IMPROVEMENTS IN, APPLICABLE FOR, OR APPERTAINING TO THE MANUFACTURE OF WHITE LEADPARATION OF
Year: 1882

page_text: LETTERS PATENT to Arthur, James, Smith of 427 Fulham Road West
Brompton in the County of Middlesex for an Invention of "IMPROVEMENTS
IN, APPLICABLE FOR, OR APPERTAINING TO THE MANUFACTURE OF WHITE LEAD
PROVISIONAL SPECIFICATION left by the said Arthur James Smith at the
Office of the Commissioners of Patents on the 15th September 1882.
ARTHUR JAMES SMITH, of 427. Fulham Road West Brompton in the County of
Middlesex, "IMPROVEMENTS IN, APPLICABLE FOR, OR APPERTAINING TO THE
MANUFACTURE OF WHITE LEAD AND TO THE PRELIMINARY PREPARATION OF THE
LEAD THEREFOR
"
In the only method of white lead manufacture hitherto successfully used solid
or perforated plates of lead are exposed to corrosion, and when in large part
corroded the white lead is scraped off them. This handling and scraping is very
deleterious to the operatives, some of whom die from the effects of the lead on their
systems, often contracting their fatal dose of poisoning within a very few weeks of
their first engagement, though the actual illness may last much longer. Now by
this invention I obviate this scraping altogether. The invention consists in
presenting the lead with an enormously extended surface and small thickness to
the extremely slow chemical action of the gases employed in carbonating, and relates
both to the preparation, of the lead so as to obtain this extended surface and to the
conversion of the lead into Carbonate. The actual reactions that occur in this
process are the same chemically as those in the ordinary tan process but
mechanically the process differs widely, and occupies much less time than the
old one.
I reduce the lead to a fine and very open sponge, or tangled mass of fibres of
metal preferably by casting the lead into cylindrical ingots and turning or cutting
it in a lathe or other suitable tool but it may also be made in the form of fine
wires by rolling or by pressing the hot lead through a perforated plate pretty much
as weldless lead pipes are formed or by aspirating a stream of liquid lead by

page_text: precipitation or granulation, by blowing with high pressure jets of air or steam;
but turning is preferable for the reason that a metallic tool thread shaving can be
entangled so as to be far more open, for the slow chemical action of the then freely
circulating gases, than by any other mode of aggregation of particles.
This lead sponge is placed in a chamber to which air (preferably heated) acetic
acid vapours, and furnace gases, (carbonic acid) cooled and purified from sulphur
and other impurities, have access in the well-known proportions of the chemica!
components of the finer white leads.
By aid of the unlimited surface the shredded lead offers to these gases this action
can be made to take place more slowly than in the old process but yet penetrate
the slender substance of the sponge in much less time, and with more perfect
regularity than the greater thicknesses of metal in the old tan heap process.
This new process dispenses with the costs.
1st of collection of tan,
2nd of building up the heap
3rd of taking down the same, and
4th of disposing of the spent tan; and instead of these costs incurs only that of
engine fuel and labor for driving the lead shredding machinery and pumps. The
same fuel (without extra cost) also furnishes carbonic acid which is taken from the
fire-box.
In the above description of my invention, I have given the most rapid method
of manufacture. In some of the chemical processes where carbonic acid is largely
given off in a damp and heated state, such as in breweries or in the Ammonia-soda
process (in reduction of the bi-carbonate) these moist gases can be utilised in
the converting chamber containing the lead wool, instead of escaping at once into
the air.
Thus
But there are other ways of working my process in a slower manner.
the lead wool can if desired be converted into a very fine sample of white lead by
the free access into the converting chambers of the carbonic acid of the atmosphere
which has been found sufficient to entirely corrode the finer fibres of the lead in
a longer period.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Arthur James Smith in the Great Seal Patent Office on the
14th March 1883.
