IMPROVEMENTS IN THE DETECTION AND ESTIMATION OF THE QUANTITY OF FIRE-DAMP AND OTHER INFLAMMABLE GASES OR VAPOURS IN THE AIR OF MINES OR OTHER PLACES, AND IN THE INSTRUMENTS OR APPARATUS EMPLOYED THEREFOR."
Year: 1880

page_text: LETTERS PATENT to John Aitken, of Falkirk, in the County of Stirling, North
Britain, Engineer, for an Invention of "IMPROVEMENTS IN THE DETECTION
AND ESTIMATION OF THE QUANTITY OF FIRE-DAMP AND OTHER INFLAMMABLE
GASES OR VAPOURS IN THE AIR OF MINES OR OTHER PLACES, AND IN THE
INSTRUMENTS OR APPARATUS EMPLOYED THEREFOR."
PROVISIONAL SPECIFICATION left by the said John Aitken at the Office.
of the Commissioners of Patents on the 5th March 1880.
JOHN AITKEN, of Falkirk, in the County of Stirling, North Britain, Engineer.
"IMPROVEMENTS IN THE DETECTION AND ESTIMATION OF THE QUANTITY OF FIRE-
DAMP AND OTHER INFLAMMABLE GASES OR VAPOURS IN THE AIR OF MINES OR
OTHER PLACES, AND IN THE INSTRUMENTS OR APPARATUS EMPLOYED THEREFOR."
This Invention, which relates to improvements in detecting fire-damp and other
inflammable gases in mines and other places, consists in the use in certain ways
hereinafter described of catalytic substances, such as platinum in its different forms
and combinations, but I do not confine myself to the use of platinum, but include
all those analogous classes of substances known to chemists as capable of producing
contact or catalytic action, such as palladium, rhodium, iridium, osmium, gold,
silver, cobalt, nickel, charcoal, or carbon, pumice stone, porcelain, glass, rock crystal,
fluor-spar, tow, cotton, rags, and platinized charcoal in their different forms and
combinations. Any catalytic substance may be used alone, or it may be mixed
with some other catalytic substance with a porous substance, or with some neutral
substance; or the catalytic may be deposited in the pores of any substance by any
of the well known chemical processes.
In one form of instrument for carrying out this Invention the catalytic substance,
or the catalytic substance and its mixtures, may be caused to adhere to a thermo-
meter with cement, or platinum black, for instance, may be mixed with plaster of
Paris or other cement, and the bulb of the thermometer covered with the mixture.
The thermometer is so placed that the air to be tested is passed over it, another
thermometer of any construction being placed so as to show the temperature of
the-air or-gas-to-be-tested-before-coming-in-contact with the catalytic substance.

page_text: When the thermometers are so arranged the difference of temperature between the
two indicates the amount of fire-damp or other inflammable gas present in the air
tested. The air to be tested may be allowed to circulate by natural causes, or it
Thermometers of any
may be made to circulate more quickly by artificial means.
construction may be used for this purpose.
In the second form of instrument the air to be tested is passed over or through
the catalytic substance, a thermometer being placed so as to show the temperature
of the air before it arrives at the catalytic substance, and another thermometer to
give its temperature after it has passed through the catalytic. The difference
between the readings of the two thermometers gives the amount of fire-damp
present.
In the third form of instrument the air to be tested is introduced into a confined
space, and made to pass through or over the catalytic substance, when the increased
pressure or the increased volume indicates the amount of fire-damp or other
inflammable gas present; or the air may be kept at a constant temperature, and
the change of volume will then indicate the amount of fire-damp present. Or the
air may be allowed to escape on expanding, and the reduced volume on returning
to the original temperature will indicate the amount of fire damp present.
The fourth form of instrument consists of a diffusion tube or diaphragm, in which
the diffusion tube or diaphragm is made of a catalytic substance, or a mixture of a
catalytic with some other substance, by preference porous. The tube or diaphragm
may be made in whole or in part of the catalytic substance, and the rest of some
porous material, the tube or diaphragm being provided with a suitable index and
scale.
