Improvements in Photometric Apparatus.
Year: 1889

page_text: Date of Application, 23rd Mar., 1889
Complete Specification Left, 23rd Dec., 1889-Accepted, 25th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Photometric Apparatus.
I JOHN METHVEN of the Gas Light and Coke Company's Works, Nine Elms in
the County of Surrey, Associate Member Institute of Civil Engineers, do hereby
declare the nature of this invention to be as follows:-
My invention relates to that class of photometric apparatus which are known as
jet photometers, the object of the invention being to render these apparatus more
accurate and reliable than heretofore.
It is a well known and accepted fact, that jet photometers, as at present constructed,
are not to be relied upon to give an accurate indication of the quality of the gas to
be tested, and the reason for this is, that not only the apparatus, but the gas itself,
aro more or less seriously affected by changes in the condition of the atmosphere,
both as regards variations in temperature, and in the barometrical pressure.
It will be evident, then, that to obtain perfect accuracy in indicating the
illuminating power of the gas, two conditions are necessary, viz.: a constant
temperature and a constant barometrical pressure.
Now, my invention consists in the means whereby these two conditions are
practically provided for.
In carrying out my invention, I make use of the ordinary jet photometers,
whether they are constructed to indicate the quality of the gas used by maintaining
a constant height of flame, and observing the pressure required to produce that
height of flame; whether they are of a construction to indicate the quality of the gas
used by maintaining a constant pressure, and observing the height of the flame
produced by such constant pressure; or of any other form or description of jet
photometer, where a jet flame is used for the purpose of a photometer.
For the purpose of maintaining an uniform temperature of and within the
apparatus, I enclose in a water jacket the whole of the gas way, and the tank or
vessel containing the water used for indicating the pressure of the gas within the
instrument, and which is commonly known as a King's Gauge. The water within
the jacket I keep at a constant temperature by means of circulating tubes attached to
the water jacket, and heated by a jet or jets of gas. These tubes project
through the box in which the instruments are generally placed for the protection
from draughts, and the heating jets may be brought into contact with them when
desired.
A thermometer is inserted in the water jacket and in the gas way of the
instrument, so that the temperature can be always ascertained.
In this way, the temperature of the gas in the gas ways, or measuring parts of the
apparatus, can always be maintained constant.
A thermometer will also be placed in the box, so that the general temperature in
the box may be the same as the water jacket.
Alterations in the barometrical pressure of the atmosphere affect not only the
volume of the gas in the measuring chamber of the instrument, but also the
combustion of the jet flame.
For instance, with a prevailing high barometer, the volume of gas within the
measuring chamber, or in other words, the volume of gas passing through the
instrument, as indicated by the pressure recorded by the " King's Gauge," is
compressed; consequently, the quantity of combustible material passing through the
jet, to form the flame, is such that a longer flame is required to consume it. The
reverse is the action of a prevailing low barometer. The volume of gas passing
through the instrument, as indicated by the pressure recorded by the gauge, is

page_text: expanded; consequently, the quantity of combustible material which forms the flame
is less, and the flame is of necessity shorter.
The means which I use to provide for changes in the barometrical pressure consist
of a movable scale, by means of which I am enabled to ascertain what should be
the height of the flame according to the barometrical pressure for the time being.
The scale is attached to a frame secured to the top of the instrument just
beneath the socket of the jet burner, and which extends upwards in front of, and
behind the jet flume. The back of the frame is fixed at about two inches from the
centre of the flame, and the front portion at any distance being a multiple of the
distance the back is from the centre of the flame. On the front portion of the frame
is engraved the scale. The centre portion of the front of the frame, which is made
of coloured glass, arranged to be adjusted by a screw arrangement, is moved up or
down the frame in guides provided for the purpose, so that the top edge of the glass
may be brought to the mark on the scale indicating the height of the barometer for
the time being.
The height of the flame will be ascertained in the usual way, by sighting the top
edge of the movable blue glass, the top of the flame, and the line fixed on the
back of the frame. The position of the line on the back of the frame is arrived at
when the instrument is rated by comparison with the results of the standard
photometer. Having adjusted the height of the flame, the readings of the
intrument may be regarded as indicating the correct illuminating power of the gas,
by observing the pressure necessary to give the adjusted length of flame. When the
instruments are designed to indicate the quality of the gas by maintaining a fixed
pressure, and observing the height of the flame produced by such constant or fixed
pressure, the scale indicating the length of the flame may be marked on the
movable blue glass, and which may be adjusted in like manner to the scale indicating
the barometer for the time being; the length of flame will thus have the necessary
correction for the barometer prevailing.
I may also use, to provide for changes in the barometrical pressure, a scale which
I apply outside the ordinary scale on the dial of the instrument, and which
supplemental scale may be worked round the dial by means of a screw which projects
through the side of the box.
The supplemental scales I use, result from observations extending over a long
period of time, and by taking a reading of the barometer, and bringing zero on the
scale to the division at which the pointer of the instrument is arrested, the exact
quality of the gas in candle power can be read off.
Instead of moving the scale, I may secure it on the dial, with zero point on the
scale corresponding to zero on the dial. Then, taking the reading of the barometer,
I make the corresponding reading on the scale zero for the time being, and adjust
the quantity of float water in the instrument to bring the pointer opposite such
division. In this manner, I start with the proper correction according to
circumstances.
In these last named means for providing for variations in barometrical pressure, in
which the scale is used as a supplemental scale to the dial of the instrument, or is
attached to the zero end of the dial, the results obtained are equivalent to those
obtained by altering the height of the flame, but in the latter case the correction
is made on the pressure indicated by the pointer of the "King's Gauge."
.Dated, this 23rd day of March 1889.

