Improvements in and relating to Processes and Apparatus for Analyzing Gases and Gaseous Mixtures.
Year: 1894

page_text: Date of Application, 7th May, 1894-Accepted, 10th Nov., 1894
COMPLETE SPECIFICATION.
Improvements in and relating to Processes and Apparatus for
Analyzing Gases and Gaseous Mixtures.
We, EDWARD A. UEHLING, Mechanical Engineer, and ALFRED STEINBART,
Metallurgical Engineer, both residing at 1110 North 24th Street, Birmingham, in
the County of Jefferson, and State of Alabama, United States of America, 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:-
Our invention has for its object the continuous and automatic determination of
the percentage of various gases in a gas mixture, in such manner that the actual
composition of the gas mixture may be observed at all times and read off as often
as necessary.
So far as we are aware, and can determine, the various components of a gas
mixture have never before been automatically and continuously analyzed during
the production of the gas. Although our invention is applicable to the analysis of
gas mixtures derived from any source, from which quantities of the same may be
taken, yet the main object is to effect the quantitative analysis of a gas mixture
during its production with a view to facilitating the production of gases of any
desired composition. The methods heretofore resorted to in analyzing gases are
extremely tedious and expensive, and are carried out as follows.
A sample of gas is taken from the source of its production and conveyed in a
suitable vessel to the laboratory where a small portion is measured off with great
care by means of a graduated tube, and is then transferred to an absorption pipe, in
which one of the components of the gas is absorbed by a suitable reagent the
remaining gas is again returned into the graduated pipe, the quantitative loss
determined and known. The remaining gas is transferred into a second absorption
pipe and exposed to a second reagent whereby a second portion or component of
gas is absorbed, the remaining gas being reconducted to the graduated pipe and the
quantitative loss again determined as before. This operation has to be repeated
for each component of the gas mixture, and from the quantitative losses after each
absorption the components of the mixture must be determined. This method
although the best of all those now known is extremely tedious and can only be
carried out by one skilled in the art. The process is very expensive, and requires
such a length of time that for practical purposes the method is practically useless,
in that the analysis can only determine the percentage of components of a gas
mixture at the time of the taking of the sample.
For these reasons gases are seldom analyzed as often as would be necessary for
the controlling of the manufacture of a definite gas mixture, and even not then
where a knowledge of the composition of a gas mixture is of great importance or
value. Such a control would for instance be very important to the manufacture of
illuminating gas, and generator gases used in the smelting of steel and other
metallurgical processes.
Our invention is designed to obviate all these difficulties.
An apparatus constructed according to our invention can be applied to a gas
conduit from which it continuously takes a small quantity of the gas mixture and
continually analyzes the same, so that the composition of the mixture can at all
times be read off from a suitable scale. In this manner, without manipulation and
expense other than that of the reagents any abnormal composition of the gas
mixture is at once visible, so that a change in said composition is rendered possible,
which is valuable to the manufacturer as well as to the consumer. Our invention

page_text: may, for instance be used for the purpose of watching the composition of the gases
from blast furnaces.
A knowledge of this composition is of great utility for the determination of any
irregularity in the smelting process which if not remedied, will often lead to serious
difficulties. Furthermore, our invention may be used for controlling heating plants
of any kind in view of the fact that an analysis of the smoke will show at all times
the percentage of carbon di-oxid or monoxid, thereby indicating the more or less
perfect combustion of the fuel, and whether the greatest heating power has been
attained. In order that the operations above stated may be carried out, and the
results obtained, our invention consists in a novel method of operation, and novel
parts and combination of parts hereinafter described and shown in the form of an
apparatus in the accompanying drawings. It is, however, expressly stated that the
apparatus herein shown is simply for the purpose of illustrating one form of our
invention, and that our invention may be carried out by apparatus of various other
forms.
Referring to these drawings:
Figure 1 represents in sectional elevation an apparatus in its complete organization
embracing our invention.
Figure 2 is a detail view illustrating the principle of our invention; and
Figure 3 is a graphical development of an index used to read off the percentage
of the gas to be determined.
The principle of our invention for the analysis of gases may be stated as follows:
If a tube be divided into three compartments by partitions containing very small
apertures and one of the exterior compartments be filled with gas of a higher
tension than the other and if the tension in both of these compartments remain
constant the following will take place. The gas of the higher tension will flow
towards the compartment of the lower tension passing on its way through the
central compartment in which it will assume a constant tension which we will call
the "normal tension." If now a part of the gas in the central compartment is
continuously taken away, a change of tension will take place in this compartment
which change of tension will depend on the quantity taken away.
