IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD
Year: 1866

page_text: LETTERS PATENT to William Robert Lake, of the "International Patent
Office, No. 8, Southampton Buildings, Chancery Lane, in the County
of Middlesex, Consulting Engineer, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF WHITE LEAD."-A communication from abroad
by William Bell, Thomas Mara Fell, and Ambrose George Fell, all of
the City, County, and State of New York, United States of America.
Sealed the 7th May 1867, and dated the 28th November 1866.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at
the Office of the Commissioners of Patents, with his Petition, on the
28th November 1866.
I, WILLIAM ROBERT LAKE, of the "International Patent Office," No. 8,.
Southampton Buildings, Chancery Lane, in the County of Middlesex, Con-
sulting Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD," & communication, to be
as follows:-
The nature of the said improvements consists, first, in the production of
the sulphate of lead from the ores of lead, also from metallic lead and from
the oxide of this metal by a novel and expeditious method; second, in the

page_text: treatment of the sulphate so produced in order to obtain a superior white
lead; third, in the production of a new precipitate of lead by using sulphuric
acid with muriatic acid to form a double precipitant; fourth, in the novel
treatment of this substance by alkalies to improve its quality.
In the production of the sulphate from the ores of lead the said ores must
be as free as possible from silica, iron, copper, or other foreign matters. The
said ores are well ground, then submitted to a thorough oxydation by the
usual process of roasting, which is best performed in a reverberatory furnace.
This preliminary preparation converts the common sulphide or the carbonate
under treatment into oxide. When preparing oxide from metallic lead it is
preferable to adopt the ordinary method of making litharge, the object being
to produce a complete oxide.. In the conversion of the resulting oxides of
lead (whether the same are produced from ores or metallic lead) into sulphate
the said oxides are first ground to a fine powder, which powder is intimately
mixed in a suitable vessel with about two and a half per centum of nitric
acid and sufficient water to form a thin pasty mass. This per-centage of
nitric acid is about the best proportion, although almost any quantity from
one to fifty per cent. may be used. It will be seen in the next stage of the
process that the nitric acid merely acts in the capacity of an agent or
auxiliary, which is almost immediately liberated, nearly the entire quantity
thereof being finally recovered for further use in its original condition.
Sulphuric acid is then introduced with more or less water sufficient to keep
the mass in a thin paste. This combination when attacking the nitrates
(produced by the nitric acid) generates heat, and a quantity of sulphate of
lead is instantly formed. The nitric acid set free again attacks a fresh
portion of oxide, converting it also into a nitrate of lead, which is no sooner
formed than it is again separated by the stronger sulphuric acid, and a
further supply of sulphate is produced. This action and reaction is continued
until the whole mass is converted, which generally takes place in the course
of a few hours. Instead of using nitric acid acetic acid may be substituted.
The nitric acid is recovered by allowing the sulphate to settle down on the
bottom of the vessel, when the said acid can be drawn off for further use. It
may also be recovered after the formation of the sulphate by gentle evaporation
in pans or other vessels, and then condensed. After being thus obtained the
sulphate of lead is submitted to an intimate contact with a heated solution of
potash or other alkali in boilers or other vessels, being at the same time well
stirred. The proportion of the alkali to the sulphate is about three per
centum, and the time required for this operation about two or three hours.
The effect of this alkali (which may be either potash or soda or both) is to
D

page_text: deprive the sulphate of a portion of the sulphuric acid held in combination
with it, and thereby produce a new article which possesses qualities superior
to the best white lead of commerce hitherto known; this is then washed in
vats and collected and dried at a low temperature by heating in pans or on
shelves in a building expressly constructed for air drying. The proportion of
the. ingredients employed may be varied, and very similar results may be
obtained by the use of other alkalies or the salts of these materials. The
constitution of the sulphate may also be first changed into carbonate of lead
by the use of either carbonate of potash, soda, or lime, and finally treated
with the alkaline solution. An alkaline effect on this sulphate is also
produced by the direct use of the carbonate of soda or potash without the
after treatment by the alkaline solution, and gives about the same results.
The great objection to precipitated salts of lead as hitherto produced has been
the crystaline structure of the particles, which crystaline structure is owing
to a large per-centage of acid and water absorbed and held in the composition
of the said salts. This non-opacity destroys the property known as body, and
prevents the after formation of an oleate of lead. In the production of these
salts according to this Invention a precipitate is obtained highly opaque and
free from crystals, and its production is effected with a great saving in the
amount of alkali used. A solution or salt of lead being obtained by any of
the well-known methods in use for that purpose a precipitant (termed by me
a hydrosulphuric) is prepared by intimately mixing about ten parts of muriatic
(or hydrochloric) acid of 18° with ninety parts of sulphuric acid; of 60° and
with more or less water. This prepared precipitant is then gradually combined
with the solution of lead in tanks lined with closely-rolled sheet lead, glass, or
rubber, or into other vessels capable of resisting the action of acids. The
precipitate thus obtained is next well washed with water, then pressed nearly
dry by an bydraulic press, and treated with about one per centum of either
potash or soda alkali in another vessel, where it is boiled or warmed from three
to four hours with the alkali. The precipitate is then allowed to cool off and
settle down, and is washed to receive any free alkali; it may then be dried in
pans in warm chambers and is ready for use. After the precipitation of the
lead by the hydrosulphuric the nitric acid or other solvent employed is freed
and ready for further use.

