IMPROVEMENTS IN THE MANUFACTURE OF THE OXIDE OF ZINC, AND IN MAKING PAINTS FROM OXIDE OF ZINC
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWIN
PROTHEROE, of Austin Friars, in the City of London, Merchant, send
greeting.
•
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Thirtieth day of
April (One thousand eight hundred and fifty), in the thirteenth year
of Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Evan Protheroe, my exors, admors, and assigns, Her especial
license, full power, sole privilege and authority, that I, the said Evan
Protheroe, my exors, adññors, and assigns, or such others as I, the said
Evan Protheroe, my exors, adñiors, 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 expressed, should and lawfully might make, use, exercise, and
vend, within England, Wales, and the Town of Berwick-upon-Tweed, the
Invention of "IMPROVEMENTS IN THE MANUFACTURE OF THE OXIDE OF ZINC,
AND IN MAKING PAINTS FROM OXIDE OF ZINC," communicated to me from
abroad; in which said Letters Patent is contained a proviso that I, the said
Evan Protheroe, shall cause a particular description of the nature of the said
Invention, and in what manner the same is to be performed, by an instrument
in writing under my hand and seal, to be inrolled in Her said Majesty's
High Court of Chancery within six calendar months next and immediately

page_text: 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, J, the said
Evan Protheroe, do hereby declare that the nature of the Invention com-
municated to me, and the manner in which the same is to be performed,
are fully described and ascertained in and by the following description thereof,
reference being had to the Drawing, hereunto annexed, and to the figures
and letters marked thereon (that is to say):
It is to be observed that the oxide of zinc when manufactured is to be
employed in place of white lead. It is well known that there are great
inconveniences arising to the workmen employed both in the manufacture and
use of white lead, and as it is used as the base of almost all colors the injurious
effects are very great, besides which the colors prepared with white lead
quickly change from the effect of the sulphurous emanations.
It was long
sought to discover a material which might be employed as a substitute for
white lead, and which might be obtained without these injurious consequences;
experiments have been made on the oxides of antimony, bismuth, and tin, but
not with success. Courtois, of Dijon, and the celebrated French chemist, Guiton
Morveau, have stated, previous to One thousand' seven hundred and eighty-
nine, that the o:ide of zinc might be employed without any injury, and would
form much whiter colors and much less liable to change than when mixed
with white lead. About the same time an Englishman of the name of
Atkinson occupied himself in the manufacture of the oxide of zinc, and many
others have since then been engaged upon the subject; but the difficulties
that all have had to contend with (and from which the oxide of zinc has not
been brought into use) are the want of a good material to combine with it so
as to facilitate the drying. The object of this Invention is to manufacture the
oxide of zinc of a finer color and at a less price, and also to combine with it
such materials as will cause it to dry as well as the white lead. The
apparatus to be described is based upon this principle, videlicet, to produce
the oxides without reducing the zinc into vapour or distilling the same. By
the use of this apparatus the oxide will be divided into two qualities, the
lighter portion of it will be carried off and deposited in chambers suitably
arranged to secure it, and the heavier parts will be deposited upon the zine
under operation, from whence it is to be removed as fast as it is formed.
The apparatus by which these processes are carried out is composed of, first,
two large retorts which communicate with each other, in which the zinc is
heated partly by the effect of the heat from the fire and partly by the heat
which results from the combustion of the zinc; and, second, of a reverberatory

