IMPROVEMENTS IN VESSELS FOR BOILING CHEMICAL PRODUCTS, AS SULPHURIC ACID, AND IN APPARATUS FOR INDICATING THE DEGREE OF CONCENTRATION AND TEMPERATURE OF SUCH PRODUCTS IN THE BOILER, WHICH APPARATUS IS APPLICABLE TO OTHER PYROMETRIC PURPOSES
Year: 1862

page_text: LETTERS PATENT to William Petrie, of Charlton, in the County of Kent,
Gentleman, for the Invention of "IMPROVEMENTS IN VESSELS FOR BOILING
CHEMICAL PRODUCTS, AS SULPHURIC ACID, AND IN APPARATUS FOR INDICATING
THE DEGREE OF CONCENTRATION AND TEMPERATURE OF SUCH PRODUCTS IN THE
BOILER, WHICH APPARATUS IS APPLICABLE TO OTHER PYROMETRIC PURPOSES."
Sealed the 14th November 1862, and dated the 20th May 1862.
PROVISIONAL SPECIFICATION left by the said William Petrie at the
Office of the Commissioners of Patents, with his Petition, on the 20th
May 1862.
I, WILLIAM PETRIE, of Charlton, in the County of Kent, Gentleman, do
I hereby declare the nature of the said Invention for "IMPROVEMENTS IN VESSELS
FOR BOILING CHEMICAL PRODUCTS, AS SULPHURIC ACID, AND IN APPARATUS FOR INDI-
CATING THE DEGREE OF CONCENTRATION AND TEMPERATURE OF SUCH PRODUCTS IN THE
BOILER, WHICH APPARATUS IS APPLICABLE TO OTHER PYROMETRIC PURPOSES," to be
as follows:-
I use a vessel, preferably of a stiff elastic alloy of platinium and iridium,
having its greatest extension in the bottom, which is the surface to be chiefly
heated, and having comparatively very little extension in its sides upwards;
its top part is a dome, or a cone of comparatively thin material, and having a
general relation of outline approaching a hemisphere. The bottom has a
narrow circumferential portion which is horizontal and flat, and rests on a
corresponding flat horizontal ring, preferably of cast iron. The part of bottom

page_text: central to this ring bellies downwards, and in section it is preferably an arc of
an ellipse less than a semi-ellipse, so that it joins and hangs from the
horizontal circumferential portion of the bottom at preferably 45°. The depth
of this central part is only a small fraction of its width. The arrises are not
sharp, but curved. The setting of the vessel is on the ring aforesaid, built
into the furnace above, and surrounding the fire. From outer circumference
of the ring rises a short cylindric portion, to conduct heat from lower part to
prevent overheating, and to heat lower part of sides of boiler with the
desirable regularity and less intensity than bottom; the thicknesses of the parts
of the ring are arranged according to this purpose, and its under part
is bevilled or conical to present a face to the fire.
A continuous inflow and outflow of liquid is intended, regulated by a single
cock at inflow. Inflow is preferably by a funnel trapped by extending straight
into the liquor. Outflow is by overflow through a side pipe, short and
.slanting downwards into a pipe by a slip joint, which carries the liquor to near
the bottom of a cylindric deep-shaped cooler, preferably of same material in a
vessel of water, and having its outflow by overflow action, but drawing the
liquor from bottom. The overflow from the boiler takes place slightly from
liquor next the side pipe in the boiler, but mainly from a "collector," a nest
built against the side, or preferably a vessel fastened in the centre of the
boiler; its rim is above the level of overflow at the side pipe, and is of
considerable lineal extent, to receive the rising fruth or foam, and has a tube
trapped by slanting from the lower part of the collector, and carrying the
liquor into the side overflow pipe. The internal parts most subject to wearing
are coated with gold, and the external parts receiving heat have a "dead"
surface, and are blackened as by platinizing by electric deposition. A cock
preferably of platinum alloy supplies the boiler; the cock is formed so as to
deliver the most liquor in a given time with the least weight of metal; it is
fixed in the end of a leaden pipe, compressed upon a stiff collar carrying teeth,
and fixed upon and forming part of the tube of the cock.
A gauge or indicator is inserted in a hole in the boiler, to show the degree
of concentration of the liquor. This indicator is essentially a spiral made of
laminæ of different metals united flatways; it is attached at its upper end to a
perpendicular hollow cylindric stem, and at its lower end to a light spindle,
passing through the axis of spiral and stem, and having an index or pointer
fixed across its top, double reading to correct errors; this rotates by changes
of temperature, and of concentration of liquor, and shows the degrees of it on
a dial face fixed horizontally on top of the stem. The dial face is graduated
with degrees of hydrometer, and with the chemical equivalents of water in the

