Improvements in the Production of White Lead or Carbonate of Lead.
Year: 1889

page_text: Date of Application, 23rd Aor., 1889
.Complete Specification Left, 21st Jan., 1890-Accepted, 22nd Feb., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Production of White Lead or Carbonate of
Lead.
We, RALPH WALDO EMERSON MACIVOR F.I.C. F.C.S. M. Phy. Society London,
F.R.G.S. &c. &c. of St. Georges Club Hanover Square Analytical and Consulting
Chemist, FREDERICK ARTHUR DARLINGTON C.E. of 13 Eastbank Road Stamford
Hill both in the County of Middlesex, GAVIN PAUL of Haymarket in the City of
Edinburgh and JOHN ALLAN of 12 Woollaston Road Harringay in the County of
Middlesex aforesaid do hereby declare the nature of this Invention to be as
follows:-
"In the Specification of our former Letters Patent dated July 18th 1888
Number 10,426 we described improvements in the production of White lead or
carbonate of lead and apparatus therefor. We have since the said date discovered
further improvements based on those contained in our former Specification which we
will now proceed to describe.
Our present Invention relates to improvements in the production of white lead or
carbonate of lead by the treatment of oxide of lead, that is to say litharge or
massicot with a solution of acetate of ammonia whereby the oxide of lead is
transformed into hydrate of lead, which is subsequently converted into carbonate of
lead by the injection of carbonic acid. The hydrate of lead readily unites with
carbonic acid to yield the final product namely carbonate of lead.
The rapidity with which the convertion of oxide of lead into hydrate can be
effected, depends upon the strength of the acetate of ammonia solution employed that
is to say the weaker the solution the slower will be the conversion. We have found
that for commercial purposes the solution of acetate of ammonia may be used with
advantage of a strength which need not be more than twenty five per cent. or less
than five per cent., a strength of twenty five per cent. operates in a comparatively
short space of time but a strength as low as half a per cent. will effect the hydration
if there be a sufficient quantity of the weak solution, the lead oxide being in a fine
state of division, and time of no object. This half per cent. strength however or any
strength below five per cent. is not recommended for commercial purposes having
regard to the time required for completing the operation. The conversion of the
oxide of lead into the hydrate of lead is effected in the cold (heat may be used but
for commercial operation it is not recommended) the conversion is facilitated by
employing a mechanical arrangement, similar in many respects to that annexed to
our former Specification but modified by connecting the digesting vat with 'a cistern
or vat containing acetic acid whereby any free ammonia carried over during the
operation may be absorbed. And also by introducing carbonic acid to the mass of
hydroxide of lead, formed by the oxide of lead and acetate of ammonia, either by a
series of concentric rings perforated with small holes in the bottom of the vat itself
or by passing carbonic acid down a hollow shaft to which are attached stirrers and
through perforated tubes attached to the blades of the stirrers or by any other means
that may ensure the thorough saturation of the hydroxide of lead so as to form
carbonate of lead.
•
The solution of acetate of ammonia may as stated in our former Specification be
recovered from the white lead and thereafter may be repeatedly used for the
conversion of further quantities of oxide of lead into hydrate of lead which hydrate
is converted into carbonate of lead by the injection of carbonic acid. Theoretically a
given weight of acetate of ammonia in solution should be capable of converting an
unlimited quantity of oxide of lead into hydrate but during the manufacture of white
lead by this process it may be reckoned that there will be a loss of ammonia acetate

page_text: varying with the strength of the solution employed but it should not exceed ten (10)
per cent. on each charge-This loss arises in the washing of the final product and
through the escape of some ammonia during the process.
COMPLETE SPECIFICATION.
Improvements in the Production of White Lead or Carbonate of
Lead.
We, RALPH WALDO EMERSON MACIVOR, F.I.C., F.C.S., M. Phy. Society London,
F.R.G.S., &c. &c., of St. George's Club, Hanover Square, Analytical and Consulting
Chemist, FREDERICK ARTHUR DARLINGTON, C.E., of 13 Eastbank Road, Stamford
Hill, both in the County of Middlesex, GAVIN PAUL, of Haymarket, in the City of
Edinburgh, and JOHN ALLAN, of 12 Woollaston Road, Harringay, in the County of
Middlesex aforesaid, 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 the Specification of our former Letters Patent dated July 18th 1888
Number 10,426 we described improvements in the production of white lead or
carbonate of lead and apparatus therefor. We have since the said date discovered
further improvements based on those contained in our former Specification which we
will now proceed to describe.