ARTHUR JAMES SMITH of 427 Fulham Road, West Brompton, in the county of
Middlesex "IMPROVEMENTS IN,
APPLICABLE FOR, OR APPERTAINING TO THE
MANUFACTURE OF WHITE LEAD AND TO THE PRELIMINARY PREPARATION OF THE
LEAD THEREFOR
"
In all existing successful processes of manufacturing white lead the lead in the
form of sheets, bars, or other thick articles is exposed to air vapour of water.
carbonic acid and the vapour of acetic acid, in dung piles, boxes jars or tan heaps.
and when a considerable thickness has been corroded the white lead formed is
scraped off. Other less successful plans that have been proposed consist in granu-
lating the lead and exposing it to acetic acid vapour with carbonic acid either in.
water or in a moist condition. The result in all these cases is a white lead con-
sisting very largely or in some cases entirely of minute, hard, flat, transparent,.
tabular crystals of carbonate of hydrated oxide of lead together with usually a
small admixture of opaque, white, non-crystalline tricarbonate of lead. Now it is
this tricarbonate alone which forms the covering capacity or "body" of the paint..
Painting with the transparent crystals of carbonated hydrate is like painting
with white sand or say sulphate of barium-an article of crystalline texture
having no body or covering power but used largely to adulterate white lead.
It is obvious that if a way could be formed for converting the lead into the
anhydrous fully carbonated and non-crystalline material instead of into transparent
crystals of hydrated carbonate thinly coated over with or having thinly interspersed
with it a little of the non-crystalline tricarbonate, an enormous advantage would
accrue and this advantage I obtain by my process. Again by the existing
successful processes, immense quantities of refuse tan or dung have to be collected
and used the highly poisonous white lead has to be scraped from the metallic
lead to the imminent danger to the lives or at least to the constitutions and health
of the employés but with my process no extraneous material such as tan'or dung
is required-and beside the enormous saving of expense thereby-there is the
additional advantage that the white lead has not to be handled in my process
until in a completed state it is ready to be mixed up with oil into a finer white lead
than hitherto known to commerce and thus all danger to the health or lives of the
employés is avoided.
Now my process consists first in laminating the metallic lead and forming it into
a light open wool itself penetrated with innumerable minute cracks, and then
passing through it carbonic acid and air just sufficiently damp to be able to act
with extremly slow corrosive action on the enormously extended surface of the
lead so that the lead is formed into tricarbonate at once, and not into a hydrated
carbonate. Now this tricarbonate appears to be formed only on the immediate
surface actually exposed to the carbonic acid and only then when there is not
sufficient moisture to form the hydrated oxide; it is only formed very slowly and
in extremely thin layers. Now if this slower action alone were employed on the
bars or sheets of lead used in the ordinary process or even in ordinary lead wire
it would utterly fail as it would take years, perhaps centuries to permeate the
lead to a sufficient thickness to be scraped off but when the lead (turned into fine
wool say with fibres 3/4 of a millimetre in breadth by 1% of a millimetre in
thickness at the centre and by the act of turning filled with innumerable minute
cracks) has the gases slowly but constantly passed through it bathing all sides of

page_text: the fibres, and permeating the microscopic cracks, in the course of a few months
the fibre is entirely converted into white lead The reason of this in all probability
is that in turning the lead the molecules of the lead turning are violently
disarranged and an infinite number of very minute cracks permeate the lead in all
directions and thus enable the gases to act upon it. A bright surface of lead!
sheeting of the same thickness placed among the turnings is almost unaffected by
these weaker gases necessary for producing my pigment for the reason that this
molecular disturbance and thorough cracking has not taken effect in it Similarly
a sheet of lead can be exposed to the weather for centuries without the formation
of appreciable quantities of white lead, whereas my sponge could not be exposed
to the weather for a year without being entirely corroded If too the gases have
been kept just sufficiently moist to enable the carbonic acid or mixed carbonic and
acetic acids to act chemically on the lead but not sufficiently moist to form the
hydrated carbonate, a nearly pure tricarbonate is the sole result This is especially
the case when the lead wool is exposed to the action of light. To effect this
however it is necessary that the fibres of lead wool should be sufficiently, thin to be
corroded throughout, yet sufficiently thick to stand without alteration of shape
until entirely corroded. They must be entangled sufficiently openly to enable the
gases to permeate them perfectly yet be sufficiently interlaced to form mutual
support This is best done by forming them by turning them in one long
continuous sliver or wire from a cylindrical ingot of lead in a suitable lathe and
allowing the said wire to entangle itself by falling in a pile or into a box as it is
turned off the cylinder.