page_text: furnace which is heated by the waste heat of the fire which heats the retorts;
and, thirdly, in the arrangement of a series of chambers to collect the light
oxide, and also apparatus for the heavier part to fall into.
In the Drawing, Figures 1, 2, 3, and 4, represent the apparatus for burning
the metal so as to form the oxide; Figure 1 being a longitudinal elevation of
the side of the fire place; Figure 2 a vertical and longitudinal section through
the line A, A, of Figure 3, which is a horizontal section through the line
B, B, of the Figure 2; and Figure 4 is a vertical section through the line G
which cross the Figures 1, 2, and 3. In all these Figures the same letters
are used to indicate the same parts. D, D, and E, E, are two retorts which
are made of fire clay of several pieces connected together, but they may be all
of one piece. F is the fire place placed under the retort D, which are of the
form I prefer, but the same may be varied in form. The flame and smoke of
the fire place pass, first, under the retort D, from thence under the retort E
through the passages G, G, which terminate in the reverberatory furnace
H, H, and from thence up the chimney I, I. J, J, and K, K, are openings
of the apparatus. M is an opening by which there is a communication
between the retort D and the reverberatory furnace H. There should be fire-
proof material to shut this communication when necessary. N is a tube
through which the light oxide passes off into the chamber to receive it.
0, 0, is a door to allow of such tube being cleaned out. P is a valve which
is to be shut when the flue N is being cleaned out. Qis the side valve
which is to be shut when the operations are only going on in the retort D.
a is a tube which communicates with a steam generator, and by the intro-
duction of a jet of steam the withdrawing the oxide into the chambers is
facilitated. R, R, is the chamber into which the heavier oxide is drawn by
the means of the rake shown at Figure 5. S is the passage for the oxide to
pass into the chamber R, where it falls into the metal box T, which is on
wheels so as to be readily moved, which it is to be as it becomes full, but the
use of the box is not indispensable as it may be allowed to fall upon the floor
of the chamber. There is a similar arrangement on the other side of the
apparatus to receive the heavier oxide from the retort E. c, c, are spaces
around the fire where the air becomes heated, and which air is used to oxidize
the zinc; or, in place of air being used alone, it may be mixed with steam and
used together. e, e, are spaces above the retorts which communicate by small
openings with the passage G, so as to allow of the gases which arise from the
fire to pass therein. f, f, are openings in the brickwork of the apparatus
which are closed by means of two bricks. By means of these openings the
passages may be cleaned out, and, in the event of the retort breaking, zinc

page_text: would flow out through them. Figure 6 is a view of an instrument used for
detaching the pieces of oxide which adhere to the bottom of the retorts.
Figure 7 is an instrument for cleaning the retorts out after the other
instrument has been used.
I will now describe the mode of working the apparatus. The retorts are to
be heated up to red heat by coke or other suitable fuel. Afterwards the zinc
is introduced into the reverberatory furnace H. When it is melted it will
flow through the passage M on to the retort D, and from the retort D into
the retort E, through the opening L. That
is to be set to work.
being done, and the zinc
There is to be one of these
sufficiently hot, the rake
rakes to each retort, and they are employed to rake over the surface of the
zinc to remove the heavier oxide in proportion as it is made, and to cause it
to fall into the chamber R through the opening S. From the continued
action of these rakes the following advantages will accrue. First, the oxide
will be produced much whiter in consequence of its being quickly removed.
The color is not affected by its being kept too long in contact with the heat.
Second, a much larger quantity of oxide can be obtained in a given time on
account of the large surface of the oxide, which is constantly in contact with
the currents of hot air which enters through the passages c, c. The air may
be introduced either hot or cold through other orifices. Third, the com-
bustion of the zinc taking place rapidly portion of the heat obtained is
radiated down upon the surface of metal, which assists in the operation, and
thus saves a quantity of fuel. About two thirds of the oxide formed, which is
lighter than the other part, rises up the chimney N, and is drawn by means of
air aided by the jets of steam into the gathering chamber, which I shall
describe hereafter. The arrangements and working of the apparatus may
be modified; for example, the position of the reverberatory furnace may be
changed, and it may be made to communicate with the retort E instead of the
other one.
This arrangement will be found convenient when working with
only one retort, which would be the retort D, and would be supplied by the
retort E, which would be supplied by the furnace H, in which case the
register would be shut. The reverberatory furnace may also be placed on
the other side of the apparatus. And it will be perhaps better to have a small
elevation between the retorts at the lower part of the opening L, so that the
zinc cannot pass by itself from one retort to the other, but when it is required
to pass from one to the other it can be done by means of the rake shewn at
Figure 7.
I will now describe the chambers in which the lighter oxide as it
passes off
is collected in. Figure 8 is a vertical and longitudinal section of theso