Our present invention relates to improvements in the production of white lead or
carbonate of lead by the treatment of oxide of lead, that is to say, litharge or
massicot with a solution of acetate of ammonia whereby the oxide of lead is
transformed into hydrate and acetate which are subsequently converted into carbonate
of lead by the injection of carbonic acid. The hydrate and acetate of lead in
presence of free ammonia formed in the re-action are quickly decomposed by the
carbonic acid yielding the final product namely carbonate of lead and reforming the
acetate of ammonia.
The rapidity with which the convertion of oxide of lead into hydrate can be
effected depends upon the strength of the acetate of ammonia solution employed
that is to say the weaker the solution the slower will be the conversion. We have
found that for commercial purposes the solution of acetate of ammonia may be used
with advantage of a strength which need not be more than twenty five per cent. or
less than five per cent., a strength of twenty five per cent. operates in a comparatively
short space of time but a strength as low as half a per cent. will effect the hydration
if there be a sufficient quantity of the weak solution the lead oxide being in a fine
state of division and time of no object. This half per cent. strength however or any
strength below five per cent. is not recommended for commercial purposes having
regard to the time required for completing the operation. The conversion of the
oxide of lead into the hydrate and acetate of lead is effected in the cold (heat.
may be used but for commercial operation it is not recommended) the conversion is
facilitated by employing a mechanical arrangement similar in many respects to that
annexed to our former Specification but modified by connecting the digesting vat
with a cistern or vat containing acetic acid whereby any free ammonia carried
over during the operation may be absorbed. And also by introducing carbonic
acid to the mass of hydroxide and acetate of lead formed by the oxide of lead and
acetate of ammonia, either by a series of concentric rings perforated with small
holes in the bottom of the vat itself or by passing carbonic acid down a hollow shaft
to which are attached stirrers and through perforated tubes attached to the blades
of the stirrers or by any other means that may ensure the thorough saturation of
the hydroxide and acetate of lead so as to form carbonate of lead.

page_text: The solution of acetate of ammonia may as stated in our former Specification be
recovered from the white lead and thereafter may be repeatedly used for the conversion
of further quantities of oxide of lead into hydrate and acetate of lead which hydrate
and acetate are converted into carbonate of lead by the injection of carbonic acid.
Theoretically a given weight of acetate of ammonia in solution used in conjunction
with carbonic acid should be capable of converting an unlimited quantity of oxide of
lead into carbonate of lead but during the manufacture of white lead by this process
it may be reckoned that there will be a loss of ammonia acetate varying with the
strength of the solution employed but it should not exceed ten (10) per cent. on each
charge. This loss arises in the washing of the final product and through the escape
of some ammonia during the process.
In order that our said invention may be fully understood and readily carried into
effect we will proceed to describe the process more in detail by the aid of the drawings
hereunto annexed.
DESCRIPTION of the DrawINGS.
Figure 1 is a vertical section of the apparatus which we employ and Figure 2 is a
plan of the same.
A is a vat which may be made of wood or other material capable of resisting the
chemicals employed, it may conveniently be six feet in diameter and four feet deep, it
is provided with a closely fitting cover. B is a cistern situate at a higher level and
intended to contain a solution of acetate of ammonia. O is a pipe by which the
solution can be drawn down from the cistern into the vat A, a cock is provided upon
this pipe as the drawing indicates. There is a man hole D in the cover of the vat and
the vat contains an agitator E, with a vertical shaft which can be turned by gearing
as shewn or the agitator may be driven by any suitable motor. The shaft of the
agitator is hollow and pipes ff which stand immediately behind the stirring tines
are connected with the hollow shaft to deliver the carbonic acid gas into the vat or
this may be effected by means of concentric rings laid at the bottom of the vat and
pierced with small holes. The pipes ff are open at their lower ends. G is a cock by
which the liquor can be drawn off from the vat into the receiver I. A pump J is
provided upon the cover of the receiver by which the liquor may be returned into the
vat A. K are outlets by which the white lead is discharged from the vat into the
washing cisterns L and M. N is a man hole which may be opened to facilitate
the emptying of the vat. O is a plug which is removed to let the white lead run out.
of the vat. P is an ammonia catch box it is charged with acetic acid. All the metal
work of the apparatus with which the acetate solution comes into contact should be of
such a character as to resist corrosion or be coated with any material capable of
withstanding attack by the chemicals employed in or formed during the process.
