Improvements in the Manufacture of Basic Carbonate of Lead or White Lead.
Year: 1890

page_text: Date of Application, 4th Dec., 1890
Complete Specification Left, 3rd Oct., 1891-Accepted, 7th Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Basic Carbonate of Lead or
White Lead.
We, WATSON SMITH, Lecturer in Chemical Technology, University College,
London, and WILLIAM ELMORE, Electro-metallurgist, 47 Clapham Road London,
do hereby declare the nature of this invention to be as follows:-
In operating the acetate of ammonium process for the production of white lead
or basic carbonate of lead from oxide of lead, litharge or massicot, according to the
Specification of MacIvor and others, No. 10426* of 18 July 1888 amended,
No. 6815 of 23rd April 1889 and of MacIvor and Smith, No. 16,093 of October 10th
1890 respectively, we have discovered that when the impurer forms of oxide of
lead are used, certain metallic impurities may be introduced which are either
detrimental to the white lead formed or to the acetate of ammonium which' is
recovered for use over again.
In our application for Letters Patent No. 19323 of the 27th Nov. 1890, we
have set forth our improved method of dealing with such impurities in the white
lead.
The present invention relates to a mode of dealing with the gradual accumulation
of copper in the acetate of ammonium, containing also it may be, carbonate of
ammonium, and obtained on passing carbonic acid through the magmas or solutions
of basic acetate of lead, obtained by the action of acetate of ammonium on oxide of
lead (litharge or massicot), but not passing it through in excess, nor even so as to
precipitate all the lead in solution or to change all the carbonate of ammonium into
acetate of ammonium but to leave some in solution.
In the presence of this residuum of carbonate of ammonium, conferring alkalinity
on the liquid, copper remains in solution and can be removed from the white lead
by suitably washing and the use of the filter press.
Having found that such gradual accumulation of copper in the recovered acetate
of ammonium liquors takes place and that in cases of the use of inferior qualities
of litharge, such accumulation would soon bring about a block in the cycle of
operations and chemical reactions-(the continuity of which cycle at present confers
continuity on the processes referred to)-if some method were not adopted for
removing the copper from time to time as found expedient, we effect the removal
of such accumulation of copper in the following manner :-
When by suitable tests, it is found desirable that at a particular stage in the
continuous revolutions of the process, the copper shall be removed from the acetate
of ammonium liquors recovered, previous to use over again, care is taken by the
addition of a little ammonia or carbonate of ammonium when the usual volume and
proportion of carbonic acid has been passed in in the carbonating process, that all
the lead, or almost all, is precipitated in the final fraction of lead carbonate thrown
down, and yet the copper shall be retained in solution.
The liquors now obtained by washing the white lead in the filter press or other-
wise and from the last fraction of lead carbonate, and containing the copper, may
be made slightly acid with acetic acid and either treated with zinc or subjected,
preferably, to the action of an electric current from a primary battery, dynamo or
suitable source of electricity, electrodes of carbon being employed in the cupreous
solution. If the solution be not made acid the deposition of the copper will take
place but a longer time is necessary.
By this means the copper is deposited from the solution upon the carbon
cathode.
“To ascertain the points at which copper is either present in too great quantity,