page_text: 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 27th May 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ROBERT LAKE, of the "International Patent Office," No. 8, Southampton
Buildings, Chancery Lane, in the County of Middlesex, Consulting Engineer,
send greeting.
:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of November, in the year of our
Lord One thousand eight hundred and sixty-six, in the thirtieth 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, administrators, 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 thereafter.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
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF WHITE LEAD," upon the
condition (amongst others) that I, the said William Robert Lake, 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 (that is to say) :-.
The nature of the said improvements consists, first, in the production of
the sulphate of lead from the oxide of lead by a novel and expeditious method;
second, in the treatment of the sulphate so produced in order to obtain a
superior white lead; third, in the production of a new precipitate of lead by
using sulphuric acid with muriatic acid to form a double precipitant;
fourth, in the treatment of this substance by alkalies to improve its quality.
The sulphate is obtained by placing in a vessel constructed with a stirrer or
other suitable contrivance for the purpose and containing oxide of lead, about

page_text: two and a half per centum of nitric acid, and sufficient water to form a thin
pasty mass, and gradually add without change of vessel to this mixture
sulphuric acid, with more or less water to keep such mixture still in a thin
pasty condition. The addition of the sulphuric acid causes considerable heat
when attacking the nitrates produced by the nitric acid, and quickly forms a
portion of sulphate of lead, liberating the nitric acid; the nitric acid thus
set free again attacks a fresh portion of oxide, converting it also into a nitrate
of lead, which is no sooner formed than it is again separated by the stronger
sulphuric acid, and a further supply of sulphate is produced.. This action and
reaction is continued until the whole mass is converted, which conversion
generally takes place in the course of a few hours. The oxide is not first
formed into a complete solution by the nitric acid, but only a very small per-
centage is placed with the oxide, when the sulphuric acid is gradually intro-
duced, and the change into a nitrate of lead first and then into a sulphate of
lead next takes place by portions, that is to say, all is not first changed into a
complete solution of nitrate of lead and then such nitrate precipitated into a
sulphate, or in other words, by a separate and continuous process with respect
to each. By this manipulation all is effected in one vessel of smaller compass,
and the quantity of nitric acid used is economized, while the product is less
crystalline than that derived by other methods. It is evident that any per-
centage of nitric acid may be used less than what will make a complete
solution of nitrate of lead, but the per-centage above mentioned is very
effective and quite economical. The nitric acid may be nearly all recovered
after the formation of the sulphate by subjecting the mass to the action of an
hydraulic press; it may also be recovered by gentle evaporation by means of
heat in pans or other vessels and then condensed.
;-
1
The way to derive the product, which is termed a basic chloro-sulphate of
lead, is as follows:-A precipitant is first prepared by intimately mixing about
ten parts of muriatic (hydrochloric) acid of eighteen degrees Baumè with
ninety parts of sulphuric acid of sixty degrees Baume, adding more or less
water. This prepared precipitant is then gradually introduced into a solution
of lead derived by placing oxide in nitric acid or acetic acid, or other solvents
of lead contained in vessels capable of resisting the action of acids, such as
tanks lined with closely-rolled sheet lead, glass, or rubber, and the whole is
well agitated by any suitable means adapted for continual stirring. Sulphuric
acid when used separately produces a very crystalline white lead, such is also
the case with respect to muriatic acid. The latter acid when used alone
imparts to the lead an impure color, while the combination of these two acids
gives a brilliant and opaque white lead free from crystals, and much whiter

page_text: ་
than is obtained by the use of either acid alone. This precipitate or product
requires only a very short process to render it superior to the white lead now
in use in respect to body, color, and the property of forming an oleate with
oil. The proportions of the materials above given, though found to be the
best in practise, may be varied without materially affecting the results.
Now the sulphate of lead derived as first above described is converted into
'merchantable. white lead as follows:-The precipitated sulphate is of inferior
value on account of its crystalline structure and want of what is termed body
For spreading quality. These defects are entirely removed by the mode of
treatment berein described and a fine close-grained white lead is the result.
To reach this end, and obtain a product which is superior to the best white
-lead of commerce, we submit this sulphate to an intimate contact with an
-alkali solution contained in boilers or other vessels and boil it from two to
three hours, the proportion of the alkali to the sulphate being about three
per centum. The effect of the alkali is to deprive the sulphate of a portion
of its acid and water in combination therewith and thereby produce a new
article with qualities as above stated. This product is next well washed with
water and subjected to the action of an bydraulic press for the purpose of
solidifying the mass to facilitate handling, and afterwards dried on pans in
warm chambers or in any other convenient manner. The above proportion of
talkali is the most advantageous, but may be somewhat varied. An alkaline
effect will also be produced on the sulphate by the use of any one of the
alkaline compounds.
i. When treating the basic chloro-sulphate of lead so as to obtain a very fine
and pure, white lead, the process last mentioned is followed, except that
only a very small per-centage of alkali need be used with this sulphate,
thereby causing a great saving in alkali. This precipitate without the alkali
treatment is quite opaque or free from crystals, is much finer grained, and
whiter than any heretofore obtained, and may be used for the ordinary
purposes to which white lead is applied, but with such subsequent treatment
a very superior article is produced.
i Having thus fully described the said improvements, as communicated to me
by my foreign correspondents, and shewn how the same may be conveniently
and advantageously carried into practise, I claim,-.
First, the production of a sulphate of lead, substantially in the manner
and for the purpose described.
Second, the treatment of the sulphate of lead with an alkali solution, or
with an alkaline compound, substantially in the manner and for the purpose
described.

page_text: Third, the production of a precipitate, substantially in the manner and for
the purpose described.
Fourth, the treatment of the precipitate with an alkali solution or with
an alkaline compound, substantially in the manner and for the purpose
described.
In witness whereof, I, the said William Robert Lake, have hereunto
set my hand and seal, this Twenty-fifth day of May, in the year of our
Lord One thousand eight hundred and sixty-seven.
0 Witness,
GEORGE HASELTINE,
Civil Engineer,
WILLIAM ROBERT LAKE. (L.S.)
8, Southampton Buildings,
London.