The fifth form of instrument is a diffusion tube or diaphragm provided with a
suitable index and scale, and having a catalytic substance inside it, and by pre-
ference provided with a covering or box, in which it is kept when not in use; or
the box or covering may form an air-tight casing for the tube or diaphragm, and
be used together with the tube or diaphragm in detecting the fire-damp; or an
ordinary diffusion tube or diaphragm may. be used by placing it, before making a
test, in a box containing a catalytic substance.
In working some of these instruments to detect fire-damp and other inflammable
gases it is found preferable to work at a higher temperature than that of the mine.
A temperature of 212° F. is very convenient, as it can easily be maintained con-
stant, which enables the tests to be made more easily and quickly. Any degree
of heat however which may be found convenient may be used. The heat may be
supplied in any ordinary manner, such as by lamps, fires, steam, or electricity; or
the fire damp in the mine may be made to supply the necessary heat by means of
a catalytic substance. These instruments may also be used at the ordinary
temperature of the mine or other place tested.
In order to further facilitate the working of these instruments it is found in
many cases to be advantageous to operate with intermittent currents of the air or
gas to be tested, or at least with intermittent action of the catalytic substance.
This method of working is found to be advantageous when operating at low
temperatures and with small amounts of fire-damp in the air.
The instruments described are best suited for use when making a personal
inspection of the mine. They however may be made with certain additions, so
that when placed in the mine or any other place they will give warning all over
the mine, at the office, the pit head, or other places desired when the air, where
the instrument is placed, is in an unsafe condition; or they may be made to
indicate at any place desired the condition of the air at the point where they are
fixed. This is effected by placing the instrument in electric communication with
the points at which the warning is desired to be delivered, and the instrument, by
sending an electric current or currents, may sound an alarm or telegraph the con-
dition of the air in the mine or other place where the instrument is placed. This
may be accomplished by means of the expansion of the thermometer making

page_text: electric contact when the amount of gas exceeds a certain proportion; or the
instruments may be made to telegraph their condition by any of the well known
methods used for such purposes. Any kind of thermometer may be used for this
Invention, but metal rods seem most suitable. The diffusion tubes may also be
made to give warnings by electricity.
Another form of instrument for telegraphing the condition of the air is a thermo-
pile or battery, one face of which is covered with a catalytic substance, and the
pile put in electric communication with a galvanometer, the readings of which will
indicate the amount of fire-damp present.
The use of these instruments is not confined to the detection of fire-damp, but
they may be used for the detection and estimation of any inflammable gas or
vapour, such as the unconsumed gases in furnace flues and the like.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Aitken in the Great Seal Patent Office on the 3rd September
1880.
JOHN AITKEN, of Falkirk, in the County of Stirling, North Britain, Engineer.
"IMPROVEMENTS IN THE DETECTION AND ESTIMATION OF THE QUANTITY OF
FIRE-DAMP AND OTHER INFLAMMABLE GASES OR VAPOURS IN THE AIR OF
MINES OR OTHER PLACES, AND IN THE INSTRUMENTS OR APPARATUS EMPLOYED
THEREFOR."
The said Invention consists in the employment in certain ways, as hereinafter
described, of catalytic substances, such as platinum, or other substances capable of
producing the combustion or decomposition of inflammable gases by catalytic action,
so that by the contact of the air to be tested with the catalytic substances such
change in the temperature or volume of the air or gas being tested is produced as
to enable an indication to be obtained of the amount of fire damp or other inflam-
mable gas present in such air.
In order that my said Invention may be properly understood I now proceed to
set forth the system, mode, or manner in or under which the same may be used or
carried into practical effect, reference being had to the accompanying Drawings and
to the letters and figures marked thereon, that is to say,-
Figure 1 illustrates one form of apparatus for carrying my Invention into effect.
