Improvements in or Appertaining to the Manufacture of Peroxide of Lead or Alkaline Plumbate and Bye-products.
Year: 1889

page_text: Date of Application, 27th July, 1889
Complete Specification Left, 28th Apr., 1890-Accepted, 27th Aug.,
1890
PROVISIONAL DIECIFICATION.
Improvements in or Appertaining to the Manufacture of Peroxide of
Lead or Alkaline Plumbate and Bye-products.
I, L'AUL NAEF, of Dyar Terrace, Winnington, Northwich, in the County of Chester,
Doctor of Philosophy and Practical Chemist, do hereby declare the nature of this
invention to be as follows
:-
.
In all the processes which are at present employed for the manufacture of peroxide
of lead. the ordinary oxule or a salt of lead is treated with chlorine or an oxidizing
compound of the said element.
L
The principal object of the present invention is to effect the oxidation of oxide of
lead to peroxide in a more economical manner than has been hitherto possible. I either
employ ordinary nitrate of sod or other nitrates for the purpose of oxidizing PbO
to Ph O,, in which case I obtain, at the same time, nitrites as very valuable by
products, or I effect the oxidation by atmosphene oxygen directly. In both cases
do not, as in all the processes at prosent known, produce peroxide of lead directly,
but I first get, as intermediary product, a compound of peroxide of lead with an oxide
of an alkali or alkali earth metal, and it is this product from which, afterwards,
peroxide of lead is separated. As raw material I usually employ oxide of lead either
in the shape of luharge such as it is obtaine as a by product from leal works, or
produced on purpose by the decomposition of various salts of lead, such as the sulphate
or the chloride, by means of caustic soda or other bases, in a manner well understood.
Carbonate of lead may also be employed after having been converted into oxide by
subjecting to a high temperature If desirable, metalhe lead may also be employed
in this state as a raw material for the manufacture of peroxide-of lead.
The oxidation by means of nitrate of soda or other nitrates is especially advan-
tageous in places where the nitrite obtained as a by product is easily disposed of.
I then proceed as follows:-
Nitrate of soda together with caustic soda, is melted in a pot, and metallic lead (in
a granulated state) or oxide of lead, is slowly introduced. An oxidizing action takes
place unmediately, and at a comparatively low temperature plumbate of soda of
yellowish colour is formed. When the oxidation is completed the melted mass is lett
to cool. It is then exhausted with water or dilute caustic liquor, and the plumbate of
soda, which is nearly insoluble in water, is purified by washing with cold water.
order to convert the plumbate of soda into peroxide of lead the former is decomposed
by heating with water, or by means of carbonic acid or another acid exactly in the
same manner as the plumbate produced by direct oxidation with air, as will be described
later on.
In
The liquors containing nitrites and caustic soda are concentrated by evaporation,
and after addition of nitre and of a quantity of caustic soda, equivalent to the amount
removed by the plumbate, it is used over again for the oxidizing process. This may
be repeated, if desirable, till the proportion of nitrite and caustic soda is such as to
make it advantageous to work the liquors for nitrite. For this purpose the caustic soda
is converted into carbonate by means of carbonic acid, which at the same time causes
all the lead to be precipitated. The clear liquor is evaporated and the soda is fished
out as monohydrated salt during evaporation, or it is separated by crystallization.
The mother liquor containing nearly all the nitrite is further treated with carbonic
acid, in order to precipitate any soda dissolved as bicarbonate.
.
The separation of nitrite from caustic soda may also be effected without converting
all the caustic soda into carbonate. For this purpose the liquors are concentrated
to a suitable strength and afterwards left to cool, when nearly all the nitrite is precipi-
tated
The strong caustic liquor is sy phoned off and evaporated further. The impure

page_text: nitrite is dissolved in water and purified by treating it with carbonic acid in the afore
described manner.