page_text: acid intended to be boiled, and with degrees of temperature respectively in
three concentric circles. The lower end of the spindle, which is attached
laterally to the lower end of the spiral, terminates in a point resting in
a hollow at the bottom of a cage, which encloses and protects the spiral, and
is attached to the stem of the instrument. The said spiral may be made in a
manner already somewhat known, but which is incapable of practical accuracy,
except within a limited variation of temperature, owing to the mutual straining
of the metals giving them a permanent set at every such change. I remedy
this fatal defect by employing alloys having but little difference of ex-
pansibility by heat, and at the same time as great elasticity as may be, and
such that the elasticity shall remain in as great a measure as may be at the
highest temperature to which it is to be exposed. Further, I employ more
than two laminæ, united flatways to form the spiral having successively
greater rates of expansion in the order in which they are united, their
successive differences of expansion being made smaller, according as the
intended range of temperature and the accuracy required are greater; and
each lamina is individually thin in proportion, and as many are used as will
give the desired firmness to the spiral.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Petrie in the Great Seal Patent Office on the
20th November 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
PETRIE, of Charlton, in the County of Kent, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of May, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said William Petrie, Her special licence, that I, the said William
Petrie, my executors, administrators, and assigns, or such others as I,,
the said William Petrie, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at
all times thereafter.during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN VESSELS FOR BOILING CHEMICAL PRODUCTS, AS
SULPHURIC ACID, AND IN APPARATUS FOR INDICATING THE DEGREE OF CONCENTRATION

page_text: AND TEMPERATURE OF SUCH PRODUCTS IN THE BOILER, WHICH APPARATUS IS
APPLICABLE TO OTHER PYROMETRIC: PURPOSES," upon the condition, (amongst others),
that I, the said William, Petrie, my executors or administrators, by an
instrument in writing under my, or their, or. one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal::Patent: Office within six calendar months
next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said. William Petrie, do hereby declare
the nature of my ŝaid Invention, and in what manner the same is to be per-
formed, to be particularly:described; and, ascertained in and by the following
statement thereof;: reference being had to the Drawings hereunto annexed;
that is to say:
1.
**
'
The chief points of improvement in the vessel, as it is herein after, described,
are as follows:
_
.:
2.,
First, the heating surface is almost entirely the bottom, not the sides, hence
direct action of fire; and the metál does; not become coated with non-con-
ducting fur or dirt as inside flues; and variations' in the height of. liquor do
not endanger the contact of the fire with parts not covered with liquid within.
Second, the shallow form secures the more speedy evolution of the steam
from the body of the liquor, with the less forcing of the liquor upwards toward
boiling over, and also secures the least hydrostatic pressure, which needs
strength of metal, and aggravates the effects of leakage if it occur.
Third, the same shallowness of liquor also allows the bottom of the vessel
to be made of considerable width without supports or any obstructions (such
as brick arches, &c.) to the free and direct heat of the fire.
Fourth, the mode of setting this vessel is extremely simple and safe, being
on an iron ring, which is formed so as to receive heat, and serve as a heater
to the lower part of the sides. In this way the few. tiles placed on the top of
the ring around.the boiler, are all that are to be removed at any time to take
out the boiler for the purpose of cleaning it out, or for. repairs. This is a
consideration, when the acid-continually fouls' the interior of the boiler, also,
the furnace thus arranged is much more simple than usual..
Fifth, the upper parts of the vessel: not needing, strength to support the
liquor are made thin. The parts subject to special wear inside may be lined
with gold.
i 1
"
Sixth, the sides and top are made of such general form as to cover the
beating surface, and to enclose the greatest space for liquor, and its boiling
froth, by the least surface of platinum.