a and b are two thermometers, which may be of the usual construction, but any
form of thermometer may be used. The thermometer b has its bulb covered with
a coating 63 of some catalytic substance, such as a mixture of platinum black and
plaster of Paris. The bulbs of the two thermometers are enclosed in the chamber c,
and the air to be tested is passed into this chamber, so that it comes into contact
first with the bulb of the thermometer a, and then passes to the bulb of the
thermometer b. If there be no inflammable gas in the air the two thermometers
will indicate the same temperatures, but if any inflammable gas be present in the
air the two thermometers will not indicate like temperatures, but the upper one b
will indicate a higher temperature than that indicated by the thermometer a, and
the more inflammable gas there is present in the air the greater will be the difference
between the readings of the two thermometers a and b. It is sometimes preferable
to heat the gases before testing them, as it makes the action of the instrument more
certain. The chamber c is shewn provided with arrangements for thus heating the
air; d is a boiler, the upper part of which surrounds the chamber c, the lower part
being provided with the pipes e, e, for heating the gases to be tested. The boiler
is kept hot by means of the lamp f, which is supplied with air by the openings at i.
The Hame of the lamp facts upon the bottom of the boiler, and the hot gases from
the said flame pass up the space k between the outer casing 7 and the boiler d, and
escape at the openings m. The openings and m are covered with wire gauze or
other protection to prevent the danger of explosion. The air to be tested enters
by the inlet g into the chamber h, from which it passes up the tubes e where it is
heated. Its temperature is taken first by the thermometer a, from which it passes
to the thermometer b, and comes into contact with the catalytic substance 62, and, as
already stated, the difference between the indications of the said thermometers a and b
gives the amount of inflammable gas present in the air tested. The air may either
be allowed to circulate naturally through the apparatus by means of its less specific
gravity, which may be assisted by means of the draught tube n, or it may be
caused to circulate by artificial means, such as bellows or pumps, or the like. The
opening g should be provided with a valve to stop the current of air when desired,
as this will enable the presence of very small quantities of inflammable gas to be

page_text: indicated with greater certainty. Any other suitable arrangement may be
employed for heating the air, and any suitable temperature used, but that herein-
before described and illustrated is particularly suitable as a constant temperature
is thereby maintained, whereby the testing is more satisfactorily accomplished.
Another form of apparatus for carrying my Invention into effect is illustrated in
Figure 2. The air to be tested enters the tube c and passes over the bulb of the
thermometer a, then enters the box D, in which is placed some catalytic substance,
such, for example, as platinized charcoal. The air in its passage through the
catalytic substance has its inflammable gas burned and its temperature raised. The
air then passes around the bulb of the thermometer b, and finally escapes at e.
The difference between the readings of the thermometers a and b will then shew
the amount of inflammable gas present in the air tested. An arrangement for
heating the air being tested similar to that hereinbefore described may be advan-
tageously used with this instrument. The thermometers of the instruments shown
in Figures 1 and 2 may be graduated either for temperatures or for per centages
of gas.
In the third form of instrument for carrying my Invention into effect the air to
be tested is kept in a confined space, in which it is acted upon by the catalytic
substance and the amount of inflammable gas present is indicated by the change
which then takes place. Figures 3 and 4 illustrate two arrangements of apparatus
or instruments constructed upon this principle, in both of which the air or gas to
be tested is kept in a confined space, and at as near as possible a constant
temperature. In the arrangement, Figure 3, a cylinder a is fitted with a piston b
and plunger c, the said piston and plunger being made in one or connected
together. A cock or valve d communicates with the cylinder a above the piston b,
and cock or valve e communicates with the cylinder a below the piston b.
A pipe communicates between the spaces of the cylinder above and below the
piston b, the said pipe being provided with a cock or valve g. A pressure gauge h
is provided communicating with the cylinder a. The lower part of the inside of
the cylinder a is either wholly or in part covered with a catalytic substance. In
operating with this apparatus the piston b is drawn to the top of the cylinder a,
the valve g is closed, and the valves d and e opened. The piston is now caused to
descend to the bottom of the cylinder. By this operation the air to be tested is
drawn into the cylinder a above the piston b. After the temperature above and
below the piston has become equalized the valves d and e are closed, and the
valve g opened, and the piston drawn to the top of the cylinder a. The air to be
tested is thus caused to pass from above the piston b through the pipe f to below
the said piston and there to come into contact with the catalytic lining of the
inside of the cylinder. After the inflammable gas has been burned by this contact
and its temperature reduced by contact with the sides of the cylinder its reduced
volume is indicated by the pressure gauge h. The greater the amount of
inflammable gas in the air the greater the reduction in the pressure, and
consequently the higher, will the fluid in the gauge rise. In working with this
instrument it is generally preferable to work at a higher temperature than that of
the surrounding air. This instrument (Figure 3) with some slight modifications
may be used in a different way. If instead of or in addition to surrounding the
inside of the cylinder with the catalytic substance the air in its passage from the
top to the bottom of the cylinder be made to pass through a box filled with a
catalytic substance, so that the inflammable gas may be burned as quickly as
possible and all kept at a high temperature, then the increased volume, as shewn
by the pressure gauge when the gas is passed from the upper to the lower side of
the piston, gives an indication of the amount of gas present.
