IMPROVEMENTS IN THE CONSTRUCTION OF A FIREDAMP INDICATOR
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
ARTHUR HILL MAURICE No 2 Guildford Crescent, Cardiff in the County of
Glamorgan Mining and Civil Engineer, do hereby declare the nature of my.
invention for IMPROVEMENTS IN THE CONSTRUCTION OF A FIREDAMP INDICATOR
to be as follows: -
My invention has for its object the manufacture of an apparatus or instrument
by which the presence of firedamp or light carburetted hydrogen gas in the
atmospheres of the air-currents roadways, excavations, and working places in
mines may be detected and the quantity or percentage present may be determined.
For the purpose of my invention I employ a conveniently.sized chamber or
vessel which I term the air-vessel, and which can be closed when required and
made perfectly airtight.-Its form is immaterial, convenience and portability being
chiefly considered.
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It may be made of glass, metal, wood or any other substance out of which an
airtight vessel of the required strength may be constructed. It is made with two
openings in it by which the atmosphere within it can be drawn out and replaced by
the atmosphere to be tested. These openings are made to close airtight.
This airvessel is fitted inside with an aneroid barometer, or a mercury gauge, or
some other suitable kind of pressure gauge which is acted upon only by the
atmosphere within the airvessel of the apparatus, and which can be observed
through a glass inserted for the purpose in the side or top of the airvessel, if the
latter should be made of any opaque substance. This gauge is intended to show
changes in density of the atmosphere within the vessel.
The interior of the airvessel is also fitted with a helix or spiral of fine platinum
wire, or with sheets or rolls of platinum foil, or with spongy (finely divided
metallic) platinum. The two extremities of the platinum are attached to insulated
copper wires which pass through to the outside of the air vessel, and are so arranged
that when their two terminals are connected the one to the positive and the other
to the negative pole of an electric battery the platinum within the air-vessel forms
part of the electrical circuit thus established.
In addition to the airvessel and its fittings as described, I use an electric battery
to ignite or raise to a sufficient heat the platinum in the air-vessel. An ordinary
galvanic battery, or a magneto-electric, or an electro-magnetic machine is suitable
for the purpose, and it is made to form part of the apparatus.
The electric current may be obtained by either chemical or mechanical means.

page_text: To use the instrument the atmosphere to be tested is introduced through one of
the openings into the air-chamber. I do this by exhausting through the second
opening the air in the vessel and allowing at the same time the atmosphere to be
tested to replace it through the other opening. The openings are then closed and
the vessel is made airtight.
The aneroid or gauge is next read off and noted. Connection is then made
between the two extremities of the platinum in the air-vessel and the two poles of
the battery so that the platinum forms part of the circuit, and a current of
electricity being established its passage through the platinum raises the temperature
of the latter to the required degree to induce the combustion of any "firedamp" or
carburetted hydrogen gas that may be in the atmosphere within the vessel.
Metallic platinum when heated to a dull red heat has the property of inducing the
union of the Hydrogen and Carbon of which carburetted hydrogen gas (firedamp)
is composed with the oxygen of the air, or in other words it brings about quiet
combustion of the gas.
•
The result of the combustion of the gas is. an alteration in the density of the
atmosphere remaining in the air-vessel, which alteration is indicated by the aneroid
or gauge within it; and by the extent of this change in density the exact quantity
or percentage of carburetted hydrogen or firedamp which was present may be
calculated.
The current of electricity is passed through the platinum as long as combustion
continues which is shown by the continued change in the density of the air. When
the gauge or aneroid remains stationary it is read off a second time, and the
difference between the first and second readings indicates the amount of vacuum
caused by the combustion of the gas. I make tables which show from. the
difference of the two readings the percentage of firedamp" or carburetted
hydrogen gas which had been present. In these tables allowance is made for
variations in barometric pressure or density of the air at the time and in the
place at which the trial is made.
