CERTAIN IMPROVEMENTS IN THE MANUFACTURE OF THE OXIDES OF LEAD, AND ALSO OF THE CARBONATE OF LEAD
Year: 1838

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
WATT, of Manchester, in the County of Lancaster, Lecturer on Chemistry,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Fifth day of January, in the first year of Her reign, and in
the year of our Lord One thousand eight hundred and thirty-eight, did, for
Herself, Her heirs and successors, give and grant unto me, the said Charles
Wattand'l homas Rainforth Tebbutt, of the same place, Merchant, Herespecial
licence, full power, sole privilege and authority, that we, the said Charles Watt
and Thomas Rainforth Tehbutt, our executors, administrators, and assigns,
and such others as we,the said Charles Watt and Thomas Rainforth Tebbutt,
our executors, administrators, or assigns, should at any time agree with, and no
others, from time to time and at all times during the term of years therein
mentioned, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, our Invention of
CERTAIN IMPROVEMENTS IN THE MANUFACTURE OF THE OXIDES OF LEAD, AND ALSO
OF THE CARBONATE OF LEAD;" in which said Letters Patent is contained a
proviso, obliging us, the said Charles Watt and Thomas Rainforth Tebbutt, by
an instrument in writing under our hands and seals, or under the hand and
seal of one of us, particularly to describe and ascertain the nature of our said
Invention, and in what manner the same is to be performed, and to cause the

page_text: same to be inrolled in Her Majesty's High Court of Chancery within six
calendar months next and immediately after the date of the said in part
recited Letters Patent, as in and by the same, reference being thereunto
had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Charles Watt, on behalf of myself and of the said Thomas Rainforth Tebbutt,
do hereby declare that the nature of our said Invention, and the manner
in which the same is to be performed, are particularly described and ascer-
tained in and by the following description thereof (that is to say) :-
I would first remark, that as carbonic acid does not combine with inetallic
lead when these bodies are placed in contact with each other, it is necessary
that the lead should be converted into a protoxide, and subsequently into a
carbonate, and as this fact is well known to all practical chemists, I shall
proceed to describe our improvements in the manufacture of the oxides of
lead, and also of the carbonate of lead, which consists of three different
improved processes for obtaining the white hydrate of protoxide of lead, and
converting the same into carbonate of lead; and I shall therefore describe
these processes separately, and the manner of effecting the objects of our
improvements.
Firstly, the metallic lead is to be converted into a protoxide or litharge in
the usual way of manufacturing the said oxide, in which state it may be
purchased as an article of commerce, or manufactured as required; or we
produce a hydrate of protoxide in the following manner:-We boil the
protoxido or litharge with either of the chlorides of sodium, potassium, or
barium in a state of solution, in a suitable iron or wooden vessel, heated by
steam pipes or any other convenient manner, until the chlorine in these
substances has passed into the oxide of lead, which is thereby converted into
chloride of lead, which becomes perfectly white when the process is properly
conducted and perfected. Having now obtained the chloride of lead, we
proceed to produce the hydrate of protoxide from the same, by expelling the
chlorine by means of sulphuric or nitric acid, thereby converting the chloride
of lead into a protoxide of lead, combined with either of these acids, which we
effect in the following manner:-We take the chloride of lead prepared as
above stated, and red oxide (usually called red lead), in the proportions of
three-fourths of the former to one of the latter; these are placed in a suitable
vessel or retort, and to them is to be added concentrated sulphuric acid, in
weight equal to about one-third of the whole chloride and red oxide, and we
then apply a gentle heat thereto by means of steam, or in any other convenient
manner, which heat is to be continued until all the chlorine is expelled, and

page_text: the red oxide converted into a white sulphate. The vessel in which this
operation is to be performed may be of cast iron with an earthenware head, so
constructed that the chlorine thus formed may pass into an apparatus such as
is usually employed in making the chlorides of lime, soda, &c., such apparatus
being varied according as the chlorides are intended to be made or formed in a
dry orliquid state; we then remove the sulphate which has thus been produced
into a wooden vessel or tub furnished with a cover, and well wash it with
lime water, in order to remove therefrom any uncombined sulphuric acid,
letting the waste water run off until that remaining with the sulphate is free
from acid; we then add by degrees and at intervals of about ten minutes a
solution of some alkaline or carthy carbonate, choosing such of the latter as
are soluble in sulphuricacid, more particularly alumina and magnesia. While
adding the solution of alkaline or carthy carbonate, we frequently or con-
tinually stir the mixture, continuing the process of pouring in the solution so
long as any effervescence continues. The sulphate of lead has now become a
white hydrate containing much carbonate. In order to ensure perfect con-
version of the whole into carbonate, we cause a current of carbonic acid to
pass into the precipitate or mixture, and continue it for about an hour, keeping
the vessel in which the operation is performed nearly closed or covered with
slight pressure on the lid, in order to obstruct the escape of the gas,the whole
being occasionally agitated or stirred by any suitable means; the usual Woolf's
apparatus is best calculated for this operation, and may be made of wood or
earthenware. We generate carbonic acid gas in the usual way adopted for
such purposes, which is too well known to require particular description.
We then again wash the precipitate or what may now be called white
lead several times with clear water, in order to remove therefrom the salts
which have been formed by the chemical action; the process is now complete,
and the white lead fit for use.
In our second process we proceed as follows:-We take chloride of lead
and place it in an earthenware vessel or such other material as is not acted
upon by nitric acid, and which is furnished with suitable conducting-off pipes
and receiving vessels. The chloride of lead is here subjected to the action of
nitric acid equal in weight to about one-fourth of the chloride (which may be
either concentrated or diluted to one-half or two-thirds of its formerstrength),
adding fresh acid so long as any chlorine passes off from the chloride of lead
into the vessels destined to receive it. The retort or vessel containing the
chloride of lead and nitric acid must be furnished with all necessary pipes for
applying the acid and conducting off the gas, and, as before stated, is to be
constructed of earthenware, glass, or such other material as is not acted upon