If metallic lead is used as raw material, the oxidation may he carried out in two
stages. The metallic lead is firstly oxidised by quantity of mtrate of soda.sufficient
to form oxide of lead without addition of caustic soda. Tho melted mass is lixiviated,
when half of the nitrite is obtained in a perfectly pure state at once. The oxide of
leads afterwards further- oxidised by nitrate of soda together with caustic soda, in
the afore described manner. Instead of in presence of caustic soda, the oxidation with
nitrates may also be effected in presence of other oxides of alkaline-oralkaline earth.
metals...
=
When the oxidation of oxide of lead is to be-effected directly-by atmospheric
oxygen, oxide of lead is thoroughly mixed with an alkali or alkaline earth, or with
mixtures of such alkalies or earths, and the mixture is afterwards exposed to a curient
of air at a suitable temperature. By this treatment atmospheric oxygen is pretty
readily absorbed, and a compound of peroxide of lead with the oxide employed, a so
called plumbate, is formed, just as is the case, when effecting the oxidation by means
of, nitrate of soda. In some cases metallic lead may also be employed for direct
oxidation with air.
If alkaline earths are employed in the process, the proportion of oxide of lead and
the alkaline earth should he chosen in such a manner, that the resulting mixture
remains perfectly solid at the temperature of oxidation. To obtain a very intimate
mixture, the alkaline earth may be slaked with water, and after adding the oxide of
lead the mixture is dried. The oxidation is advantageously carried out in a closed
roaster or in muffles, with easy access of air. The product which is obtained by this
treatment is sold as such, or it is converted into peroxide of load by addition of
an acid,
4
I generally prefer employing an alkali, especially caustic soda. I then proceed as
follows:-
-:
Caustic soda is melted in a vessel made of iron or another metal. which is chiefly
heated at the sides and less so at the bottom. After covering the vessel with a suitable
cover, a gas distributor is introduced, and air, which is preferably heated beforehand,
is forced through the molten mass. Now the requisite quantity of oxide of lead or
metallic- lead is gradually added in small portions The oxidation progre-ses pretty
rapidly, and the plumbate of soda forined is kept floating in the molten caustic in a
very fine state of division by the current of air. After the reaction has advanced so
far that only a few per cent. of the oxide of lead originally employed is loft unchanged,
the current of air is stopped, the gas distributor is removed, and the melted mass is
left to settle for a short time. In order to complete the oxidation a little chlorate of
soda may be added.
The plumbate of soda settles rapidly in the melted caustic soda, and a large pro-
portion of the caustic primarily employed can therefore be scooped or run off into
another pot. This portion contains only very little plumbate and is at once ready for
the treatment of a further quantity of oxide of lead. The plumbate of soda loit
behind still contains a considerable quantity of caustic soda. It is scooped out into
an iron vessel, where it is left to solidify. Afterwards it is bioken up into small pieces
and is lixiviated first with dilute caustic soda liquor and later on with water. The
strong caustic solution obtained by this operation is evaporated down in pans, which
are heated by waste hear. The liquors do not contain much plumbate in solution and
the solid caustic resulting after evaporation can therefore be employed for the treatment
of further quantities of oxide.
The plumbate produced by the oxidation of metalhe lead or oxide of lead with
nitiates or atmospheric oxygen as afore described, may be sold m the dry state with
about 70 per cent, of, peroxide. Usually it will be converted into peroxide of lead,
and the alkaline base, which it contains, is simultaneously recovered for further use in
the process.
For conversion into peroxide the plumbate is heated with water or with a dilute
solution of caustic soda and is, for some time, kept at a suitable temperature. By

page_text: this treatment the plumbate is split up into peroxide and caustic soda. When the
strength of the caustic solution has becoine stable it is allowed to settle and the clear
portion is drawn off from the deposit. In order to complets the decomposition, the
peroxide may he treated a second time with a more dilute solution of caustic soda or
with water. To facilitate the reaction, and to make it succeed in more concentrated
solutions, carbonic acid gas may be passed into the solution. But in this case the
resulting carbonate of sola must be converted into hydrate before it can enter again
into the process.