Again, if the specific gravity of the gas be changed in the central compartment,
the tension will be also affected and the degree of this change of tension is
dependent on the degree of change of the specific gravity of the gas in the com-
partment. These facts we have utilized in our invention in that we employ the
central compartment as an absorption chamber into which the gas of the first
compartment with constant tension continuously flows and from which it escapes
continuously into the third compartment of lower constant tension. The inlet and
the outlet consist of small apertures; and the absorption chamber is connected
with an instrument for measuring tension. The specific gravity of the gas is
measured either before entering or after leaving the absorption chamber by a
suitable gravity meter.
If a
a component of gas be taken away continuously by absorption by means of a
suitable reagent, which is introduced into the compartment without affecting the
tension, then a change of tension will take place in the absorption tube or chamber
and the quantity of gas corresponding to the change of tension can be read off on
the manometer by suitable indices. The form of these indices depends upon the
specific gravity of the total gas mixture and the specific gravity of the component
absorbed.
These statements are explained and proven as follows: Referring to the
illustration shown in Fig. 2 if two compartments, one of which is filled with a gas
of higher tension and the other with a gas of lower tension be united by a very
small aperture the gas will flow from the compartment of higher tension through
the opening into that of lower tension. The velocity of flow through the opening
depends according to the laws of areomechanics: First, upon the difference of
tension in the two compartments. Second, upon the specific gravity of the gas
of bigher tension. A gas of higher specific gravity flows slower through the

page_text: opening than a gas of lower specific gravity under similar conditions, because a
greater mass has to be set in motion being impelled by equal forces. Now suppose
that the gas to be analyzed be forced through a tube by connecting the one end of
the same with the vessel containing the gas mixture and the other end with a vessel
filled with gas of a lower tension. Let this tube be divided into three compartments
by two partitions which are provided with very small openings; let the central
compartment which we will call "absorption chamber" be connected with a
manometer as shown in Fig. 2. This combination consisting of the two (2) com-
partments A and C, the absorption chamber B, the partitions with the small
apertures a and b and the manometer i connected with B, we will in the following
call absorptionmeters. In the first of these compartments A, in Fig. 2, the gas
mixture has the tension b. (the higher tension) in the third compartment C the gas
has the tension b₂ (the lower tension). Under these conditions the gas will flow
through the aperture a into the absorption chamber B and from there through the
aperture into the compartment C.
If the tension, and b, are constant, that is, if the tension bo remains the same no
matter how much gas flows towards C and the tension b, remains the same
irrespective of the quantity of the gas which flows into it from the compartment A,
then the tension in the absorption chamber B will also become constant; this
tension, the "normal tension" is measured by the manometer connected with
chamber B. As soon as this equilibrium is established, equal weights of gas will
pass through both apertures in the same space of time, because the same gas has to
pass through both openings. The velocity of flow through the respective openings
will also become constant. The velocity through the aperture a depends on the
difference of tension between bo and b₁ (the tension in B), and the velocity through
the aperture depends on the difference of tension between by and by. The specific
gravity of the gas mixture is the same at both apertures, because the gas remains
unchanged and exerts no influence.
The conditions however, become quite changed if in the absorption chamber B
a component of the gas mixture is continually taken away which may take place
by absorption, combustion or condensation, or in any other manner. As soon as
this occurs the tension in B is reduced, in consequence of which the gas will flow
more slowly through the aperture and more rapidly through the aperture a
respectively out of and into the absorption chamber. For this reason the tension
will continue to decrease only until as much gas enters at the aperture a as escapes
at the aperture b, plus the quantity taken away, and then again becomes constant,
but lower than the normal tension.
If no change of specific gravity of the passing gas is caused by the taking away
of the component of the gas, then the tensions in the chamber B will correspond to
the percentages of the gas removed, which tensions we therefore employ to measure
the quantity of gas absorbed by means of a manometer and an index, the "normal
index of the absorption meter."