page_text: Seventh, the vessel. is intended to work with a continuous inflow, and. out-
flow of liquor, regulated by a single. cock (one at the inflow.), while, the out-
flow is by a process of spontaneous overflow, which tends to insure against the
inconveniences of the usual syphon; such. as the liquor being drawn off too
low, or being allowed to rise too high; and thus there is no outflow cock
needing any attention.
Eighth, the overflow is by a slanting nozzle into a pipe, connected by a
spherical slip. joint, a plan which is in practice remarkably efficacious. and
safe, and keeps dry and clean outside. This pipe leads the rectified liquor into
another tube fixed in a small platinum cooler, surrounded by water; and con-
taining a body of comparatively cool vitriol, into which the boiling liquor is
thus merged by being delivered in a divided stream well beneath the surface.
This avoids many inconveniences and expences connected with a long platinum
tube, as a syphon or worm kept cool.
I
Ninth, the overflow nozzle is supplied by a trapped pipe from a collecting
vessel fixed inside the boiler, with the rim at the level at which it is intended
to maintain the boiling liquor. This rim is made of sufficient lineal, extent
to carry off the foam or bubbles so freely into the collector, as in regular
working, to prevent the foam from rising and boiling over. This is a most
important arrangement for tending to a certain fixed level for the liquor; the
boiling of vitriol being an action so difficult to control.
Tenth, the heating surfaces of platinum are made "dead" or rough, and are
platinized by galvanic battery to increase their absorption of heat, while the
other surfaces are well polished to make them retain their heat.
, Eleventh, the economy of first cost, and in many other ways.consequent on
these improvements, is very great..
Twelfth, the process of rectifying is regulated with unusual accuracy and
ease by an indicator inserted in a tube in the top of the boiler. This indicator
can shew at each moment the precise strength of the acid in the boiler, that
is, how many degrees of the hydrometer the liquor would mark if it were
then in a cool state. The indicator acts by the variations of heat at which
each different strength of acid boils. It is a novel application of the spiral
coil of a compound lamina of two metals of unequal expansion by heat. This
instrument is bere arranged in a new and suitable form, and with important
improvements, without which the said spiral (already known) would not. be
applicable to measure correctly, with uniformly similar indications such a
wide range of temperature. It is composed of alloys which do not become
materially strained by their own unequal expansion of..heat, namely, alloys
having not too great a difference of expansion, and having the utmost elas

page_text: ticity and power of retaining this as much as possible at high temperatures, so
..as to prevent their inequality of expansiveness from giving a permanent set to
their substance. For this end also, more than two laminæ are employed as
preferable, united into one, and having successively greater degrees of expan-
.sion. This improved instrument forms also a superior pyrometer for general
purposes.
I will now particularly.describe the vessels and indicating apparatus. My
improved vessels for such chemical purposes as the rectifying of sulphuric acid
to produce vitriol consists of a boiler, shewn in Figure 1, preferably of a stiff
and elastic alloy of platinum with iridium; it has its greatest extension in the
bottom or base, which is the surface to be chiefly, heated, and comparatively
little extension in its sides, or little height in proportion to its diameter. Its
top part is of comparatively thin material, and is carried up as a hemisphere
or as a cone, at such an angle, and so far truncated by a moveable head N as
to give a general outline approaching to that of a hemisphere. The bottom
consists of a narrow circumferential portion A, A, which is horizontal and flat
and rests on a ring B, B, also horizontal and flat, preferably of cast iron; the
chief portion of the bottom is central to this ring, and is hollow or bellies
downwards C, and in section, is preferably an arc of an ellipse less than a
semi-ellipse; it meets the circumferential part at an angle preferably of 45
degrees or less, and the depth of the centre of the bottom, below the level of
the circumference, is only a small fraction of its diameter. To set the vessel
it is placed on the ring B, B, aforesaid, built into the furnace above and
surrounding the fire D. From the outer circumference of this ring or seat
for the vessel rises a short cylindric portion, which is of such a section as to
conduct the heat received by the lower part of the ring, which has a bevilled
or conical surface E, E, facing the fire, so that this heat is transmitted through
the cylindrical part of the ring to the lower part of the sides of the boiler,
which is thus heated more moderately and regularly than the bottom, so that
the parts which are sometimes liable to have no liquor in contact with them
internally will not be liable to injury from an excess of heat. The hot gases
from the furnace in passing forward from the boiler may be. led under the
ordinary leaden evaporating pans, so as to utilize the rest of the heat.
The boiler is. intended to work with a continuous inflow and outflow of
liquid, regulated by a single cock at the inflow.
An important part of my present improvements consists in a collecting
vessel K, or a nest fixed within the boiler, either by direct union to the side or
preferably at the central part, and slung by wires from the sides, or fastened
by legs extending to the bottom, and pinned to lugs soldered to the bottom

