Improvements in the Preparation of Acetate of Ammonia for use in the Manufacture of White Lead by the Acetate of Ammonia Process.
Year: 1891

page_text: Date of Application, 29th Oct., 1891
Complete Specification Left, 28th July, 1892-4ccepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Preparation of Acetate of Ammonia for use in
the Manufacture of White Lead by the Acetate of Ammonia
Process.
WATSON SMITH, Lecturer in Chemical Technology, University College,
London, do hereby declare the nature of this invention to be as follows:-
The object of the present invention is as follows :-
:-
In the operation of the acetate of ammonia process for the manufacture of white
lead or basic carbonate of lead from oxide of lead (litharge or massicot) as
described and detailed in the Specification of R. W. E. MacIvor and Watson
Smith No. 16093 of Oct. 10th 1890, or from galena or sulphide of lead ore, or
suitable residual products or substances containing sulphide of lead, as described
and detailed in the Specification of Watson Smith and William Elmore No. 5501
of March 28th 1891, the use of the material, acetate of ammonia solution all ready
prepared and to hand in proper condition of purity and strength, is pre-supposed.
It would be hence presumed that either the acetate of ammonia solution will be
purchased as such ready for use, or for use after suitable dilution with water, or
that the sufficiently pure materials ammonia solution e.g. liquor ammonia of
commerce, and acetic acid, will be purchased and the mixture of these made at
suitable strengths, and in suitable vessels, and the resulting acetate of ammonia
solution used in the process.
There are certain disadvantages of no small degree, attending either of the
foregoing courses described in outline. In both cases the substances used as
the purchased materials are liquids, volatile and corrosive. They are thus liable to
corrode the vessels in which they are packed and carried, and so themselves contract
impurity, or if packed in glass, glass carboys for example, they form a fragile com-
modity to carry and involve costly freightage, whilst in addition, the working
losses in manufacture and refining by the manipulation and distillation of such
volatile substances, enforce the charge of comparatively high prices. In short, the
forms of liquid ammonia and liquid acetic acid, are the most expensive to adopt,
and the object of the present invention is to present and to claim in connection
with the processes referred to, viz., that contained and specified in No. 16093 of 1890
by R. W. E. MacIvor and Watson Smith, and that contained and specified in
No. 5501 of 1891, by Watson Smith and William Elmore, a cheaper and yet an
equally effective method of preparing acetate of ammonia solution of sufficient
purity on the spot, in the white lead factory, from solid and non-corrosive materials
obtainable in the market.
The materials proposed to be employed are, on the one hand that of crude
acetate of lime known as the grey acetate of lime of commerce, usually obtained
by neutralising the crude wood acetic acids. of the wood distiller, with lime,
evaporating in suitable pans, and "fishing" out with perforated shovels or by other
similar and suitable apparatus from time to time, or continuously, the salted out
acetate of lime from the hot or boiling liquors, or any cheap and sufficiently pure
acetate of lime, and commercial sulphate of ammonia of sufficient degree of purity,
with also sulphate of soda in the form of Glauber's salts or salt cake (calcined
normal sulphate of soda) sufficiently free from iron.
The process is then a composite one, and is carried out as follows :-
:-
(1) The grey acetate of lime is dissolved in as small a quantity of water as
possible and allowed to stand or settle, the scum being then skimmed off. The
clear liquor is run or siphoned off from the insoluble tarry and other heavy
impurities and mixed with an equivalent weight of sulphate of soda also in strong
solution. and suitably settled or filtered, and the mixture is heated.

page_text: Sulphate of lime is precipitated and in falling, carries down with it a considerable
proportion of the remaining tarry and pyroligneous matters in the solution of the
acetate of lime. The solution is filtered off in the filter-press and washed with a
little hot water to remove acetate of soda retained by the sulphate of lime in the
press.
The solution of acetate of soda, probably of a brownish colour, containing
probably also a little sulphate of soda,. is concentrated by evaporation, and when
sufficiently concentrated, is set to crystallise. This it readily does, and if even a
little Glauber's salt crystallized out along with the acetate of soda no harm would
result in the next operation.
(2) The crystals are collected, and drained in a centrifugal machine or in suitable
manner (the mother-liquor being further concentrated for a final crop); they are then
heated in a suitable still of cast iron or other suitable metal or material, with
sulphuric acid of about 140 degrees of Twaddel's hydrometer, in slight excess over
that necessary to form a normal sulphate of soda. Thus any residual adherent
colouring matter retained by the crystals, is destroyed and charred, acetic acid of
considerable concentration and purity distilling over, the distillation being carried
on at as low a temperature as possible.