page_text: Improvements in Photometric Apparatus.
I JOHN METHVEN of the Gas Light and Coke Company's Works, Nine Elms
in the County of Surrey, Associate Member Institute of Civil Engineers, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
My invention relates to that class of photometric apparatus known as jet photo-
meters, the object of the invention being to render these apparatus 'more accurate
and reliable than heretofore.
It is a well known and accepted fact, that jet photometers, as at present
constructed, are not to be relied upon to give an accurate indication of the quality of
the gas to be tested, the reason being that the apparatus, which is of a delicate
nature, as well as the gas, are both more or less seriously affected by variations in the
condition of the atmosphere, both as regards the temperature and the barometrical
pressure.
It will be evident, then, that to obtain perfect accuracy in indicating the
illuminating power of the gas, two conditions are necessary, viz., a constant
temperature and a constant barometrical pressure.
Now my invention consists in the ineans whereby these two conditions are
practically provided for.
In carrying out my invention, I make use of ordinary jet photometers, such as
are employed to indicate the quality of the gas by maintaining a constant height of
flame, and observing the pressure required to produce such flame, or by maintaining
a constant pressure, and observing the height of the flame produced by such
constant pressure, or any other form or description of jet photometer.
For the purpose of maintaining a uniform temperature of and within the apparatus,
I surround the tank or vessel containing the water used for indicating the pressure
of the gas within the instrument, and known as a King's Gauge, and all the ĝas
ways, with a liquid jacket, which is kept at a constant temperature by means of
circulating tubes heated by a jet or jets of gas.
A thermometer is connected with the jacket, so that the temperature can be
always ascertained, and a second thermometer will be placed in the box in which the
instrument is enclosed (for protection from draughts), so that the general temperature
in the box may be kept the same as the jacket.
Alterations in the barometrical pressure of the atmosphere affect not only the
volume of the gas in the measuring chamber of the instrument, but also the combus-
tion of the jet flame.
For instance, with a prevailing high barometer, the volume of gas within the
measuring chamber, or in other words, the volume of gas passing through the
instrument, as indicated by the pressure recorded by the King's gauge, is compressed;
consequently the quantity of combustible material passing through the jet, to form
the flame, is such, that a longer flame is required to consume it. The reverse is the
action of a prevailing low barometer. The volume of gas passing through the
instrument, as indicated by the pressure recorded by the gauge, is expanded;
consequently the quantity of combustible material which forms the fame is less, and
the flame is of necessity shorter.
To provide for changes in the barometrical pressure, I employ a special scale, by
means of which I am enabled to correct the readings of the instrument according
to the barometrical pressure for the time being.
In the accompanying drawings,
Fig. 1 is a front elevation, partly broken away, of a jet photometer with my inven-
tion applied thereto.
IN
ค
J
1.
1: L
11 L
1.