With the arrangement of apparatus shewn in Figure 4 a much higher temperature
may be used than is possible with the arrangement shown in Figure 3. In the said
Figure 4, a, a, are two vessels of equal volume connected by means of the

page_text: tubes b, b¹, and U shaped pressure gauge tube c. The said tube c is partly filled
with a liquid to indicate difference of pressure inside the two vessels a, a¹. f, f', are
two fine wires inside the two vessels a, a¹. These wires are connected with a
battery by means of wires e, e, e¹, e¹, so that an electrical current may be caused to
circulate through and heat the wires f. ft. The electric current may be made to
circulate through each wire in succession, or it may be caused to divide, one half
going to heat each wire. Any source of electricity may be used to heat the
wires ff, such as galvanic batteries, thermo-piles, or magneto-electric machines.
The wires ff may be made of platinum or palladium, or the wires may be simply
used as a source of heat to raise the temperature of any catalytic substance placed
on them. For instance, platinum wire may be covered with palladium black, or it
may be covered with palladium wire or foil, or the platinum wire may be covered
with a coating of palladium or other catalytic or other substance which will cause
the particular inflammable gas tested for to combine with the oxygen in the air.
The tubes b, b', communicate at h, h', with the air, but are closed when desired by
The two wires f, f', and their
valves or screw plugs as at h³, or by other means.
currents are so adjusted as to give equal heating effects. In operating with this
apparatus air is first put in the vessels a, a¹. The openings at h² are then closed
and the current of electricity passed through the wires f and f¹ when, as both wires
produce the same heating effect, the pressure inside the vessel a is the same as
inside that a¹, as shewn by the liquid standing at the same level in both legs of the
tube c.
The instrument is then in working order. When any air is to be tested it
is introduced into either one or other of the vessels a or a¹, which may be done
by passing a small pipe down the pipe b (or b¹) and passing the air to be tested
through this pipe to the inside of the vessel (a or a¹), the air in the said vessel a
(or a¹) escaping by the pipe b (or b³), or a separate pipe may be introduced for this
purpose, or the air in the vessel (a or a¹) may be displaced by a liquid, and the gas
After the air to be
or air to be tested allowed to enter as the liquid flows out.
tested has been introduced the openings at h³ which were both open are then closed
and the liquid in the tube c is still standing at equal levels in both legs. The electric
current is now turned on, the wires f, f¹, heated, and the inflammable gas in a
(or a¹) burned, and the altered volume is now shown by the change of level of the
liquid in the U tube c; the quicker and greater the change of level the greater the
amount of inflammable gas present. The scale attached to the U tube may be
graduated to shew per centages of gas present.
The fourth form of instrument for carrying my Invention into effect consists of
a diffusion tube, or of a diaphragm, made of a catalytic and some porous substance,
such as a mixture of platinum black and plaster of Paris; or the tube or diaphragm
may be simply lined with this mixture, or the mixture may be covered on both
sides with a porous substance. The tube or diaphragm is provided with an index
and scale.
The fifth form of instrument is an ordinary diffusion tube or diaphragm provided
with an index and scale, and having some catalytic substance inside it and kept in a
box when not in use; or the catalytic may be kept in the box in which the tube
is kept, the object being to burn off all gas inside the tube and make and keep
it ready for use.