"
The gas mixtures to be analyzed however may consist of gases of various specific
gravities, for example: Carbon di-oxide in relation to air has the specific gravity
of about one and one half, carbon monoxide about one, hydrogen about 007. That
is carbon dioxide is about one and one half times as heavy as air, hydrogen,
however, is fourteen times lighter. If carbon dioxide is absorbed from a gas
mixture containing eighty per centum of carbon dioxide ten per cent. of air, ten
per cent. of hydrogen, the specific gravity of the total mixture is much greater than
that of the remaining gas mixture which is composed of equal parts of hydrogen
and air. The specific gravity of the former is 1.3 and of the latter only 0.53 in
relation to air; the remaining mixture will therefore pass through the second
aperture easier and quicker than it would if its specific gravity was the same as
that of the total mixture. The consequence of this is, that the tension in the
absorption chamber B will fall more than it would if the specific gravity of the
remaining mixture were the same as that of the total mixture, the eighty per centum
of the carbon dioxide being taken away.

page_text: The change of the specific gravity in the absorption chamber takes place because
the specific gravity of the total mixture is not always the same as that of the gas
total absorbed. The change of the specific gravity of the total mixture causes a
different relation between the specific gravity of the total mixture and the specific
gravity of the remaining mixture with the same percentages of the gas absorbed.
For this reason a change in the specific gravity of the total mixture will cause a
deviation of the tension in the absorptionmeter from that indicated by the "normal
index" for the same percentage of the gas absorbed, so that for every change in
the specific gravity of the total mixture the normal index must be correspondingly
rectified.
The normal index can according to this also be rectified for the specific gravity
of the remaining gas mixture which flows from the absorptionmeter. In order to
determine the exact percentage of the compound of the gas mixture absorbed, we
can therefore either determine the specific gravity of the total gas mixture
or that of the remaining mixture by a suitable instrument for measuring specific
gravities. The rectified index corresponding to the specific gravity so determined
is then applied to the manometer and the per centum of the gas absorbed
read off.
If in practice we wish to determine several components of the gas mixture it is
necessary to employ a corresponding number of absorptionmeters. These may
according to circumstances, be arranged either side by side, or in succession. In
the arrangement side by side a fraction of the gas purified by filtration or other
meaus, passes directly through one of the absorptionmeters, another fraction
through a second absorptionmeter, a third fraction through a third absorptionmeter
and so on.
The arrangement where the absorptionmeters are placed in sucression the
remaining mixture of the first absorptionmeter passes into the second and the
remaining mixture of the second passes into the third absorptionmeter and so on.
An absorption tube may also precede an absorption meter in which a component of
the gas, whose value is not necessary to be determined can be taken away. The
arrangement side by side is the most generally employed. The arrangement in
succession is generally used only in cases where a reagent influences more than one
component of the gas mixture, for instance in the analysis of hydrogen where
carbon monoxide is present. In this case the carbon monoxide must be previously
removed because the combustion of the hydrogen by means of oxygen in the
presence of carbon monoxide would result in water and carbon dioxide, which
would destroy the accurateness of the analysis.
Finally the absorptionmeters may be arranged side by side and in succession in
the same apparatus. In a large number of cases in practice the percentages of a gas
can be determined with sufficient accuracy without measuring the specific gravity,
because the change of the specific gravity of the remaining gas mixture is so small
that it can be neglected. Where the determination of the specific gravity becomes
necessary one apparatus for determining the same will suffice for all absorption-
meters, if the specific gravity of the total mixture is measured by it.
Referring now to the apparatus illustrated in Fig. 1 of the drawings, the
following is a description of a structure for carrying out one form of our
invention.
The
S indicates an instrument for determining the specific gravity of the gas.
D indicates a filter. C1 C2 indicate two absorption chambers. F indicates a
regulator in connection with an aspirator G. 2 and 2 indicate seals.
apparatus is adapted to the analysis of a gas mixture for carbon dioxide and
carbon-monoxide, where the specific gravity of the remaining mixture may vary
between limits, for instance the waste gases of blast furnaces and the producer
gases. The gas which before entering the apparatus is cleaned from dust and
condensible constituents, is continuously furnished from the gas main under slight
pressure. It enters the apparatus through the stop cock a just behind which is
inserted a T-piece through which a portion of the gas flows by the pipe 2 to the

page_text: specific gravity meter S and thence to the atmosphere by the pipe 3.
If the stop-
cock a is only slightly opened the gas after passing it will be under atmospheric
pressure because it is in connection with the atmosphere at 3.