If the peroxide of lead contains some unchanged oxide, the latter may be oxidized
by adding a little bleaching powder or other hypochlorite, or it may be extracted by
nitric acid.
The peroxide of lead resulting from the decomposition of the plumbate has different
properties according to the temperature and the strength of the caustic liquor employed.
By boiling the plumbate with a rather strong caustic solution very dense peroxide of
nearly black colour is produced. If only a very weak solution an a moderate tem-
perature are employed, a more voluminous peroxide of brownish colour is obtained,
which is suitable for most purposes.
If it is of very great importance to obtain the peroxide in a very voluminous and
finely divided state, I proceed as follows:-
Strong caustic liquor, such as is obtained by lixiviating the plumbate, 13 ovaporated
down When it has become highly concentrated, dense peroxide or plumbate is
introduced and the evaporation proceeded with until the mass has become very con-
sistent and changes its colour. By this treatment a very flocculent plumbate is formed,
which has totally different properties from the anhydrous plumbate which is formed
in the melted caustic soda during the oxidation with air or nitre. It is washed first
by dilute caustic liquor and at last with water. Afterwards it is decomposed by treating
it with water, with or without addition of carbonic acid at a suitable temperature, as
described above
The peroxide of lead which is obtained by this treatment is much more voluminous
than that furnished by any other process known. It is therefore exceptionally well
suited for the purification of sulphate of alumina solutions containing iron, and for
many other purposes.
By the same treatment, dense peroxide of lead obtained from any other source, and
inactive by repeated use, may be convertel into vory voluminous and finely divided
peroxide. The process is also well suited for the recovery of peroxide which has
become dense and inactive by repeated use.
Dated this 26th day of July 1889.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicant.
COMPLETE SPECIFICATION
Improvements in or Appertaining to the Manufacture of Peroxide
of Lead or Alkaline Plumbate and Bye-products.
1, PAUL NAEF, of Dyar Terraco, Winnington, Northwich, in the County of Chester,
Doctor of Philosophy and Practical Chemist, 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 most of the processes which are at present employed for the manufacture of
peroxide of lead, the ordinary oxide or a salt of lead is treated with chlorine or an
oxidising compound of the said element.
The principal object of the present invention is to effect the oxidation of lead or
oxide of lead to peroxide in a more economical manner than has been hitherto possible.
I either employ ordinary nitrate of soda or othor nitrates for the purpose of
oxidising Pb O to Pb O,, in which case 1 obtain at the same time nitrites as very
'

page_text: valuable bye-products, or I effect the oxidation by atmospheric oxygen directly. In
both cases, I do not, as in most of the processes at present known, produce peroxide
of lead directly, but I first get as intermediary product a compound of peroxide of
lead with an oxide of an alkali or alkali earth metal a so called plumbate, and it is
this product from which afterwards peroxide of-lead is separated:
As raw material, I usually employ oxule of lead either in the shape of litharge
such as is obtained as a bye-product from lead works or is produced on purpose by
the decomposition of various salts of lead such as the sulphate or the chlorule by
means of caustic soda or other bases in a manner well understood.. Carbonate of lead
may also be emploved after having been converted into oxide by subjecting to a high
temperature. If desirable, metallic lead may also.he employed-in this -state as-a-raw
material for the manufacture of peroxide of lead.
The oxidation by means of nitrate of sola or other nitrates is especially advantageous
in places where the nitrite obtained as a bre-product is easily disposed of.
For the manufacture of plumbate of sodium, I then proceed as follows :-
Nitrate of soda together with caustic soda is heated in a pot and metallic lead (in
granulated state) or oxide of lead is slowly introduced. An oxidising action takes
place immediately and at a comparatively low temperature, and plumbate of sodium
of yellowish colour is formed. When the oxidation is completed, the melted mass is
left to cool. It is then exhausted with water or dilute caustic liquor and the plumbate
of soda, which is nearly insoluble in water, is purified by washing with cold water.
