Improvements in the Manufacture of White Lead and Colored Pigments.
Year: 1892

page_text: The decision of the Chief Examiner, acting on behalf of the Comptroller, of the
1st day of September 1894, allowed, under Section 18 of the Patents, &o. Aot,
1883, an Amendment of this Specification.
Date of Application, 17th Nov., 1892
Complete Specification Left, 16th Aug., 1893-Accepted, 23rd Sept:, 1893
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of White Lead and Colored
Pigments.
We, ROWLAND MATTHEWS of 72 Bishopgate Street Within in the City of
London, Gentleman, and JAMES NOAD of High Street, East Ham, in the County
of Essex, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
This invention relates to improvements in the manufacture of what is commonly
known as white lead, and to the manufacture of colored pigments.
According to our invention we take any lead oxide litharge or massicot or a
natural carbonate of lead oxydised and grind same in water until a hydrated lead
float is obtained.
The float se produced we treat with an acetin solution composed of acetic acid,
glycerine and water which is ordinarily prepared as follows:-
For every gallon of water we add about one ounce of acetic acid of a strength
of say 40 degrees, Beaumé and about 1 ounce of glycerine and for every gallon of
the solution so produced we add about 20 ounces of the hydrated lead float, the bath
being agitated at intervals for a period of about forty-eight hours, or until it is
found that the hydrated lead float has become corroded, carbonic acid gas is then
injected and carbonate of lead is thereby produced.
The bath is then run off from the mixer and treated with dilute solution of soda
or other alkali to remove all traces of the acid that may remain after which the
carbonate of lead is dried.
The proportion of carbonate and unconverted oxide of lead in the finished
product may be varied by varying the strength of the solutions and the duration
of their action, and in lieu of introducing the carbonic acid gas after the agitation
period it may be introduced at an earlier part of the process or even introduced
into the acetin solution.
It is indeed of advantage to introduce at intervals small quantities of carbonic
acid gas during the period that the float is being acted on by the acetin, say in all
not to exceed about one cubic foot for every seven pounds of lead suspended in the
solution, but the quantity should be less than what is required to complete the
conversion of the float to carbonate.
When we desire to produce a colored pigment we add to the bath suitable
coloring agents which are not liable to be injuriously acted upon by the substances
present, and proceed as above described, but we do not always find it necessary
to remove the traces of acid as above described, inasmuch as the colouring agents
themselves may be alkaline, and if we wish to increase the brilliancy of the pig-
ments instead of using an acetin solution we may substitute for the acetic acid
any other suitable acid, for example nitric acid of say a strength of 1,420 degrees.