page_text: (one of which is seen at M) in any convenient way that will admit of its
removal for cleaning or repairs. This collecting vessel is fixed with its rim,
which should be of considerable lineal extent, horizontal, at such a level as to
receive the overflow of the liquid, and prevent its boiling up into the head of
the boiler. The liquid which thus collects by overflow into this vessel is made
to overflow pari passu from it for use either through an ordinary syphon
dipping into it and passing through the top of the boiler in the way usually
hitherto adopted for withdrawing liquor from a boiler without any collecting
vessel, or better by a pipe L leading from the side of the collecting vessel K
to: a short pipe G, passing through the side of the boiler a little below the level
of the rim of the collecting. vessel K, and slanting downwards into the mouth
of another pipe H, forming a slip joint, and so leading the liquor from the side
of the boiler into the lower part of a suitable receptácle not shewn in the
Drawing; this receptacle is preferably deep and cylindric, of the same material
as the boiler, and stands in a vessel supplied with a continual change of water.
for cooling. This cooler or receptacle for vitriol has its outflow by a pipe
connected from the bottom, or by a syphon extending from the bottom, and in
either case delivering the liquid at nearly the level of the top of the cooler.
The boiler is supplied with liquid, preferably by a funnel F, trapped by
extending into the liquor below. But to return to the collecting vessel K, its
sides are preferably of a sectional form shewn in the Drawings, and known in
mathematics as the curve of sines. The pipe Ļ from it, which leads into the
outflow pipe G, is united to the side of the collecting vessel K, at so low a
level as to be below the surface of the liquid in K when it is overflowing
through this pipe L, so that gas or vapor cannot escape through it, and a small
arc of, the under side of the pipe L is flattened where it lies in the outflow.
pipe G, so as to allow of liquor passing in small quantity direct from the
interior of the boiler through the under side of the outflow pipe G.
The dimensions of pipes and other parts, as shewn in the Drawing, are.
suitable for three such boilers to be used in series, fixed at levels successively.
lower, over three furnaces built in a row. The outflow of each boiler is carried
into the funnel of the next boiler below by a pipe like that shewn for the final
outflow, only having its parts of suitable length horizontally and perpendicularly..
The surfaces of the boiler which are to receive heat are made rough or "dead"
externally, that is, not polished, and are blackened by attaching, preferably,
finely divided platinum by electric deposition.
My improvements in the apparatus for indicating the degree of concen-
tration of the liquid according to its temperature of ebullition consists in using
an instrument which I call an indicator, Figure 2, inserted through a hole