This pressure corresponds to the higher tension 6º. The lower tension by is
created by the aspirator G and kept constant by the connected regulator F. The
regulator consists of an airtight vessel partially filled with water into which the
gas mixture from the absorptionmeters slowly flows. The aspirator G actuated
by water, air or steam, in this case by water, through a pipe 4 with valve 9,
continually draws by a pipe 5 connecting the upper end of the regulator, a larger
volume of gas from the regulator than can be supplied by the absorptionmeters.
The deficiency is supplied through the tube f, f, depending centrally within said
regulator. This tube is immersed into the water in the regulator to a depth of
two feet and being open at both ends communicating with the atmosphere at its
upper end. As soon as the aspirator decreases the tension in the regulator, the
atmospheric pressure will correspondingly depress the water in the tube, This
continues until the air bubbles up through the liquid column in the regulator, in
which manner the tension is maintained constant.
The manometer h₂ connects with the top of the regulator and indicates the
tension therein. Since the tension in the regulator depends upon the water column
in the tube ff, the latter is provided with a rack and pinion 20 at its upper end,
by means of which it can be raised or lowered in order to regulate the tension.
The bottom of the regulator is provided with a pipe 6 for supplying and drawing
off the water by means of the stop cocks 7 and 8.
The tension in the regulator is not absolutely constant but is, by a certain
amount, lower than that of the atmosphere, which, for the apparatus however,
is equivalent to a constant tension, since the gas enters the apparatus under
atmospheric pressure. The flow of gas is divided behind the stop-cock a¹ the
greater part passes through the specific gravity meter S, the remainder into the
absorption meters C, C The specific gravity meter S may consist of any
suitable instrument for the purpose.
We illustrate the form known as the Durre
Siebert Dasymeter, which consists of a glass case, which is constantly kept filled
with the gas mixture to be analyzed which continuously flows through it.
In the case is located a scale 10 upon which a hollow sphere 11, filled with air
is balanced. According as the passing gas is of higher or lower specific gravity,
the ball will weigh more or less and the specific gravity will thereby be continuously
indicated by a pointer 12 on a proper index, and can be read off as often as desired.
The smaller portion of the gas passes through the filter D, which is composed of
two compartments separated by gauze disc 13 made of platinum. This con-
struction makes it possible to clean the lower compartment without disturbing the
upper, which rarely requires attention. In this filter the last traces of fine dust
are removed, which is necessary in order to prevent clogging of the minute
apertures. After leaving the filter the gas is divided into two parts, one flowing
through the pipe 6', ', to the absorptionmeter C₁ to be analyzed for carbon
dioxide, the other through pipe b₁₁₁₁ to absorptionmeter C to be analyzed for
carbon monoxide and after passing through the small apertures c' and c¹ respectively
enters the absorption chambers C¹, C².
These absorption chambers are formed of tubes c, and c', which are filled with
small fragments of material which is not attacked by the reagent, and which may
be glass or feldspar,-through which the reagents, a solution of caustic potash in
the tube, c, and a hydrochloric solution of cuprous chloride in the tube, ca
percolate, so that the gases come in contact with a large surface moistened by the
reagents.
The reagents are supplied from reservoirs 14 as shown and their flow through
pipes 15 is regulated by stop cocks ³, 1. They How out through waste pipes s'
and s, respectively into the vessels and s₁ and from there through the com-
municating tubes s and s₁ into the reservoirs 16 as shown. The gas mixture
flows up through the particles in the absorption chambers moistened by the

page_text: reagents, and the components to be determined are absorbed in the chamber
carbon dioxide and in the chamber 3 carbon monoxide. The remaining gases
pass respectively through the small apertures and c₁ by the pipes 17 into the
top of the regulator F, and from there they are sucked off through the tube 5, 5,
by the aspirator (i.
The manometers and which are respectively connected by the tubes 18.
with the absorption chambers between the absorption tubes c³ and c', and the
apertures and c₁, serve to measure the tensions, between the apertures, which
depends upon the percentages of the gases absorbed.
A cylinder and 3, is used with each of these manometers and is provided with
an index which graphically represents the percentages of the component of the
gas absorbed, indicated by the tension for every specific gravity of the total gas
mixture. These cylinders which rotate about an axis supported by the brackets 19
are placed directly behind the manometers ², P.
