IMPROVEMENTS IN THE MANUFACTURE OF WHITE-LEAD
Year: 1881

page_text: LETTERS PATENT to Henry John Bollmann Condy, of Battersea, in the
County of Surrey, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE
OF WHITE-LEAD."
PROVISIONAL SPECIFICATION left by the said Henry John Bollmann
Condy at the Office of the Commissioners of Patents on the 14th March
1881.
HENRY JOHN BOLLMANN CONDY, of Battersea, in the County of Surrey.
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD."
The object of this Invention is the production of white lead used in the manu-
facture of paint by a process hereinafter described, which will not only expedite its
production, but will make a white lead of excellent body, free or nearly so from
the usual impurities clinging to white lead of ordinary manufacture.
The old and well known Dutch process of producing white lead by corrosion
through the medium of acetic acid, and transformation into a substance known as
white lead through the agency of carbonic acid generated by fermenting tan, has
many objections; such lead is impregnated with foreign metals and impurities,
which to a certain extent affect the color, wheras the white lead produced according
to my improved process hereinafter described possesses (in addition to the
advantage of saving time in its production) increased purity of color, and is also
free or nearly so from foreign metals and other impurities.
These objects I am able to accomplish by producing a lead, hereinafter described,
precipitated from a solution of basic or acetate of lead, previously freed completely
or nearly so from all impurities contained in lead or oxide of lead, whereas it is
well known ordinary commercial white lead produced by corrosion of metallic lead
must contain a large percentage of the impurities existing in that substance.
I am well aware many attempts have been made and numerous Patents taken
out to manufacture white lead by precipitation; many of these Inventions have
been for the production of white lead by means of basic acetate of lead, from which
it has been thrown down by carbonic acid, but white lead so produced is deficient
in body, generally varying in composition from and on this account inferior to
that made by the Dutch process herein referred to; whereas according to my
improved process I produce precipitated white lead having all the body and good
qualities of corroded white lead, and identical in composition, and this I accomplish
by precipitating a soluion of pure or nearly pure tri basic acetate of lead by means
of bi carbonate of soda.
.The composition of white lead should be two equivalents of carbonate of lead,
Laathon with one cauivalent oxida 2 Pho
"

page_text: As my Invention is designed for producing a white lead agreeing with this
formula I will now proceed to describe the same as follows:-
I take of crystallized acetate of lead 189 parts, and mix therewith 224 parts of
best litharge or any other form of protoxide of lead, or a proportionate quantity of
any inferior oxide of lead, which may be necessary to furnish the 224 parts
of oxide. To this I add 21 lbs. of water and grind the whole mass together.
I then let it stand, say, for about 24 hours, during which period the whole or
nearly so of the oxide of lead combines with the acetate of lead, and forms tri-
basic acetate, which when dissolved in water excludes nearly all foreign matters
and impurities contained in the original oxide.
I then dissolve this compound in a quantity of water, by preference 10 times its
weight, and allow it to settle till bright, when I decant from the sediment the
supernatant liquor into another vessel, and add to the latter bi-carbonate of soda
in the proportion of about 84 lbs. to the 189 lbs. of crystallized acetate of lead
originally employed.
At this stage the mixture should be tested in order to ascertain that the lead
salt and soda salt have been employed in proper proportions to precipitate nearly
the whole of the lead. I prefer to employ a slight excess of the tri-basic lead salt
rather than find carbonate of soda in excess. The bi-carbonate of soda should be
added in the dry state as it occurs in commerce.
This mixture of tri basic acetate of lead and bi-carbonate of soda gives rise to
the formation of a precipitate of white lead, 3 Pbo 2 Co 2, and acetate of soda in
solution, the latter of which is to be separated from the former by filtration and
compression. The filtrate consists of a solution of acetate of soda, which can be
evaporated by the usual means and crystallized. The solid matter in the press
consists of white lead and a certain percentage of water, the latter of which must
be driven off by drying in an ordinary white lead stove or drying room. If the
precaution has been taken to ensure a slight excess of soluble acetate of lead (as
recommended) in the liquor, which is separated by pressure from the white lead,
it should previously to being evaporated be treated with a small quantity of
carbonate or bi-carbonate of soda, added by degrees and determined by testing so
as to precipitate all the remaining oxide of lead in the form of carbonate or oxy
carbonate, which should be allowed to settle or separated by filtration before
beginning to evaporate the solution referred to, and the small quantity of pre-
cipitate thus formed after being pressed and dried can be added to the bulk of
white lead previously described.
The exact process may be varied by the employment in lieu of crystallized sugar
of lead of a solution of the same boiled down, and then mixed with oxide of lead;
or the solution of sugar of lead may be boiled with oxide in conformity with
instructions found in chemical books.
Another method by which it might be produced is to heat or mix acetic acid
with 3 equivalents of oxide of lead; but whether made from oxide of lead and
acetic acid, or oxide of lead and acetate lead, or finally if made by means of acetic
acid or acetate of lead in solution poured on and drawn off alternately at intervals of
time over metallic lead or granulated lead, so as to saturate it with sufficient lead
after it has become oxidised by means of atmospheric air, the object should be to
make tri-basic acetate of lead, and I prefer to make this by the method I have
already previously explained.
By following exactly the instructions I have given I find I obtain a nearly
perfect white lead, almost free from all the usual impurities, and of excellent