page_text: or is sufficiently removed, a small sample of the solution is made slightly alkaline, if
not already so, with ammonia and then boiled to remove ammonia and two or three
drops of potassium ferrocyanide added, when a reddish brown colouration or precipi-
tate is formed. Standard colorimetric tests may be thus adjusted, suitable for the
use and guidance of the workman or foreman.
Dated this 4th day of December 1890.
WATSON SMITH.
WILLIAM ELMORE.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Basic Carbonate of Lead or
White Lead.
We, WATSON SMITH, Lecturer in Chemical Technology, University College,
London, and WILLIAM ELMORE, Electro-metallurgist, 51 Handford Road, Clapham
Road, London, 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 :-
In operating the acetate of ammonium process for the production of white lead or
basic carbonate of lead from oxide' of lead, litharge or massicot, according to the
Specifications of MacIvor and others No. 10426* of July 1888 amended, No. 6815
of 20 April 1889, and of MacIvor and Smith No. 16093 of October 10th 1890
respectively, we have discovered that when the impurer forms of oxide of lead
(litharge or massicot) are used in the process, that certain metallic impurities
notably copper, may be introduced which are either detrimental to the white lead
produced ultimately or to the acetate of ammonium which is recovered in the cycle
of operations, for use over again.
In our Specification No. 19323 of the 27th Nov. 1890 we have set forth our
improved method of dealing with such impurities, and more particularly copper, so
as to keep it out of the white lead produced.
The present invention relates to a mode of dealing with the gradual accumula-
tion of copper dissolved in the acetate of ammonium solutions, which latter, will be
also more or less ammoniacal as well as contain lead, the result of the previous
incomplete precipitation with carbonic acid as described in No. 19323 of
Nov. 27th 1890. The ammoniacal condition of the acetate of ammonium liquors
is due to the presence both of ammonia and carbonate of ammonia, for we have
found that in such solutions it is quite possible for some lead to exist unprecipitated
along with ammonia and a certain amount of carbonate of ammonium.
The copper in these solutions obtained as described in No. 19323 of 27 Nov. 1890,
can be completely removed from the white lead by suitably washing in the filter
press.
Having found that such gradual accumulation of copper in the recovered
acetate of ammonium liquors takes place and that in cases of the use of inferior
qualities of litharge which contain copper, such accumulation would soon bring
about a block in the cycle of operations (the continuity of which at present confers
continuity on the processes referred to)-if some method were not adopted for
removing the copper from time to time as found necessary, we effect this removal of
copper in the following manner :-
When by suitable tests it is found necessary at a particular stage in the cycle of
operations that the copper shall be removed from the acetate of ammonium liquors
recovered previous to use over again (had they been pure enough) carbonic acid is
passed in, and in the carbonating process care is taken that it shall be passed in in
sufficient excess to precipitate all the lead, or all but minute quantities, when a little
ammonia is added so that most of the copper will remain in and be contained in the
acetate liquors thus obtained.
The acetate liquors thus obtained and containing copper, should be made slightly

page_text: acid with acetic acid and either treated with zinc in some suitably and finely
divided form, the solution being either cold or warm, or digested either cold or
preferably warm with a slight excess of finely divided or precipitated metallic lead,
the solution being made distinctly acid with acetic acid; or, the cupreous acetate
liquors subjected preferably to the action of an electric current from a primary
battery, dynamo or suitable source of electricity, electrodes of carbon or other
suitable material being employed in the cupreous solution.
If the solution be not made acid the deposition of the copper will take place, but
a longer time is necessary.
By this means the copper is deposited from the solution upon the carbon or other
suitable cathode.
To ascertain the points at which copper is either present in too great quantity, or
is sufficiently removed, a small sample of the solution is made slightly alkaline, if
not already so, with ammonia, and then boiled to remove the ammonia in excess.
Then two or three drops of potassium ferrocyanide are added; when the appearance
or non-appearance of a reddish brown precipitate or colouration will demonstrate
the presence or absence of copper. Standard colorimetric tests may thus be
adjusted, suitable for the use and guidance of the workman or foreman.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
Firstly. In the acetate of ammonium process for the production of white lead
according to the Specifications of MacIvor and others, No. 10426* amended, of
18 July 1888; No. 6815 of 20th April 1889, and of MacIvor and Smith No. 16093
of Oct. 10th 1890; the removal of copper when desirable from the acetate of
aminonium liquors recovered after the precipitation of white lead in the above pro-
cesses as described, by electrolytic deposition either in a faintly alkaline, neutral, or
slightly acid solution, preferably the last, and the use of carbon or other and
suitable electrodes
Secondly. The use for the above purpose of precipitation, of metallic zinc or
lead in some suitably and finely divided form, the solution being either cold or warm
(and having been made acid with acetic acid), for the purpose of removing copper
from the acetate of ammonium liquors, recovered after the precipitation of white
lead in the above processes specified.
Dated this 20th day of Santambar 1891
WATSON SMITH.
WILLIAM ELMORE.