The operation is by preference conducted in the following manner, but the details
admit of variation. The charge of mon-oxide of lead for an apparatus of the dimensions
indicated may weigh about 1120 lbs.
The mon-oxide should be in fine powder and may be either moist or dry. Having
received this charge which is introduced by the upper man hole the vat is closed and
solution of acetate of ammonia is let down upon the charge from the cistern B or pumped
out of the receiver I. The vat A should be charged with the solution of acetate of
ammonia in the proportion of three parts of said solution to one part of lead mon-oxide
by weight. It is convenient to employ a solution containing five per cent. of acetate of
ammonia and the quantities above stated are suited to a solution of this strength, but
the strength of the acetate solution may be varied within wide limits as hereinafter
explained.
The charge of mon-oxide of lead and acetate of ammonia in the vat should be kept
constantly stirred by the agitator until it becomes whitish in color when it will be
found that the mon-oxide of lead has become converted into hydrate and acetate. The
workman will know that this change is complete when the reddish or yellowish
appearance of the mon-oxide of lead disappears and the mass in the vat becomes
whitish in color.

page_text: The hollow axis of the agitator is connected with a pipe by which carbonic acid gas
is supplied to it under pressure sufficient to cause the gas to pass through the contents
of the vat. This gas escapes at the lower ends of the pipes and ascends through the
liquid in which the hydrate and acetate of lead is held suspended. A free flow of this
gas should be maintained and some excess allowed to pass away by a pipe on the cover
into the ammonia catch box P. The pipe dips down into the acetic acid which this
box contains and any ammonia passing off with the carbonic acid gas is caught by the
acid and forms acetate of ammonia. When the hydrate and acetate of lead are
completely converted into basic carbonate and this the workman will know by its
changed appearance, the motion of the agitator is caused to cease, and the white lead
allowed to settle.
There is a gauge glass on the side of the vat A, and in this glass the changes of
appearance can be recognized by which the workman regulates the process.
When the white lead is deposited the liquor is drawn off into the receiver I by
opening the cock G. The plug O is then displaced and the white lead allowed to
descend into the washing cistern L. Below the cock G there is another cock or cocks
in order that any further quantity of liquor may be drawn off in the cistern I if
required. The taper plug O is then raised by being pushed up from underneath the
vat A, through pipe K.
The white lead requires to be well washed with clean cold water.
When a fresh charge of mon-oxide of lead has been placed in the vat A the liquor is
pumped up on to it from the receiver I and then a further quantity of solution is
drawn from the cistern B and also from the ammonia catch box until the proper
quantity has been supplied which is determined by the gauge.
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 :-
1. The improvements in the production of white lead or carbonate of lead, consisting
in the treatment of oxide of lead, that is to say-litbarge or massicot with a solution of
acetate of ammonia in a closed vessel, the contents being agitated by a mechanical
stirrer whilst carbonic acid gas is admitted by pipes arranged substantially as herein
described.
2. The improvements in the production of white lead or carbonate of lead, consisting
in the treatment of oxide of lead, that is to say-litharge or massicot by agitation with
a solution of acetate of ammonia in a closed vessel connected with a cistern charged
with acetic acid; carbonic acid gas being also supplied to the vessel substantially as
herein described.
3. The process substantially as described for the production of white lead or
carbonate of lead from oxide of lead that is to say-litharge or massicot by treating the
same in a closed vessel with a solution of acetate of ammonia of suitable strength as
set forth, and with carbonic acid gas whilst thoroughly agitated.
Dated this 14th day of Januo 1800
R. W. EMERSON MAOIVOR.
FRED. DARLINGTON.
GAVIN PAUL.
JOHN ALLAN.
R. W. EMERSON MACIVOR.
FRED. DARLINGTON.
GAVIN PAUL.
JOHN ALLAN.