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry John Bollmann Condy in the Great Seal Patent Office on the
14th September 1881.
HENRY JOHN BOLLMANN CONDY, of Battersea, in the County of Surrey.
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD."
The object of this Invention is the production of white lead used in the
manufacture of paint by a process hereinafter described, which will not only
expedite its production but will make a white lead of excellent body, free or
nearly so from the usual impurities contained in white lead of ordinary
manufacture.
The old and well known Dutch process of producing white lead by corrosion
through the medium of acetic acid and transformation into a substance known as
white-lead through the agency of carbonic acid generated by fermenting tan has
many objections; such lead is impregnated with foreign metals and impurities,
which to a certain extent affect the color, whereas the white-lead produced
according to my improved process, hereinafter described, possesses (in addition to
the advantage of saving time in its production) increased purity of color and is
also free or nearly so from foreign metals and other impurities.
These objects I am able to accomplish by producing a lead, hereinafter described,
precipitated from basic acetate of lead, dissolved or suspended in water, and
previously freed completely or nearly so from all impurities contained in lead or
oxide of lead, whereas it is well known ordinary commercial white lead produced
by corrosion of metallic lead must contain a large percentage of the impurities
existing in that substance.
I am well aware many attempts have been made and numerous Patents taken
out to manufacture white-lead by precipitation; many of these Inventions have
been for the production of white-lead by means of basic acetate of lead, from
which it has been thrown down by carbonic acid, but white-lead so produced is
deficient in body, generally varying in composition from and on this account
inferior to that made by the Dutch process herein referred to, whereas according
to my improved process I produce precipitated white-lead having all the body and
good qualities of corroded white-lead, and identical in composition, and this I
accomplish by precipitating pure or nearly pure tri-basic acetate of lead either
dissolved or suspended in water by means of bi-carbonate of soda.
The composition of white-lead should be two equivalents of carbonate of lead,
together with one equivalent oxide, 3 Pbo 2 Co 2.
As my Invention is designed for producing a white-lead agreeing with this
formula I will now proceed to describe the same.
For the purpose of making tri-basic acetate of lead I employ one or other of the
following plans; that which I profer is first described :-
Firstly. I find it practicable to produce basic acetate of lead with two equivalents
of lead from granulated metallic-lead, on which dilute acetic-acid is poured and
drawn off alternately at intervals of time. For this purpose I use acetic acid of
specific gravity 1045 in the proportion of two gallons of acid to ten gallons of
water. This solution will in the course of two or three days attain the specific
gravity of about 1.200, and when the proper amount of lead is found by testing
to have been dissolved it can be evaporated to dryness and then ground with oxide
of lead in the proportion of 112 lbs. of oxide of lead to 275 lbs. of dry bi-basic
acetate of lead, adding thereto about 50 lbs. of water.
Secondly. I take of crystallized acetate of lead 189 parts and mix therewith
224 parts of best litharge, or any other form of protoxide of lead, or a
proportionate quantity of any inferior oxide of lead which may be necessary to
furnish the 224 parts of oxide; to these add 21 lbs. of water and grind the whole
mass together. ·

page_text: I allow the mixture of bi-basic acetate of lead and oxide of lead employed as
described in the first method, or of neutral acetate of lead and oxide of lead as
described in the second method, to stand, say, for about 48 hours, during which
period the whole or nearly so of the oxide of lead combines with the acetate of
lead and forms tri-basic acetate, which, when dissolved in water, excludes
nearly all foreign matters and impurities contained in the original oxide.
I then dissolve this compound in a quantity of water, by preference ten times
its weight, and allow it to settle till bright, when I decant from the sediment the
supernatant liquor into another vessel and add to the latter bi-carbonate of soda
in the proportion of about 84 lbs. to every 112 lbs. of oxide of lead contained in
the tri-basic acetate of lead which has been employed as described. At this stage
the mixture should be tested in order to ascertain that the lead salt and soda salt
have been employed in proper proportions to precipitate nearly the whole of the
lead;
prefer to employ a slight excess of the tri-basic lead salt rather than find
carbonate of soda in excess. The bi-carbonate of soda should be added in the dry
state as it occurs in commerce.
This method may be varied by employing the tri-basic acetate of lead partly
dissolved and partly suspended in water, that is, not absolutely as a bright
solution.
This mixture of tri-basic acetate of lead and bi-carbonate of soda gives rise to
the formation of a precipitate of white lead, 3 Pbo 2 Co 2, and acetate of soda in
solution, the latter of which is to be separated from the former by filtration and
compression. The filtrate consists of a solution of acetate of soda, which can be
evaporated by the usual means and crystallized. The solid matter in the press
consists of white lead containing a certain percentage of water, the latter of
which must be driven off by drying in an ordinary white lead stove or drying
room.
If the precaution has been taken to ensure a slight excess of soluble acetate of
lead (as recommended) in the liquor which is separated by pressure from the white
lead it should previously to being evaporated be treated with a small quantity of
carbonate or bi-carbonate of soda added by degrees and determined by testing, so
as to precipitate all the remaining oxide of lead in the form of carbonate or
oxycarbonate, which should be allowed to settle or be separated by filtration before
beginning to evaporate the solution referred to, and the small quantity of
precipitate thus formed, after being pressed and dried, can be added to the bulk of
white lead made as previously described.
By following exactly the instructions I have given I find I obtain a nearly
perfect white lead, almost free from all the usual impurities, and of excellent
body.
Having now described the nature of my said Invention, together with the means
I employ for carrying the same into practical effect, I wish it to be understood in
conclusion, that what I claim as new and as of my Invention is,―
First. The production of tri-basic acetate of lead by the new and simple plan
herein substantially described; and,
Second. The manufacture of white lead from tri-basic acetate of lead precipitated
by means of bi-carbonate of soda in the manner as herein substantially described.
In witness whereof, I, the said Henry John Bollmann Condy, have hereunto
set my hand and seal, this the Fourteenth day of June, in the year of
our Lord One thousand eight hundred and eighty one.