page_text: As an example of this part of our process let it be assumed that we wish to
produce a blue pigment then before adding the bulk of the carbonic acid we add
for each one hundred pounds of float lead in the bath a solution of yellow prussiate
of potash of a strength sufficient to introduce about one per cent. of that substance,
and agitate the bath occasionally for say half an hour after which we add a
solution of ferric chloride or other iron salt in sufficient quantity to introduce
about two and one half per cent. of that substance, the bath being agitated for a
further period of about fifteen minutes after which hydrochloric acid or other
suitable acid is added in sufficient quantity to produce the shade of blue required.
The pigment is then dried.
To produce a canary yellow we add to the bath about three and one half per cent.
of bichromate of potash, or we may use chromic acid, the pigment being then
thrown down if necessary by the use of carbonic acid.
For an orange or deep red, we use the same quantity of bichromate of potash
and then cause the bath to be heated or made to boil until the desired shade is
obtained, the pigment is then dried.
Dated this 17th day of November 1892.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Chartered Patent Agent.
COMPLETE SPECIFICATION (AMENDED).
Improvements in the Manufacture of White Lead and Colored
Pigments..
We, ROWLAND MATTHEWS of 72 Bishopsgate Street Within, in the City of
London, Gentleman, and JAMES NOAD of High Street, East Ham, in the County of
Essex, Electrical Engineer, do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to improvements in the manufacture of what is commonly
known as white lead, and to the manufacture of colored pigments.
According to our invention we take any lead oxide which is capable of being acted
upon by a solution of acetic acid and glycerine such as litharge or massicot or a
natural carbonate of lead heated to form oxide of lead and grind same in water
until a lead float is obtained. The float so produced we treat with a solution
composed of acetic acid and glycerine.
The following proportions we find answer well in practice. We take 20 ounces
of lead float and add to it 1 ounce of glycerine and 1 ounce of acetic acid specific
gravity 1040. The mixture is agitated by any well known mechanical means,
and when it commences to stiffen, water is added in small quantities at a time until
it becomes of a pasty consistency. It is now allowed to stand for from 24 to
48 hours, sufficient water is added so that it can be readily agitated. At this
stage we find it advantageous to float off the light particles leaving any metallic
lead or unconverted oxide to be returned to the mill which grinds the lead float,
the liquor containing the light particles which have been floated off is treated with
sufficient carbonic acid gas to form carbonate of lead, (an excess of gas must be
avoided otherwise normal carbonate of lead will be formed which is deficient in
covering power). The bath is then run off and treated with a dilute solution of
soda or other alkali to remove all traces of the acid that may remain after which
the carbonate of lead is washed, dried and ground ready for use, the liquor we use
over and over again for grinding the float.
.
The proportion of carbonate and unconverted oxide of lead in the finished
product may be varied by varying the strength of the solutions and the duration
of their action, and in lieu of introducing the carbonic-acid gas after the agitation
period it may be introduced at an earlier part of the process or even introduced

page_text: into the solution containing the glycerine, acetic acid and lead float. It is indeed
of advantage to introduce at intervals small quantities of carbonio neid gas during
the period that the float is being acted on, say in all not to exceed about one ou bie
foot to every seven pounds of lead suspended in the solution, but the quantity
should be much less than what is required to complete the conversion into
carbonate.
When we desire to produce a colored pigment we add to the bath suitable
coloring agents which are not liable to be injuriously acted upon by the substances
present and proceed as above described, but we do not always find it necessary
to remove the traces of acid as above described inasmuch as the coloring agents
themselves may be alkaline, and if we wish to increase the brilliancy of the pig-
ments instead of using acetic acid we may substitute for this acid any other suitable
acid for example nitric acid of say a strength 1420 degrees. As an example
of this part of our process let it be assumed that we wish to produce a blue pig-
ment, then before adding the bulk of the carbonic acid we add for each one hundred
pounds of float lead in the bath a solution of yellow prussiate of potash of a strength
sufficient to introduce about one per cent. of that substance and agitate the bath
occasionally for say half an hour, after which we add a solution of ferric chloride
or other iron salt in sufficient quantity to introduce about two and one half per cent.
of that substance, the bath being agitated for a further period of about fifteen
minutes, after which hydrochloric acid or other suitable acid is added in sufficient
quantity to produce the shade of blue required. The pigment is then dried.
To produce a canary yellow we add to the bath about three and one half per cent.
of bichromate of potash, or we may use chromic acid, the pigment being then
thrown down if necessary by the use of carbonic acid.
For an orange or deep red we use the same quantity of bichromate of potash,
and then cause the bath to be heated or made to boil until the desired shade is
obtained. The pigment then is dried.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that
what we claim is :-
1. In the manufacture of white lead and colored pigments the use of a solution
containing glycerine, substantially as set forth.
2. The process of manufacturing white lead which consists in treating the float
lead with a solution containing glycerine and acetic or other suitable acid, and
admitting carbonic acid to the bath and finally neutralizing it with an alkali,
substantially as set forth.
3. The process of manufacturing white lead and colored pigments, substantially
as described.
Dated the 16th day of August 1893.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London,
Chartered Patent Agent for the Applicants.