"
The aneroid or gauge being placed within the airvessel no error can arise in
reading the density of the air in the chamber through its heating & consequent
expansion; the air in the aneroid or gauge being heated in the same degree as the
atmosphere in which it is placed.
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page_text: COMPLETE
DIECIFICATION.
ARTHUR HILL MAURICE (late of 2 Guildford Crescent, Cardiff) now of
2 Debrugh Street, Canton, Cardiff, Glamorganshire, Mining Engineer, I do hereby
declare the nature of my invention for IMPROVEMENTS IN THE CONSTRUCTION OF
FIREDAMP INDICATORS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
My invention has for its object the manufacture of an apparatus or instrument
by which the presence of firedamp or light carburetted hydrogen gas in the
atmosphere of the aircurrents, roadways, excavations and working places in mines
may be detected and the quantity or percentago present may be determined.
For the purpose of my invention I employ a conveniently sized chamber or
vessel which I term the airvessel, and which can be closed when required and made
perfectly airtight.
Its form is immaterial, convenience and portability being chiefly considered. It
may be made of glass, metal, or any other substance out of which an airtight vessel
of the required strength and inflexibility may be constructed. It is made with two
openings in it by which the atmosphere within it can be drawn out and replaced by
the atmosphere to be tested. These openings are made to close airtight.
This airvessel is fitted inside with an aneroid barometer arranged as a gauge, or
a mercury or glycerin syphon gauge, or some other suitable kind of pressure
gauge which is acted upon only by the atmosphere within the airvessel of the
apparatus, and which can be observed through a glass inserted for the purpose in
the side or top of the airvessel if the latter should be made of any opaque substance.
The gauge is intended to show changes in the density of the atmosphere within the
airvessel caused by the removal of the gas. The interior of the airvessel is also
fitted with a fine platinum wire or with thin sheets or rolls of platinum foil, or with
spongy (finely divided metallic) platinum or other metal having the same reaction
on firedamp; the two extremities of the platinum or metal of similar nature are
attached to insulated conducting wires which pass through the outside of the
airvessel, and are so arranged that when their two terminals are connected the one
with the positive and the other with the negative pole of an electric battery the
platinum or other similar metal within the airvessel forms part of the electrical
circuit thus established.
In addition to the airvessel and its fittings as described I use an electric battery
to ignite or raise to a sufficient heat, being a red heat, the platinum or other metal
in the airvessel. An ordinary galvanic battery, a magneto-electric, or an electro-
magnetic machine is suitable for the purpose, and it is made to form part of the
apparatus. The electric current may be obtained by either chemical or mechanical
means.
To use the instrument the atmosphere to be tested is introduced through one of
the openings into the airchamber. 1 do this by exhausting through the second
opening the air in the vessel and allowing at the same time the atmosphere to be
tested to replace it through the other opening. Both the openings are then closed
and the vessel is made airtight. The gauge is next read off and noted—Connection

page_text: is then made between the two extremities of the platinum in the airvessel and the
two poles of the battery so that the platinum, or other similar metal, forms part of
the circuit, and a current of electricity being established its passage through the
platinum raises the temperature of the latter to the required degree to induce the
combustion of any firedamp or carburetted hydrogen gas that may be in the
atmosphere within the vessel. Metallic platinum when heated to a dull red heat has
the property of inducing the union of the hydrogen and carbon of which carburetted
hydrogen gas (firedamp) is composed with the oxygen of the air, or in other words
it brings about the quiet combustion of the gas when the latter does not exceed six
or seven percent of the whole mixture.
The result of the combustion of the gas is an alteration in the density of the
atmosphere remaining in the airvessel, which alteration is indicated by the gauge
within it, and by the extent of this change in density the exact quantity or
percentage of carburetted hydrogen or firedamp which was present may be
calculated. The current of electricity is passed through the platinum as long as
combustion continues, which is shown by the continued change in the density of
the air as indicated by the movement of the gauge. When the gauge remains
stationary it is read off a second time and the difference between the first and
second readings, being a rise of the fluid, indicates the amount of vacuum caused
by the combustion of the gas.