In carrying my invention into practice I use the apparatus set forth on the
accompanying drawings though it is obvious that the apparatus can be almost
infinitely varied in design.
A is a long chamber like a gardener's hot-bed. B a steam pipe useful to warm
it in very cold weather. C trays of acetic acid or vinegar. D glass covers or roofs
that can be closed or slightly opened so as to regulate the moisture. E portable
trays with pervious bottoms upon which the lead wool is piled to a height of
about 50 millimetres. The bottoms of these trays are supported by legs so that
the air can circulate under them and are formed of thin laths interlacing each
other with wide spaces between. Upon these and supporting the lead wool a layer
of very open canvas or other material can be placed so as to support the material
with as free air passage as possible G is a hygrometer which I usually place in
the lead wool so as to be able to more easily ascertain the degree of dampness,
H is a pipe bringing purified furnace gases to the apparatus these gases are the
ordinary products of combustion of a furnace-the gases from a lime kiln or other
gases consisting largely of air and carbonic acid but purified in any convenient
manner from sulphuretted hydrogen, sulphurous acid, soot, and other deleterious
ingredients and made sufficiently moist by passing over damp sponge or other
extended damp surface. If this surface be damped with weak acetic acid or
vinegar and water there will be no need of the vinegar trays C as already described
The gases aforesaid are pumped over the wet sponges and into the apparatus by
pump, fan or any other convenient apparatus in a constant current not powerful
enough to mechanically act on (that is blow away) the white lead. The action
goes on day and night for a few months until by examination it is found that the
lead is entirely corroded when the trays are lifted out and fresh trays inserted
The use of acetic acid is to expedite the process but I find that even the carbonic
acid naturally present in the air will do the work if a current of air be passed
through the lead wool for a sufficient length of time say for a year or more.
practice however the richer the gases are in carbonic acid up to say equal quantities
of carbonic acid and air-the quicker the white lead is formed.
In
Now it will be seen that the invention practically consists in exposing lead in an
extremely finely divided state to the very slow affinity of carbonic acid and thereby
forming tricarbonate of lead at once instead of forming first a hydrated oxide
and then a hydrated carbonate as in the usual plan. In the ordinary process a

page_text: layer of white lead chiefly hydrated carbonate several millimetres in thickness is
formed in the course of a month or two. In my process a layer of white lead
chiefly or entirely tricarbonate one eighth of a millimetre thick is formed in the
same time and even this layer is in all probability a mass of layers round the
molecular cracks each layer being not one hundredth of a millimetre in thickness.
Also another great point in my invention consists in the forming of the lead by
mechanical means into a tangled wool each fibre by reason of its mode of formation
filled with minute molecular cracks so as to expose an enormously extended surface
of thin lead that will entirely corrode away to the action of very slowly corroding
gas, no part of it being probably a hundredth of a millimetre from one of the
minute molecular cracks.
The difference between my white lead and that made by the ordinary processes
is very striking under the microscope, for whereas the ordinary white lead is
found to be very largely composed of transparent flat crystals like that shown in
Fig 2 with here and there especially in the very outside layer of white lead an
exfoliated mass of perfectly opaque white matter like that shown in Figs 3 or 4,
my white lead (if care has been taken to keep the gases at the right hygrometric
condition) is entirely or in very large part formed of this opaque exfoliated
non-crystalline fully carbonated material shown in Figs 3 and 4.
Having now described my invention and the best mode known to me of carrying
it into effect I wish it to be understood that what I believe to be new and desire
to protect under the herein before in part recited Letters Patent is
1st In the manufacture of white lead the use of lead turnings or planings
substantially as herein described.
2nd In the process of manufacturing white lead exposing the lead in the form of
an open tangled wool of uniform fibres (turned or planed off a mass of lead) to the
slow action of corroding gases.
3rd The manufacture of white lead by means of gases of comparatively extremely
weak power (when compared to those usually employed) acting at infinitesimal
distances substantially as described.
4th As a new or improved manufacture in the realm the white lead formed
almost entirely of the exfoliated absolutely opaque material called in this
specification tricarbonate of lead.
In witness whereof I the said Arthur James Smith have hereunto set my
hand and seal this fourteenth day of March in the year of our Lord one
thousand eight hundred and eighty three.
LAATTTA TINERA AURT