In order to convert the plumbate of soda into peroxide of lead, the former is decom-
posed by heating with water, or by means of carbonic acid or another acid exactly in
the same manner as the plumbate produced by direct oxidation with air as will be
described later on.
The liquor containing nitrite and caustic soda is concentrated by evaporation and,
after addition of nitre and of a quantity of caustic soda equivalent to the amount
removed by the plumbate, it is used over again for the oxidising process.
This may
be repeated, if desirable, till the proportion of nitrite and caustic soda is such as to
make it advantageous to work the liquors for nitrite. For this purpose, the caustic
soda is converted into carbonate by means of carbonic acid, which, at the same time,
causes all the dissolved plumbate to be precipitated. The clear liquor is evaporated
and the soda is fished out as monohydrated salt during evaporation, or it is crystallised
out by cooling. The mother liquor, containing nearly all the nitrite, is further
treated with carbonic acid, in order to precipitate any soda left in solution, as
bicarbonate.
The separation of nitrite from caustic soda may also be effected without converting
all the caustic soda into carbonate. For this purpose, the liquors are concentrated
to a suitable strength and afterwards left to cool, when nearly all the nitrite is pro-
cipitated. The strong caustic liquor is syphoned off and is used again in the process
after evaporation. The in pure nitrite is dried and washed in a centrifugal or on a
filter with water or a concentrated nitrite solution, or it is dissolved in water and
purified by treating the solution with carbonic acid in the aforo described manner
The
If metallic lead is used as raw material, the oxidation may be carried out in two
stages The metallic lead is firstly oxidised without addition of caustic soda by a
quantity of nitrate of soda sufficient to form oxide of lead. The melted mass is
lixiviated, when half of the nitrite is obtained in a perfectly pure state at once.
oxide of lead is afterwards further oxidised by nitrate of soda together with caustic
soda in the afore described manner. Instead of in presence of caustic soda,
the oxidation with nitrates may be carried out in presence of oxides of potassium,
calcium, barium and strontium, in which case the corresponding plumbates are
obtained.
When the oxidation of oxide of lead is to be effected directly by atmospheric
oxygen, oxide of lead is thoroughly mixed with caustic soda or the hydrate of another
alkali or with mixtures of such alkalies, and the mixture is afterwards exposed to a
current of air at suitable temperature. By this treatment, atmospheric oxygen is
pretty readily absorbed, and a compound of peroxide of lead with the oxide of the

page_text: alkalı employed, a so called plumbate, is formed, just as is the case when effecting the
oxidation by means of nitrate of soda.
I generally prefer employing caustic soda I then proceed as follows:-
Caustic soda is melted in an iron vessel, which is chiefly heated at the sides and
less so at the bottom. After covering the vessel with a suitable cover, a gas distributor
15 introduced, and air, which is preferably heated beforehand, is forced through the
molten mass. Now the requisite quantity of oxide of lead or metalle lead is gradually
added in small portions. The oxidation progresses rapidly and the plumbate of soda
formed is kept floating in the molten caustic soda in a state of very fine division by
the current of air. After the reaction has advanced so far that only a few per cent.
of the oxide of lead originally employed is left unchanged, the current of air is
stopped, the gas distributor is removed and the melt is left to settle for a short time.
In order to complete the oxidation. a little chlorate of soda 'may be added. The
plumbate of soda settles rapidly, and a large proportion of the cau-tc soda primarily
employed can therefore be scooped or run off into another pot. This portion contains
only very little plumbate and is at once ready for the treatmnt of a further quantity
of oxide of lead The plumbate of soda left behind contains a considerable quantity
of caustic soda It is scooped out of the pot into un iron vessel, where it is left to
solidify Afterwards it is lixiviated. first with dilute caustic soda liquor, and later on
with water. The strong caustic solution obtained hy this operation evaporated
down in pans, which may be heated by waste heat The liquors do not contain much
plumbate in solution and the solid caustic resulting after evaporation can therefore be
employed for the treatment of further quantities of oxide.