page_text: in the upper part of the boiler; there are preferably three such holes at equal
distances around it, one for the inflow funnel, one for the indicator, and one for
a float or syphon, or any other occasional purpose. The indicator consists essen-
tially of a helix, which is already known, and.consists of two laminæ of metals,
which expand differently by. heat; the laminæ being united face to face, and
coiled into a helix in such a manner that it partly twists and untwists according
to the changes of temperature:
I improve the form and construction for this instrument, as herein-after
described, to adapt it for use in the boiler, and to make its indications for all
purposes more accurate, and to prevent the zero point from altering so much
as it is otherwise liable to do by a great, variation of temperature. I make
the laminæ of alloys, such as have not much difference of expansion by heat.
The greater the difference of temperature to which it is to be exposed, the less
should be the difference, of expansibility of the laminæ, and the alloys are
such as have as. great a range of elasticity as may be, and retain their
elasticity as well as may be at high temperatures. With these objects I use,
for example, an alloy of, one, part of platinum, with about 8 of gold, for one
lamina, and an alloy of platinum, with:a, small proportion of iridium, for the
other lamina, in such proportion that it shall extend under the rollers equally
with the gold limina when they are, united and are being rolled to the proper.
thickness. I prefer that the two united laminæ shall be equal in width and
thickness.
"
.. A further improvement which I make in the application of this principle of
difference of expansion, is to use a helix composed, not of two lamina only,
but of several, each being of a different alloy, having the properties already
named,, and being of successively different degrees of expansibility by beat
in the order in which they are united; for instance, to the platino-iridium and
auro-platinum laminæ, above described, I add an argento-cuprum lamina,
made of silver and copper in such proportions as to make rather less difference
between its rate of expansion and that of the auro-platinum lamina than
there is between this last named and the platino-iridium lamina, because the
elasticity, of the argento-cuprum alloy is more diminished by, heat, than that of
the other two. The relative thickness of the lamina: should-be in proportion.
to the relative differences of expansibility by heat between each adjacent pair
of laminæ. In this way the internal straining action of the changes of
temperature is reduced as much as may be needed to prevent its exceeding the
limits of elasticity of the material at the highest temperature to which the
instrument is intended to be exposed, so that its index will return to
the proper position when the temperature is again reduced to the lowest.

page_text: degree required, and at the same time the compound helix of three or more
laminæ admits of greater thickness, and consequent stiffness, being given
to it without diminishing its sensitiveness, nor contravening the condi-
tions above named, which preserve it from being strained by the changes of
temperature.
The helix O, O, formed as above described, is attached at its upper end to
a hollow cylindrical stem P, P, preferably of platinum, having a diaphragm,
with a central hole at X and at Y; the axis of the helix being a continuation
of the axis of the stem, and placed vertically when in use. To the lower end
a light hollow spindle Q is attached; it passes through the axis of the helix and
stem, and carries an index or pointer R fixed across its top end, which rotates
by changes of température of the compound helix, and shews the degree of
temperature and of concentration of liquid (provided it be in a boiling state)
in which it may be immersed. The degrees of both kinds, and other data as
to the composition of the liquid or the proportion of water in it, are marked
in two or more concentric circles on a dial S, S, through the centre of which
the spindle passes, which may be. of platinum or of porcelain, is attached to
the top end of the stem P concentrically to it. The lower end of the spindle
terminates in a point resting in a hollow at the bottom T of a cage made of four
or six wires U, U, and which encloses and protects the spiral, and is attached
to the stem of the instrument. It is preferable to place the instrument in a
case or tube V, V, of glass or platinum, contracted about Z, Z, before being
placed in the boiler, so that it shall receive the heat without being wetted by
the acid, or whatever injurious liquid may be in the boiler.
Having now described the nature of my said Invention, and how the same
is to be performed, I claim as my improvements in vessels for boiling chemical
products,―
First, the means of outflow for the boiling liquor, namely, an open shaped
vessel fixed within the boiler, and having its rim at a level suitable to
receive the foam as it rises from the liquor, so that the foam shall settle
therein, and pass out in a liquid state by a syphon, or through a tube attached
to the vessel, so as to trap the vapor within the boiler while the liquid flows
out through the tube, as herein-before described.
Second, the general construction of the vessel for boiling chemical products
arising from the peculiar combination of parts themselves, formed and
combined as herein-before described and represented at Figure 1 of the
accompanying Drawings.
Third, deadening, frosting, or roughening the heating surface of such vessels
externally, substantially in manner and for the purposes described.

page_text: And I also claim the particular construction of the pyrometic apparatus,
herein-before described and represented at Figure 2 of the accompanying
Drawings.
In witness whereof, I, the said William Petrie, have hereunto set my
hand and seal, this Twentieth day of November, One thousand eight
hundred and sixty-two.
WILLIAM PETRIE. (L.S.).