page_text: The general construction of the instrument is so well known, that it will be
unnecessary for me to describe it. The King's Gauge, and the gas-way leading to
the jet burner, are enclosed in a sealed casing A A¹, to be filled with liquid, which
forms a liquid jacket.
This casing has a circulating pipe B provided with suitable cocks, and which may
be heated by a jet or jets of gas (not shown), as required, to keep the temperature of
the liquid jacket constant. A reservoir C is provided in connection with the
part A of the casing, so that the liquid jacket may be maintained at a constant
level. D is a thermometer, the bulb of which is in the liquid in the casing. E is
the box in which the instrument is enclosed, to shield it from draughts, and in this
box another thermometer is placed, so that the temperature in the box E, and of the
liquid jacket, which must be always the same, may be readily compared. F is the gas
jet burner.
G is a frame secured to the top of the pari A¹, just below the socket of the jet
burner F, and this frame extends upwards both in front of and behind the jet flame.
The back of the frame is fixed two inches from the centre of the flame, and the
front portion will be six and a half inches from the centre of the flame. On the front
portion of the frame G, is engraved a scale H, and the centre portion H' of the
front (made of coloured glass) may be arranged to be moved up or down in guides
provided for the purpose, by means of a screw adjustment H².
The scale for an instrument having a frame G of the proportions above given,
and shown with reference to Figs. 2 and 3, will be divided into inches and tenths
of an inch, to agree with the scale as ordinarily used on a barometer.
To ascertain the value of the gas supplied to the instrument, the movable blue glass
must be placed in such a position that the top edge of the glass shall exactly coincide
with the mark on the scale corresponding to the height of the barometer for the
time being. The height of the flame must then be adjusted so that the top of the
flame, when sighted between the fixed mark on the back of the scale frame, and
the top edge of the blue glass, shall be in line. The indications of the pointer
on the dial (Fig. 1) will then represent the corrected quality of the gas used.
In jet photometers which are constructed for indicating the quality of the gas by
using a fixed or constant pressure, and observing the length of flame produced by
such constant pressure, a scale of inches and tenths is marked on the back of the
frame G, and also on the blue glass. A zero point will be marked on the blue glass,
which point will be moved to a position in line with the barometer indication for the
time being on the scale attached, as above explained, to the front of the frame. The
reading on the blue glass (with the top of the flame, the scale on the back of the box,
and that on the movable blue glass, in line) will represent the quality of the gas
corrected for barometer. The position of the line on the back of the frame, and
the zero point on the several scales, vary in each instrument, and can only be arrived
at when the instrument is rated by comparison with the results of the standard
photometer at the pressure of the atmosphere for the time being. Having adjusted
the height of the flame, the readings of the instrument may be regarded as indicating
the correct illuminating power of the gas, by observing the pressure necessary to give
the adjusted length of flame.
I
may also use,
to provide for changes in the barometrical pressure, a supplemental
scale J, which I apply outside the ordinary scale on the dial K of the instrument,
which supplemental scale may be worked round the dial by means of a worm Jon
the end of a rod projecting through the side of the box E, and gearing with teeth on
the scale, as shown at Fig. 4, or in any other convenient manner.
In this case, the pointer, at starting, must occupy the zero point on the dial. The
length of the flame must then be adjusted in the usual way to the usual height, and
the zero point on the scale J brought under the pointer in the new position it
will have assumed. The corrected reading of the quality of the gas will then be
indicated by the figure on the scale K on the dial immediately opposite to the
mark on the scale J corresponding to the height of the barometer for the time
being.

page_text: Instead of moving the scale, 1 may secure it to, or make it on the dial with zero
point on the scale corresponding to zero on the dial. Then, taking the reading of the
barometer, I make the corresponding reading on the scale zero for the time being,
and adjust the quantity of float water in the instrument to bring the pointer opposite
such division. In this manner, I start with the proper correction according to
circumstances, the length of flame being the usual seven inches.
In these last-named means for providing for variations in barometrical pressure, in
which the scale is used as a supplemental scale to the dial of the instrument, or is
attached to the zero end of the dial, the results obtained are equivalent to those
obtained by altering the height of the flame, but in the latter case, the correction is
made on the pressure indicated by the pointer of the King's Gauge.
It will be understood that in all cases it is necessary, before adjusting for the
barometrical influence on the flame, to adjust the temperature of the apparatus to the
specified degree.
In setting out the supplemental scales, I describe a circle having a radius equal to
the distance from the centre to a point where the distance between two radial lines
is one inch, and I then draw lines dividing the one inch into tenths. If the radius
of the dial is to be less than that of the circle, the distances between the lines will be
correspondingly less.
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
1st. Ensuring a constant temperature of the gas in the gas ways of jet photometers,
by surrounding said ways with a liquid jacket, the temperature of which may be
regulated as required.
2nd. The means above described for correcting the readings of photometric apparatus
in relation to the barometrical pressure for the time being.
3rd. The improvements in photometric apparatus, as herein shown and described.
Dated this 23rd day of December 1889.
NEWTON & SON,
Agents for the Applicant.