a superior white pigment. It differs from and is superior
in quality as a pigment to the white oxide of zinc or metallic lead or
anything heretofore produced from mixed metallic ores.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Robert Lake in the Great Seal Patent
Office on the 11th January 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ROBERT LAKE, of the "International Patent Office," No. 8, Southampton
Buildings, London, Consulting Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of July, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Robert Lake, Her special
licence that I, the said William Robert Lake, my executors, adminis-
trators, and assigns, or such others as I, the said William Robert
Lake, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after 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 Inven-
tion for "IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD," upon
the condition (amongst others) that I, the said William Robert Lake,

page_text: 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 William Robert Lake, 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:-
Heretofore dry white lead or the basis of white lead pigment has been
made from metallic lead by the use of acid. When galena (native
sulphuret of lead) has been, used it has been first reduced to metallic
lead. The process most generally pursued in making dry white lead
or the basis of white lead pigment from metallic lead is by the use of
acetic acid in earthen vessels immersed in decomposing matter, such as
dung or tau. This treatment requires from five to twelve weeks. The
lead is then ground, washed, and dried before it is fit to be used as the
basis of a pigment.
In manufacturing white lead according to this Invention the ordinary.
galena (native sulphuret of lead) is treated in an ore crusher. It is then
roasted in an ordinary desulphurizing kiln or oven, and then mixed with.
earbon, preferably in the state of fine washed pea or dust anthracite.
coal in the proportion of half and half. I then heat the mixture in a
compound reducing and oxydizing furnace, and dense white fumes or
vapors pass off. These are conveyed into a separate chamber or recep-
tacle, where the vapors are strained by passing through bags or screens.
of muslin or other fabric, or are allowed to deposit by being passed
slowly through an extended chamber in the way in which lampblack,
oxide of zinc, etc. have been heretofore collected. To prevent the fluxing
of the mass together, and otherwise to facilitate the subsequent operations,
caustic lime or the carbonate of lime (in the form of pulverized limestone
or otherwise) may be added to the mixture of carbon and roasted ore in
the proportion of about two hundred pounds of lime to every four hundred
pounds of the galena; this addition is not essential, although under some
circumstances it is desirable and beneficial. Lead in this condition will
form when mixed with oil a superior white pigment. It differs from
and is superior in quality as a pigment to the white oxide of zinc or

page_text: anything heretofore produced from mixed metallic ores. The product
obtained by this improved process may be used not only as the basis of
pigment, but as a drier and in all manufactures where pure white oxide
of lead is desired. The furnace which I have found to work well for
the purposes above mentioned is commonly known as the "Wetherill "
zinc furnace, and is represented in the annexed Drawings, in which
Figure 1 is a plan of the said furnace; Figure 2, a front elevation; and
Figure 3, a back elevation thereof; Figure 4 is a vertical section on the
line x, x, Figure 1.
a is the main chamber, the bottom b. of which is composed of iron bars
perforated with small holes about one-quarter of an inch apart, and
preferably made slightly conical, with the larger diameter downward.
The size of the holes would be such as to prevent the crushed ore and
coal from falling through; these perforated bars are suitably sustained
at the ends on the front and back walls. The ash-pit below the per-
forated bottom is of equal area therewith, and is provided with a door e
in front, and with a hole fat the back for the reception of a pipe from
suitable blowing apparatus. The walls g, g, and arch or top h should
be built of some refractory substance, such as fire-brick.. The front is
entirely open, and provided with sliding doors i, by which it can be
closed when working the process or open to remove the residuum. At
the back there are two sliding jams j, j, to give access to the main
chamber for stirring the charge and for inspection. At the back near
the arch there is a hole governed by a sliding damper leading to a
chimney for carrying off smoke and impure gases in the beginning of
the operation on a new charge. In the centre of the roof there is an
aperture governed by a damper or sliding door m leading to a suitable
apparatus for the collection of the oxydized vapors of lead. The exterior
walls n, o, p, q, may be built above the top to form two feeding
troughs, r, one on each side of the arch or roof, and provided each
with an aperture or passage & leading to the inside or main chamber, and
each aperture or passage is provided with a cover to be put on after the
furnace has been charged.
Having thus described the said Invention as communicated to me by
my foreign correspondent, I claim,-
First. The manufacture of the basis of a pigment by treating galena
(native sulphuret of lead) by roasting, and afterwards mixing the roasted
mass with carbon, and subjecting it to the action of heat in a compound

page_text: reducing and oxydizing furnace, and collecting the fumes, as above
described.
Second. Roasting galena (native sulphuret of lead). and then sub-
liming the same and oxydizing the vapors and collecting them as formed
in a separate chamber for the purpose of forming a basis of pigment, and
for other purposes, substantially as set forth.
Third. A white oxide of lead produced by roasting the galena, then
subliming and oxydizing the same, and collecting it in a separate
chamber.
In witness, whereof; I, the said William Robert Lake, have here-
unto set my hand and seal, this Eleventh day of January, in
the year of our Lord One thousand eight hundred and seventy.
WILLIAM ROBERT LAKE. (L.S.)
Witness,
H. J. GEDGE,
Clerk to Messrs. Haseltine, Lake, & Co.,
8, Southampton Buildings,
London.