In the graphical index the specific gravities are represented as abscisses and the
tensions depending thereon are represented by the ordinates. In this manner
curves representing the percents are obtained. Figure 3 shows in development
the principle of such an index. Whenever the exact composition of the gas is to
be observed the abscisses corresponding to the specific gravity of the gas mixture,
which is indicated by the specific gravity meter S, are placed opposite the
respective manometer tubes and by simply turning the cylinders about their
axes the required extent and the percentages directly read off. The composition
of the gas may however vary very largely without a change in the specific gravity
in the gas mixture. It is therefore only necessary to move the index when the
specific gravity meter indicates a change of specific gravity.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :
1. The herein described method of analyzing gases and determining a con-
stituent thereof, which consists in continuously passing the gas to be analyzed by
means of constant pressure through an absorption chamber having a minute inlet
and a minute outlet aperture, second, abstracting the said constituent from the gas
during its passage through said absorption chamber whereby a change from the
normal tension is caused therein and using this change of the tension as a measure
for determining the percentage of said constituent.
2. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in continuously passing the gas to
be analyzed under constant pressures through a corresponding number of absorption
chambers, each of which is provided with a minute inlet and outlet aperture, second
abstracting in each of these absorption chambers a constituent from the gas during
its passage through the respective absorption chambers, whereby changes from the
normal tensions are caused therein and using these changes as measures for
determining the percentages of the different constituents required.
3. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in continuously passing the gas to
be analyzed through a corresponding number of absorption chambers, each of
which is provided with a minute inlet and outlet aperture, abstracting continuously
in each of these absorption chambers by a suitable reagent a constituent from the
gas during its passage through the respective absorption chambers, thereby causing
changes from the normal tensions and using these changes as measures for deter-
mining the percentages of the different constituents required.
4. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in cleaning the gas, then passing
it through an absorption chamber having minute inlet and outlet aperture and
abstracting from the gas, during its passage through the said absorption chamber
a constituent whereby a change of tension from the normal is caused therein and

page_text: using this change of tension as a means to determine the percentage of said
constituent.
5. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in continuously passing the gas to
be analyzed through a filter and a corresponding number of absorption chambers,
each having a minute inlet and outlet aperture, and abstracting from the gas during
its passage through each of the said absorption chambers a constituent, whereby
changes from the normal tensions are caused in each and using these changes as
measures to determine the percentages of the different constituents required.
6. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in passing the gas to be analyzed
under a normal tension through an absorption chamber having minute inlet and
outlet aperture, second, abstracting a constituent from the gas during its passage
through said absorption chamber whereby a change in tension from the normal is
caused therein and using this change in tension as a measure to determine the
percentage of the said constituent, third, drawing off the gas from the said
absorption chamber at a tension less than the normal and antomatically regulating
the said tension whereby said tension remains unchanged.
7. The herein described method of analyzing gases and determining a constituent
thereof, which consists in determining the specific gravity of the gas to be
analyzed and passing it through an absorption chamber having a minute inlet and
a minute outlet aperture, abstracting the required constituent from the gas during
its passage through such absorption chamber whereby a change from the normal
tension is caused therein, and using this change of tension in connection with the
specific gravity indication to determine the percentage of the abstracted
constituent.
8. The herein described method of analyzing gases and determining the different
or required constituents thereof, which consists in determining the specific gravity
of the gas, and continuously passing it through a corresponding number of
absorption chambers each of which is provided with a minute inlet and outlet
aperture, abstracting in each of these absorption chambers a constituent from the
gas during its passage through the respective absorption chambers, thereby causing
changes from the normal tensions and using these changes in connection with the
specific gravity indication to determine the percentages of the abstracted
constituents.
9. In an apparatus for analyzing gases and determining the percentages of
different constituents thereof, an absorption chamber having a minute inlet and
outlet aperture through which the gas to be analyzed is passed under a normal
tension, a manometer connected with said absorption chamber to determine the
change of tension of the gas therein from the normal, and a regulator connected
with the minute outlet aperture to cause the gas to be drawn from the said
absorption chamber at a uniform tension.
10. In an apparatus for analyzing gases and determining the percentages of
different or required constituents thereof, a corresponding series of absorption
chambers, each having a minute inlet and outlet aperture, and a manometer con-
nected with each absorption chamber to indicate the change of tension of the gas
therein from the normal caused by the abstraction of a constituent, and a single
regulator connected with each of said absorption chambers to cause the gas to be
drawn through the said outlet apertures at a uniform tension.