page_text: chambers following the line A, A, of the Figure 9, which is a horizontal
section following the line B of the Figure 8; and Figure 10 is a transverse
section following the line G, G, of the Figures 8 and 9. In all these
Figures the same letters are used to indicate the same parts. D, D, D,
are chambers which communicate the one with the other. Any number of
these chambers may be used. The partitions of these chambers are of brick,
and the upper part of them metal, or other materials may be used, but I
prefer these. E, E, are frames covered with metallic cloth, or a thin plate of
metal or wood may be used. It will be seen in the Drawing that there are
two of these frames in each division of the chambers, the one being above
the other, and each is composed of two frames, so that they may be more
readily moved. These frames move upon axes a, a, a. b, b, are rods placed
between the two stages of frames, and assist in supporting them. C, C, C, C,
are cords which pass over pulleys e, e, e, by means of which the frames are
let down, so that the oxide deposited in the top may fall down. It will be
seen in the Drawing that there is a space between one side of them and the
partition of the chamber, which is to allow of the passage of a current of air,
and that the space in one is on the opposite side in the next division. The
arrows indicate the spaces, and the course which the current of air follows
charged with the oxide. The chambers communicate with each by openings
F, F, and by small doors f, f, at the bottom of the partitions. It results from
this mode of communication that the current of burnt air charged with the
oxide arrives at the upper part of the chambers, and passes to the lower part,
and by this means almost all the air within is displaced without mixing, from
whence the result is that the air charged with the oxide is retained a much
longer time, and that this air causes a much larger quantity of oxide to
deposit besides, the frames being placed in a horizontal position, they have
the property of stopping a large quantity of oxide. Practice has proved that
it is advantageous to have these some height, and to increase as much as
possible the horizontal surfaces. G is the chimney, through which the air
escapes after it has been deprived of its oxide. H, H, are doors through
which the oxide is to be removed, which may be done by rakes, as shewn at
Figure 11, or it may fall into boxes, as shewn at Figure 12.
The arrange-
ment of these chambers may be varied; they may be so constructed with
inclined planes, so that the oxide may fall naturally into cases in connection
with the under part of the chambers. It will be preferable to keep these
chambers cool, which may be done by any suitable means. I employ water
for this purpose, continually applied to the upper surface or cover of these
chambers, which, evaporating, cool the chambers.

page_text: I will now describe a machine for bruising or compressing the oxide, which
is made of metal or other suitable material. The heavier oxide which
deposits upon the metal and which is collected into the chamber R, as before
spoken, is not in that state fit to be employed for paints. It is composed of
two parts, the one being, although white, granulous and hard, and the other
soft and fine. The first requires to be bruised and then to be separated from
the granulous part, but this is very difficult to do by means of sieves, but I have
found the oxide, when compressed, can be better packed into the casks, and it
will be found to take a less quantity of oil when it is used for mixing with paints.
This machine will also be found useful in mixing together the drying materials
(to be afterwards described) with the oxide of zinc. Figure 13 is a plan, and
Figure 14 is a vertical section of this machine. Mills and vertical stones
bave long been known, and I only claim the use of them for the preparation
of the oxide of zinc. A, A, is a circular bed in which the conical roller B
turns, motion being given to it by any suitable power attached to the axis G.
a, a, are the rakes which serve to bring the oxide under the middle of the
roller. b, b, is a small sliding plate which is adjusted to the roller when it is
required to empty out the oxide. c, c, is a sliding trap, which is to be drawn
out when the oxide is removed. To increase the friction of the roller upon
the bed of the mill, and to facilitate its operation upon the oxide, I have
reversed the position of the conical roller by having the large diameter of the
roller at the side of the centre of the bed. I have also combined with the
machine a simple arrangement which obviates the necessity of using a sieve.
I cover over the bed or trough, and make a communication with one or more
chambers, and then blow air into the bed by means of any suitable blowing
machine. And this current of air will draw into these chambers all the
lighter particles of the oxide as it becomes crushed. The chambers may be
similar to those described for gathering the light oxide in a very white state.
The heavy oxide which falls into the chamber R (in order to obtain it white)
is to be submitted to the action of sulphuretted alkali, a small quantity of which
is to be thrown over the surface of the zinc, more particularly after each fresh
charge of metal. That which I have found to succeed the best is the per-
sulphate of sodium; or its equivalent of carbonate of soda and sulphuretted
carbonate of soda, and other salts of sodium, will have a good effect; also the
oxides and salts of potassium and calcium may be used, but not with such
results. To bleach the light oxides, which sometimes may be slightly colored,
it be sufficient to dilute it with weak acidulated water. The acids I
may
prefer are sulphuric or acetic, and it is allowed to remain in this acidulated
water for some hours, being stirred from time to time, and afterwards washed