The fact is, as was discovered after several trials, that on the precipitation or
salting out from a hot solution of the crude acetate of lime, a considerable amount
of tarry and pyroligneous matter becomes included in the but slightly crystalline
masses of acetate of lime separating from the hot liquid. Such tarry and pyro-
ligneous matters are largely eliminated on the contrary, when the well defined
crystals of sodium acetate separate in the improved method.
Thus, a purer acetic acid results from the distillation of the latter salt with
sulphuric acid than will result by the distillation of a correspondingly formed
acetate of lime by the salting out, or "fishing" process, already referred to.
(3.) The acetic acid obtained by exhaustively distilling the acetate of soda as
described, with sulphuric acid, is next neutrallized with lime and carefully
evaporated, when the acetate of lime now salted out and left as a residue will be
found to be nearly quite white and nearly pure, and quite free from the odour of
pyroligneous acid and creosotic matters.
(4.) The acetate of lime is now dissolved in water to form a strong solution and
to this is added the calculated equivalent weight of by preference white sulphate of
ammonia also in concentrated solution, and the mixed solution is heated to from
about 60° C. to 80° C. By the double decomposition ensuing, sulphate of lime is
formed and precipitated, whilst acetate of ammonia remains in solution.
It has been found that what little tarry or pyroligneous and colouring matters
do remain in the acetate of soda, will now be precipitated along with the sulphate
of lime, and thus a clear, colourless and almost pure solution of acetate of ammonia
will be formed, and can be at once, after proper dilution to the required strength,
used for the treatment of the litharge in the white lead process referred to in
Patents No. 16093 of 1890 and No. 5501 of 1891; or for any other purpose to
which acetate of ammonia of such a degree of purity may be applied.
(5.) The crystalline residue of sulphate of soda and carbonaceous residue, left after
treating the acetate of soda with sulphuric acid and distilling as described, is
treated with a small quantity of water, the carbonaceous matter let settle or filtered
off, and the solution is evaporated and crystallized, the Glauber's salt being then
used over again in the process for treating the grey acetate of lime in the first
stage of this process, whilst the sulphate of lime or gypsum, obtained by the double {
decomposition in the final stage, by the action of the purified acetate of lime on
sulphate of ammonia, may be calcined and converted into plaster of paris,
cements, etc., and so no loss be incurred.
Dated this 29th day of October 1901

page_text: COMPLETE SPECIFICATION.
Improvements in the Preparation of Acetate of Ammonia for use in
the Manufacture of White Lead by the Acetate of Ammonia
Process.
I, WATSON SMITH, of University College, London, Lecturer in Chemical
Technology, 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 :-
The object of the present invention is as follows:-
In the operation of the acetate of ammonia process for the manufacture of white
lead or basic carbonate of lead from oxide of lead (litharge or massicot) as
described and detailed in the Specification of R. W. E. MacIvor and Watson
Smith, No. 16093 of Oct. 10th 1890; or from galena or sulphide of lead ore, or
suitable residual products or substances containing sulphide of lead, as described
and detailed in the Specification of Watson Smith and William Elmore, No. 5501
of March 28th 1891; the use of the material, acetate of ammonia solution all ready
prepared and to hand in proper condition of purity and strength is pre-supposed.
It would be hence presumed that either the acetate of ammonia solution will be
purchased as such ready for use, or for use after suitable dilution with water, or
that the sufficiently pure materials ammonia solutions e.g. liquor ammonice of
commerce, and acetic acid, will be purchased and the mixture of these made at
suitable strengths, and in suitable vessels, and the resulting acetate of ammonia
solution used in the process.
There are certain disadvantages of no small degree, attending either of the
foregoing courses described in outline. In both cases the substances used as
the purchased materials, are liquids, volatile and corrosive. They are thus liable
to corrode the vessels in which they are packed and carried, and so themselves
contract impurity, or if packed in glass, glass carboys for example, they form a
fragile commodity to carry and involve costly freightage, whilst in addition, the
working losses in manufacture and refining by the manipulation and distillation of
such volatile substances, enforce the charge of comparatively high prices. In
short, the forms of liquid ammonia and liquid acetic acid, are the most expensive to
adopt, and the object of the present invention is to present and to claim in
connection with the processes referred to, viz., that contained and specified in
No. 16093 of 1890, by R. W. E. MacIvor and Watson Smith, and that contained
and specified in No. 5501 of 1891 by Watson Smith and William Elmore ;-a
cheaper and yet an equally effective method of preparing acetate of ammonia
solution of sufficient purity on the spot, in the white lead factory, from solid and
non-corrosive materials obtainable in the market.