The differences between the readings of the gauge, are measured by a scale
attached to it. This scale is divided from actual.trials, and the divisions represent
per cents and tenths of a per cent of vacuum in the closed vessel. The gauge
being placed within the airvessel no error can arise in reading the density of the
air in the inside through its heating and consequent expansion, the air within the
sealed limb of the gauge being heated and expanded in the same degree as the
atmosphere in which it is placed.
Now in order that my improvements may be clearly understood and readily
carried into practice I will proceed to illustrate the same by and describe the
drawings hereto annexed.
Fig. 1 is a section of the airtight vessel, Fig. 2. a front view of the instrument
and Fig 3. a similar view with the scale and gauge omitted so that the platinum
wire may be seen. A, A, is a glass cylinder, closed at each end with vulcanite or
glass discs, B, B, cemented or sealed in so as to be impervious to air. This serves
as the airchamber and it is fitted inside with a fine platinum wire C, the ends are
attached to short conducting wires terminating on the outside of the vessel in
battery connections E, E. In the interior of the airchamber is fixed the glass
syphon gauge D, of the form shown in the drawing and partly filled with colored
glycerin, and attached to the small limb of this is a boxwood scale F, so divided
as to read from one tenth of a per cent upwards, the percentages being indicated
in figures on the scale. The divisions of the scale are arrived at by actual trial
and represent percentages (and decimals) of vacuum in the closed airvessel. The
only communication between the outside and the inside of the instrument is by
means of the two tubes G, and H, leading the one to the top and the other to the
bottom of the airchamber. The middle part of these tubes is of rubber and they
can be simultaneously closed and the airvessel made perfectly airtight by screwing.
up the small brass press or clamp K, Fig 1. When the press is open the air in the
airchamber may readily be exhausted by inhalation through the mouthpiece L,
connected to the end of the tube H, when the air it is intended to test enters
through the other tube G, and fills the vessel. The glass cylinder is almost entirely
enclosed in a light wood case for protection, the battery connections, the screw for
opening and closing the press K, Fig. 1, and the mouthpiece L, only appearing on
the outside. The gauge is read through an opening in the front of the wood
case.
In practice the mode of proceedure is as follows:-
The indicator is taken into the part of the mine where the air is to be tested, and
by means of half a dozen full inhalations through the suction tube the airchamber.

page_text: Is entirely filled with it. The press or clamp is then screwed down and the
instrument is closed. If the battery is carried with the indicator the gauge is now
read and noted; if the battery has been left behind in the "intake" airway or
elsewhere the indicator after being closed is taken to it, and when the gauge
appears stationary it is read and noted. The battery is now brought into action to
such an extent that the platinum wire, which is observed through a small opening
in the case made for the purpose, becomes of a red heat at which point it must be
kept till the firedamp is all consumed.. From trials this is found to occupy five
minutes at the end of which time the battery power may be taken off. A. period of
at least two minutes must now be allowed to elapse to give time for the fluid in the
gauge to recover its normal position, which has been disturbed by the clectrical
current, and it is then read and noted a second time. The first figures are then
deducted from the second and any difference (being a rise of the fluid) indicates the
quantity of gas present in percents and tenths of a per cent. For instance assuming
the first reading to be 3.3%, and the second 45°/ the difference between the two
is 12%, which is the percentage of gas present.
With regard to battery power one large bichromate element which may be
contained in a case 4" x 3" x 7" deep is quite suitable for an airvessel containing
ten cubic inches, the platinum wire being of an inch long and gauge No. 35.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
The improved method of detecting the quantity or percentage of carburetted
hydrogen gas present by enclosing the mixture in an airtight vessel, burning out
the carburetted hydrogen gas only in the manner explained and then measuring
the change of density in the enclosed atmosphere, or in other words the partial
vacuum formed by the destruction of the gas, by means of a suitable gauge,
Bubstantially in the manner herein before described.