page_text: by the acid. This process leaves the load in the state of hydrate of protoxide
combined with a small portion of nitric acid, which hydrate of protoxide is to
be converted into carbonate of lead after the manner stated in the process
first described, that is, beginning with the solution of alkaline carbonate.
Our next or third process is as follows:-We first dissolve metallic lead
finely granulated or its protoxide in nitric acid diluted in about eight parts, by
weight, of water in a suitable vessel, as above stated, and apply a gentle heat
thereto by means of steam or in any other convenient manner until all the
lead is dissolved; we then precipitate the lead by any of the well-known
alkalies or earths in their caustic state. We prefer lime and barytes, because
by adding sulphuric acid to them they will be precipitated in the solid form,
leaving the dilute nitric acid free to be applied to other useful purposes; we
also use acetic acid for dissolving the protoxide of lead, following the same
course as with nitric acid. After the precipitate or hydrate of protoxide of
lead has been thus obtained, it is to be well washed with clean water in order
to remove therefrom the alkali or earthy salt formed by the chemical com-
bination. The precipitate is now a white hydrate of protoxide of lead; we
then cause a stream of carbonic acid gas to pass into the hydrate of protoxide
by means of the well-known apparatus called Woolf's apparatus, which is
formed of earthenware or wood. The carbonic acid gas is generated or
obtained in the usual or common method. The current of carbonic acid
gas upon the white hydrate of lead is to be continuous or nearly so, and the
mixture is to be agitated by frequently stirring the oxide during the opera-
tion, which will be much facilitated if the hydrate and water are kept at
about the temperature of 120 degrees.
In our improved process we avail ourselves of thecombination of the
protoxide of lead, which takes place when it is boiled with oily and fatty
bodies until they are converted into oleates, margarates, and stearates, which
conversion or transformation is as well effected by oxide of lead as by any of
the alkalies or earths; we then displace the protoxide of lead by an alkali or
earth, or their carbonates, which yield carbonic acid to the lead while the base
combines with the fat acids, a stream of carbonic acid gas being applied to the
materials under operation, as before stated, for about an hour in order to insure
the perfect transformation of the protoxide of lead into carbonate of lead,
which carbonate is to be well washed from all adhering salts or other extraneous
matters, as before stated; or we may use dilute sulphuric acid, and boil the
mass until all the protoxide of lead is precipitated as a white sulphate, which
is to be formed into a carbonate, as already described.
In the foregoing processes we do not claim the use of nitric acid or acetic

page_text: acid as solvents of lead or its protoxides for the purpose of forming white lead,
but we claim the use of sulphuric acid for converting the chloride of lead into
a hydrated protoxide of lead and afterwards into a carbonate of lead, and also
the chloride of lead thus used. We likewise claim the precipitating the oxide
of lead from the nitric and acetic acids by caustic alkalies or earths instead
of the carbonates, and afterwards removing them and washing the precipitate
before we form them into a carbonate of lead; and we claim the forming
the bydrate protoxide of lead, from whatever acid it is precipitated, into a
carbonate of lead, and not, as in the common way, precipitating it from
a solvent by means of carbonates of alkalies. We also claim the use of such
particular earths as lime and barites, as the nitric and acetic acids may be
removed from them by the mere application of as much sulphuric acid as will
just saturate the lime or barites, and so that these acids may then be employed
for other useful purposes; we likewise claim the application of hydrate of
protoxide of lead formed, as described, from sulphate or hydrate of lead, for
the purpose of being converted into a carbonate, and likewise the passing a
current of carbonic acid gas through the hydrate to effect its thorough
transformation into carbonate; we likewise claim the use of the oleates,
margerates, and stearates of protoxide of lead as substitutes for acetic acid
and other acids in the production of carbonate of lead or white lead for the
purpose of converting the hydrate of protoxide of lead into carbonate of lead.
In witness whereof, I, the said Charles Watt, have hereunto set my
hand and scal, this Fifth day of July, in the year of our Lord One
hundred and thirty-eight
CHARLES (L.s.) WATT.
AND BE IT REMEMBERED, that on the Fifth day of July, in the second
year of the reign of Her Majesty Queen Victoria, the said Charles Watt
came before our said Lady the Queen in Her Chancery, and acknowledged
the instrument aforesaid, and all and every thing therein contained and
specified, in form above written. And also the instrument aforesaid was
stamped according to the tenor of the Statute made in the fifty-fifth year of
the reign of His late Majesty King George the Third.
Inrolled the Fifth day of July, One thousand eight hundred and thirty-