The materials proposed to he employed are, on the one hand that form of crude
acetate of lime known as the grey acetate of lime of commerce, usually obtained by
neutralising the crude wood acetic acids of the wood distiller, with lime,
evaporating in suitable pans, and "fishing" out with perforated shovels or by other
similar and suitable apparatus from time to time, or continuously, the salted out
acetate of lime from the hot or boiling liquors ;-or any cheap and sufficiently pure
acetate of lime, and commercial sulphate of ammonia of sufficient degree of purity,
with also sulphate of soda in the form of Glauber's salts or salt cake (calcined
normal sulphate of soda) sufficiently free from iron.
The process is then a composite one, and is carried out as follows:-
(1) The grey acetate of lime is dissolved in as small a quantity of water as
possible and allowed to stand or settle, the scum being then skimmed off. The
clear liquor is run or siphoned off from the insoluble tarry and other heavy
impurities. This residue of insoluble tarry and other heavy impurities, is then

page_text: filter-pressed, the cakes being removed, mixed up with warm water, and again
filter-pressed.
The clear liquor of considerable strength is mixed with more than an equivalent
weight of sulphate of soda also in strong solution, and suitably settled or filtered,
and the mixture is heated. Sulphate of lime is precipitated and in falling carries
down with it a considerable proportion of the remaining tarry and pyroligneous
matters in the solution of the acetate of lime. The solution is filtered off in the
filter-press and washed with a little hot water to remove acetate of soda retained
by the sulphate of lime in the press.
The solution of acetate of soda, probably of a brownish colour, containing also a
little sulphate of soda, is concentrated by evaporation, and when sufficiently con-
centrated, is set to crystallize. This it readily does, and if even a little Glauber's
salt crystallised out along with the acetate of soda no harm would result in the
next operation, whilst it actually assists in inducing a larger crystallisation of
the acetate.
(2) The crystals are collected, and drained in a centrifugal machine or in other
suitable manner (the mother-liquor being further concentrated for a final crop);
they are then heated in a suitable still of cast iron or other suitable metal or
material, with sulphuric acid of about 140 degrees of Twaddel's hydrometer, in
slight excess over that necessary to form normal sulphate of soda. Thus any
residual adherent colouring matter retained by the crystals, is destroyed and
charted. Acetic acid of considerable concentration and purity distilling over, the
distillation being carried on at as low a temperature as possible. The fact is, as
was discovered after several trials, that on the precipitation or salting out from a
hot solution of the crude acetate of lime, a considerable amount of tarry and
pyroligneous matter becomes included in the but slightly crystalline masses of
acetate of lime separating from the hot liquid. Such tarry and pyroligneous
matters are largely eliminated on the contrary, when the well defined crystals of
sodium acetate separate in the improved method.
Thus, a purer acetic acid results from the distillation of the latter salt with
sulphuric acid than will result by the distillation of a correspondingly formed
acetate of lime by the salting out, or fishing process, already referred to.
(3) The acetic acid obtained by exhaustively distilling the acetate of soda as
described, with sulphuric acid, is next neutralized with lime and carefully
evaporated, when the acetate of lime now salted out and left as a residue will be
found to be nearly quite white and nearly pure, and quite free from the odour of
pyroligneous acid and creosotic matters.
(4) The acetate of lime is now dissolved in water to form a strong solution and
to this is added the calculated equivalent weight of by preference white sulphate of
ammonia also in concentrated solution, and the mixed solution is heated to from
about 60° C. to 80° C. By the double decomposition ensuing, sulphate of lime is
formed and precipitated, whilst acetate of ammonia remaine in solution. It has
been found that what little tarry or pyroligneous and colouring matters do remain
in the acetate of soda, will now be precipitated along with the sulphate of lime,
and thus a clear, colourless, and almost pure solution of acetate of ammonia will be
formed, and can be at once, after proper dilution to the required strength, used for
the treatment of the litharge in the white lead process referred to in Patents 16093
of 1890 and 5501 of 1891.
(5) The crystalline residue of sulphate of soda and carbonaceous residue, left
after treating the acetate of soda with sulphuric acid and distilling as described, is 5
treated with a small quantity of water, the carbonaceous matter let settle or filtered
off, and the solution is evaporated and crystallised, the Glauber's salt being then
used over again in the process for treating the grey acetate of lime in the first
stage of this process, whilst the sulphate of lime or gypsum, obtained by the double
decomposition in the final stage, by the action of the purified acetate of lime on 5
sulphate of ammonia, may be calcined and converted into plaster of paris,
cements, &c. and so no loss be incurred.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
In connection with the process of manufacturing white lead or basic carbonate of
lead in which the action of acetate of ammonia upon oxide of lead (litharge or
massicot) forms the distinguishing feature, or similarly of acetate of ammonia in
contact with metallic lead in any electro-chemical process, the process as described
for manufacturing acetate of ammonia in a sufficient degree of purity for the
purpose described.
WATSON SMITH.