The plumbate produced by the oxidation of oxide of lead or metallic lead with
nitrates or atmospheric oxygen as afore described may be sold in the dry state
containing about 70 per cent. of peroxide. Usually it will be converted into peroxide
of lead and the alkaline base, which it contains, is simultaneously recovered for further
use in the process.
For conversion into peroxide, the plumbate is heated with water or with a dilute
solution of caustic soda and is for some time kept at a suitable temperature. By this
treatment, the plumbate is split up into peroxide and caustic soda. When the strength
of the caustic solution has become stablo, it is allowed to settle and the clear portion
is drawn off from the deposit. In order to complete the decomposition, the peroxide
may be treated a second time with a more diluted solution of caustic soda or with
water. To facilitate the reaction and to make it succeed in more concentrated solutions,
carbonic acid gas or other acids may be passed into the solution. But in this case, the
resulting carbonate must be converted into hydrate before it can again enter into the
process. If the peroxide of lead contains some unchanged oxide, the latter may be
oxidised by adding a little bleaching powder or another hypochlorite, or it may be
extracted by nitric acid.
The peroxide of lead resulting from the decomposition of the plumbate has different
properties according to the temperature and the strength of the caustic liquor employed.
By boiling the plumbate with a rather strong caustic solution, very dense peroxide of
nearly black colour is produced. If only a very weak solution and a moderate
temperature are employed, a more voluminous peroxide of brownish colour is obtained,
which is suitable for most purposes.
If it is of very great importance to obtain the peroxide in a very voluminous and
finely divided state, I proceed as follows:-
Strong caustic soda liquor, such as is obtained by lixiviating the plumbato, is
evaporated down. When it has become highly concentrated, dense peroxide of
plumbate is introduced and the evaporation proceeded with until the mass becomes
very consistent and changes its colour. By this treatment, a very flocculent plumbate
is formed, which has different physical properties from the anhydrous plumbate, which
is formed in the melted caustic soda during the oxidation with air or nitre. It is
washed first with dilute caustic liquor and at last with water. Afterwards it is
decomposed by treating it with water, with or without addition of carbonic acid or
another acid, at a suitable temperature as described above..

page_text: The peroxide of lead, which is obtained by this treatment, is much more voluminous
than that furnished by the other processes in use at present. It is therefore
exceptionally well suited for the purification of sulphate of alumina solution containing
iron and for many other purposes.
By the same treatinent, dense peroxide of lead obtained from any other source may
be converted into very voluminous and finely divided peroxide.
This part of the process is also well suited for the recovery of peroxide, which bas
become dense and inactive by repeated use.
==
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, -I- declare that what-I-
claim 15 -
1. The manufacture of plumbates of alkaline and alkaline earth motals, particularly
of plumbate of sodium and nitrites as bye-products by the oxidation of metallic lead
or oxide of lead by means of nitrate of soda or other nitrates in presence of caustic
soda or oxides of other alkaline or alkaline earth metals, substantially as herein before
described.
2. The manufacture of plumbates of alkaline metals (potassium and sodium)
particularly of plumbate of sodium by blowing air through a mixture of oxide of lead
and such alkaline oxide at elevated temperature.
3. The decomposition of plumbate of alkaline metals, potassium or of sodium,
(particularly of sodium) by heating them with dilute caustic liquor or with water,
with or without addition of carbonic acid or other acids.
4. The manufacture of sodium plumbate and peroxide in extremely voluminous
and finely divided state by heating dense peroxide or sodium plumbate with highly
concentrated caustic soda solution, substantially as hereinbefore described.
Dated thin 15th day of Annil 1900
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, and London, Patent Agents.