11. In an apparatus for analyzing gases and determining the percentages of
different or required constituents by continuous process, the combination with au
absorption chamber, a tube having ininute inlet and outlet apertures, a manometer
and a specific gravity meter in communication, the manometer indicating the
change in tension from the normal caused by abstracting a constituent from the
gas, of a graphical scale graduated to correspond with the differences and changes
in tension and specific gravities to be applied to the manometer to enable the
percentage of the required constituent to be read off.

page_text: 12. In an apparatus for analyzing gases and determining the percentages of the
different or required constituents thereof, the combination of an absorption
chamber, a manometer connected therewith, a specific gravity meter in communi-
cation, and a graphical scale applied to the manometer and movable therewith to
enable the percentages of the required constituent to be read off with reference
to the specific gravity of the gas mixture.
13. In an apparatus for analyzing gases and determining the different or required
constituents thereof, the combination of an absorption chamber, a manometer, in
connection therewith, a specific gravity meter in communication, and a cylinder
mounted behind the manometer and movable about an axis and provided with a
graphical scale whereby the percentage of the required constituent can be read off
with reference to the specific gravity of the gas.
14. In an apparatus for analyzing gases and determining the different or
required constituents thereof, the combination of an absorption chamber, a
manometer connected therewith, and a regulator connected with the outlet
aperture of the absorption chamber and comprising a fluid containing receptacle
and a vertically adjustable tube open throughout its length and external to said
receptacle at its upper end and an aspirator connected with the regulator.
15. In an apparatus for analyzing gases, an absorption chamber for containing
an absorbent and having a minute inlet and outlet, and a manometer having
communication with the absorption chamber to indicate the change of tension of
the gas between the said minute inlet and outlet caused by the absorption of the
constituent, the percentage of which is to be determined, substantially as
described.
16. An apparatus for analyzing gases consisting of an absorption chamber
having a minute inlet and outlet, a receptacle or reservoir connected with the
upper end of the absorption chamber for supplying an absorbent to said absorption
chamber, and a manometer having communication with the said absorption
chamber and reservoir, substantially as described.
17. An apparatus for analyzing gases in which the percentages of any number
of constituents are indicated by the difference in tension, an absorption chamber
arranged between a minute inlet and outlet through which the gas passes in the
way described, and a manometer having communication with the said absorption
chamber between said inlet and outlet, substantially as described.
18. An apparatus for the analyses of gases, which indicates continuously and
automatically the variation in the composition of any gas by the change in tension
caused by the absorption of the constituent, consisting of an absorption chamber
between a minute inlet and outlet, a manometer for indicating this variation of
tension, having cominunication with said absorption chamber between the inlet and
outlet in the way described and a manometer indicating the initial tension of
the gas.
19. An apparatus for analyzing gases consisting of a connected series of
absorption chambers suitable inlets therefor connected with a source of supply of
the gas to be analyzed, suitable outlets connected with a partial vacuum of constant
tension, both inlets and outlets provided with minute apertures, a manometer
connected with the outlets, and a manometer connected with the said absorption
chambers between the said inlets and outlets, substantially as described.
20. An apparatus for analyzing gases consisting of an absorption chamber
containing non-corrodible particles, and having receptacles connected with its
opposite ends to supply the fresh and receive the saturated absorbent, respectively,
a manometer having connection with the absorption chamber and with said
receptacles, means for passing the gas through the absorption chambers under
tension, diaphragm plates having minute apertures which constitute, respectively,
the inlet and the outlet to the absorption chamber, and an indicator to register the
tension of the gas, substantially as described.
21. The apparatus herein described and for the purpose stated consisting of a
corresponding series of absorption chambers, each having a minute inlet and outlet

page_text: aperture, a manometer for each absorptionmeter a pipe for supplying the gas to
the absorption chambers under a constant tension, a filter for cleaning the gas, a
specific gravity meter in communication with said pipe, a regulator connected with
the outlet apertures of the absorption chambers and graphical scales movable on
the manometers to facilitate reading off the percentages of the required
constituents.
Dand this 7th dor of Me 1001
W. P. THOMPSON & BOULT,
Agents for the Applicants.