To telegraph warning of an unsafe condition of the air at the place where the
instrument is placed an ordinary mercurial thermometer, the bulb of which is
covered with a catalytic substance, may be used, by causing the mercury when it
rises to a certain temperature to make electric communication in any of the usual
and suitable ways for effecting such communication with the points at which it is
desired to send the warning. Figure 5 shows a way of accomplishing this. a is a
metal rod covered with the catalytic substance and contained in a chamber x, to
which the air and gases have admittance; the upper end of the said rod rests
against the spring b, which carries a platinum point 62 at one end, and is fixed at

page_text: the other end which is in electric communication with a galvanic battery. When
the rod a becomes heated by the combustion of the gas in the air being tested by
contact with the catalytic substance the said rod a expands and brings the platinum
point b at the end of the said spring b in contact with the stud c, which is in electric
communication with the other pole of the battery; when contact is made the
current flows, and any alarm instrument placed in the circuit is put in action.
my
Figure 6 illustrates an instrument constructed according to Invention for
telegraphing to any desired point or points the condition of the air at the place
where the instrument is situated. a is a thermo-pile of the usual construction;
one face of this pile is covered with the catalytic substance. The pile is put in
electrical communication with a galvanometer b. The heat generated by the com-
bustion of the gas at the pile causes a current to flow to the galvanometer, which
is thereby deflected from its position of rest, and the greater the amount of gas
present the greater is the deflection of the galvanometer on account of the greater
heat giving rise to a stronger current.
The use of the herein before described instruments is not confined to the detection
and estimation of any one particular gas or vapour, but may be employed for the
detection and estimation of any inflammable gas or vapour, such as the coal gas
used for lighting and heating houses, the unconsumed gases in furnace flues, aud
the like.
Having now described and particularly ascertained the nature of my said
Invention, and the system, mode, or manner in or under which the same is or
may be used or practically carried into effect, I would observe in conclusion that
what I consider to be novel and original, and therefore claim as the Invention
secured to me by the hereinbefore in part recited Letters Patent is,―
First. The apparatus for indicating the presence and quantity of inflammable
gases or vapours in the air of the place tested, the said apparatus consisting in the
combination of two thermometers, one of which is placed so as to give the tem-
perature of the air and gases before they have come into contact with catalytic
substances, and the other of which is placed so as to give the temperature of the
said air and gases, or of the catalytic substance after the said air and gases have
come into such contact, whether such apparatus be combined or not with means for
artificially heating the said air and gases, all essentially as hereinbefore described
with reference to Figures 1 and 2 of the accompanying Drawings.
Second. The apparatus, constructed or arranged essentially as hereinbefore
described with reference to Figures 3 and 4 of the accompanying Drawings, for,
indicating the presence and quantity of fire-damp or other inflammable gases or
vapours in the air of coal mines or other places by the differences of pressure
exerted upon a column of liquid or other pressure gauge before and after the
decomposition or ignition of the said gases or vapours.
Third. A diffusion tube or diaphragm made of or operated with a catalytic
substance as constituting an instrument for detecting the presence of inflammable
gases or vapours, as herein before described under the fourth and fifth beads of my
Invention.
Fourth. The means or apparatus described with reference to Figure 5 of the
accompanying Drawings for indicating at some distant place the presence of a
dangerous amount of inflammable gases or vapours in the air where the instrument
is placed, wherein the increase of temperature caused by the contact of the said
gases or vapours with a catalytic substance is made to complete the circuit of an
electric current and sound an alarm.
Fifth. The means or apparatus described with reference to Figure 6 of the
accompanying Drawings for indicating the presence and estimating the quantity of
inflammable gases or vapours in the air where the instrument is placed, consisting
in the combination of a thermo-pile and catalytic substance with a galvanometer,
so that the degree of temperature which is generated by the contact of the said

page_text: gases with said catalytic substance causes a more or less powerful electric current
to pass to the said galvanometer according to the quantity of inflammable gases or
vapours present, whereby an estimation of the quantity of such gases or vapours is
obtained from the indications of the galvanometer.
In witness whereof, I, the said John Aitken, have hereunto set my hand 5
and seal, this First day of September, in the year of our Lord One thousand
eight hundred and eighty:
JOHN AITKEN. (L.S.)