page_text: with pure water and dried, when it will be perfectly bleached. The colors
which are used with oxide of zinc are not found to dry so quickly as those
which are mixed with white lead; generally fatty oils are used as the drying
materials, but they produce injurious effects on the paintings. I have invented
certain drying preparations, which when combined with the oxide will give it
the property of drying as quickly as when the lead is used. The first prepara-
tion is made from umber, and is to be used in its dry state. Umber has
been before used with oils, but in that case they are, to a certain extent,
discolored; but up to this time umber in its dry state has never been used
combined with oxide of zinc to give to it a drying property. I proceed to
prepare it in the following manner:-I take the earth of umber and reduce
it to powder; I then dissolve it over the fire in muriatic acid, and afterwards
concentrate this solution by means of heat until it attains the consistency of
honey or butter; the substance thus obtained is a mixture or combination of
several chlorides with other matters. This may be employed in this state as
a dryer, but it will be found to be highly colored and deliquescent, but I com-
bine it with other matters which increase its drying properties and render it
less deliquescent. What I find best to combine with the chloride of the
umber is resin, and what I prefer is the yellow resin, and this combination I
call a resinate of umber. I dissolve about four parts in weight of the resin
with one part of the chloride, and by this I obtain a resinate of great drying
properties, and these are ground up and mixed with the dry oxide of zinc in
the proportion one part of the resinate to two or three hundred parts of the
oxide of zinc. Another preparation is as follows:-I take one part of the
chlorine of the earth of umber, two parts of chalk or carbonate of lime, four
parts of resin from the yellow pine. These materials are mixed in water and
submitted to a moderate heat and kept stirred and left on the fire until the
chloride and carbonate of lime are completely dissolved, when it will be formed
into a resinate. Instead of employing the earth of umber, previously dissolved
in acids, it may be used in a natural state, but it does not produce so good a
drying material nor so good a color. Another preparation is what I call resinate.
of lead white. I prepare it nearly in a similar manner to the resinate of
umber. I dissolve the oxide of lead in resin or in the salts of lead, such as
the acetate. I generally employ about an equal quantity in weight of the
oxide of lead to the resin; the acetate of lead may also be employed with the
oxide of zinc, but in drying the colors are apt to change their color. The
resinate of lead may be employed in the same way as the resinate of umber
only a small quantity of it is to be used.
Having thus described the nature of the Invention, and the manner of per-

page_text: forming the same, I would have it understood that I do not confine myself to
the details herein described, so long as the peculiar character of any part of
the Invention be retained. And I make no claim to any of the mechanical.
parts separately when not combined or used according to the Invention. But
what I claim is,-
First, the arranging of apparatus in such manner that a constant clean
surface of melted zinc is kept subjected to the action of currents of atmo-
spheric air, parts of the oxides thus produced being raked out of the retort and
part passing away to the chambers, as explained.
Secondly, I claim the peculiar construction and arrangement of the cham-
bers for collecting the light oxide of zinc.
Thirdly, I claim the means herein described of bleaching the oxide of zinc.
Fourthly, I claim the grinding and compressing of the oxides of zinc by a
suitable mill and separating the lighter oxide, as explained.
Fifthly, I claim the manufacture of oxide of zinc into paints by combining
the same with the materials herein described to facilitate the drying of the
same.
In witness whereof, I, the said Evan Protheroe, have hereunto set my
hand and seal, this Twenty-fifth day of October, in the year of our