Nathaniel Wright Lord.

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bottle on a support a little above the level of the zero point.
Pinch the rubber near the bottom of the. burette, open the cock
to the side and carefully let the liquid run in by releasing the
pressure of the fingers until it reads exactly zero on the tube.
Now close the cock carefully, take down the bottle, and read the
volume of the gas after equalizing the pressure by bringing the
surface of the liquid in the bottle to the level of that in the tube.
The reading should be exactly zero. If it is 0.1 or 0.2 c.c. off,
this can be corrected by raising or lowering the level of the water
in the pressure bottle until the reading is zero, and making all



subsequent readings in the analysis after giving the leveling
bottle the same relative elevation.

The measuring tube now contains 100 c.c. of gas. Open the
stop-cock into the potash bulbs and run the gas over by raising
the pressure bottle. Be careful to so hold the bottle that the
liquid will rise only to the mark in the gas tube. Now draw the
gas back in the same way, run it over again and again back.
Bring the potash solution carefully to the mark in its tube, close
the stop-cock, wait at least 30 seconds for the liquid to drain
down the side, level as before and read the volume. Transfer
a second time to the potash, draw it back and read the volume
again. If it does not agree with the first reading, run it over a
third time. With fresh potash solution, the second reading
should always check the first. The decrease in volume is the
CO2. Now proceed in the same way with the other tubes, using
the pyrogallic solution first and then the cuprous chloride. With
the pyrogallate tube, the gas should be run over two or three
times rapidly before taking a reading, so that the dark saturated
solution forming on the walls of the bulb may not remain long in
contact with the gas, as this might lead to the formation of CO.
The liquid draining down the side of the bulb will show by its
change of color when it is absorbing oxygen. As soon as the
oxygen is all absorbed, the liquid on the sides of the bulb will
not turn brown as the gas reaches it. Always get two readings
that agree before proceeding to the next tube. The correspond-
ing decreases in volume give the oxygen and the CO. The resid-
ual gas is estimated as N 2 . It will contain any H 2 and CH 4
present in the original gas, but these are rarely present in chimney
gases in measurable amounts. When the analysis is finished,
run out the residual nitrogen, leaving the measuring tube full
of water. Now everything is ready for the next test.

Extreme care should be taken to avoid getting any of the absorption
solutions into the connection or measuring tubes. Should this happen,
they must be washed out and the water in the pressure bottle changed
before starting a new analysis, as gas might be absorbed in filling the
apparatus. The Orsat's apparatus may be used for the determination
of C02 and CO in the gas from the iron blast furnace. In this case
the residual gas invariably contains hydrogen and methane and should
be kept for further analysis.


If the pipettes are of the ''bubbling" type, the absorption is more


These two gases are analyzed in the same way. The writer prefers
the Hempel apparatus for the analysis of these gases rather than special
built up apparatus, because the Hempel is more convenient and is accu-
rate. It is the writer's experience that results with the Hempel appa-
ratus can with care be made accurate to 0.05 per cent. When greater
accuracy than this is desired it is necessary to use some form of apparatus
such as the one evolved by Mr. Burrell of the Bureau of Mines and shown
on page 291, or such as the Haldane apparatus. The complete analysis
of a producer gas can be made in less than a half hour. What was said
concerning sampling and storage of gas at the beginning of this chapter
applies here. If the sample is taken over water, as when a long time
sample is taken, the surface of the water must be covered with paraffin

Apparatus Used. A is a single pipette containing 30 per cent,
solution of KOH used for absorbing CO 2 . B is a pipette filled
with fuming sulfuric acid. The small upper bulb is filled with
glass beads in order to give a larger surface of contact between
the gas and the acid. This is used for absorbing the "illumi-
nants" or unsaturated hydrocarbons such as ethylene, C2H 4 ,
propylene, C 3 H 6 , etc. C is a double pipette containing alkaline
pyrogallate for oxygen. D D, double pipettes containing am-
moniacal cuprous chloride, are precisely the same as C. It is not
necessary to use both on gases containing but traces of CO but
if the gases are blast-furnace gas, or producer gas, or coke-oven
gas, or water gas it is necessary to use two cuprous chloride
pipettes and even three are sometimes used. E is a combustion
pipette containing a platinum spiral which can be heated with an
electric current. It is made from a single pipette for solid
reagents. One bulb has been cut off and used for the leveling
bulb. A capillary tube with a stop-cock is attached. The pi-
pette is filled with mercury and connected to a leveling bulb with
heavy rubber tubing. The combustion pipette sets in a basin to
catch the mercury should the tube break. F is the burette con-
nected with a leveling bottle G. The burette must be water
jacketed and a thermometer should hang in the water of the
jacket. It is convenient to have the stop-cock a three-way one



but not necessary. H is a capillary tube with an internal diame-
ter between 0.5 and 1.0 mm. or about J4o m -

The rubber tubes on the pipettes should be made of thick-
walled pure gum and should be wired to the pipettes by passing
the wire around twice or more to prevent leakage. The rubber

tube should project beyond the end of the capillary of the pipette
about 1 JfJ in. but not so long but that the air in the tube can be
driven out by squeezing it between the thumb and forefinger.
Also, and this is important, the tube should have a band of elas-
tic rubber about it as shown in the cuts, in order to make a tight


connection when the capillary on the burette is pushed in the
tube. This band is put on as follows: Cut a piece of pure gum
tubing a little smaller in diameter than the rubber tube on the
pipette and about a quarter of an inch long. Push this on a
tapering glass tube (P, Fig. 21) until it is at the big end, which
should be as large in internal diameter as the rubber tube on the
pipette. Push the rubber tube into the glass tube about Y in.
and then push the rubber band off the glass tube onto the rubber
tube. This will make the burette capillary fit in the rubber
tube without leaking gas and without the bother of tying the
connection each time.

Filling the Pipettes. To fill the single pipettes, simply pour
the reagent in the large tube L until there is enough to fill the
bulb M and to have about J in. of the reagent in the other bulb.

To fill the double pipettes, first .pass an oxygen and carbon
monoxide free gas, such as natural gas or hydrogen, through the
pipettes until the air is displaced. Then attach to the capillary
of the pipette a rubber tube the end of which dips into the re-
agent which is to be put in the pipette, then suck on the other end
of the pipette until enough of the reagent has entered .to fill the
first bulb full and about K in. in the second. A little experience
makes this easy. Then pour into the rear bulb 125 c.c. of water
to act as a water seal to keep out the air. The purpose of filling
the bulbs with a neutral gas is to prevent the weakening of the
reagent by air in the bulbs.

The reagents are prepared as directed on page 271 et seq.

Process of Analysis. First see that the water in the burette
jacket is at the same temperature as that in the leveling bottle.
The water in the leveling bottle should be shaken with some gas
similar to that to be analyzed and so should the absorption solu-
tions in the pipettes in order to saturate the liquids with the gas
other than the constituent to be absorbed in the solution. This
is most readily done by making a preliminary analysis of the gas.
Then see that the burette is tight by taking a reading, then raising
or lowering the pressure bottle and allowing the gas to stand
under a pressure or vacuum for several minutes. Then take
another reading. The readings ought to agree exactly. In
reading the burette hold a finger or piece of paper back of the
burette and a little below the meniscus so as to illuminate the


bottom of the meniscus and make the reading sharp. With care
one can be sure of the reading to within less than 0.05 c.c. The
water in the pressure bottle should contain about 0.5 per cent.
H 2 S0 4 .

Now raise the pressure bottle until all gas is out of the burette
and water drops from the end of the capillary. Also wash the
capillary by dipping the end of it in acidulated water to remove
all alkali. Then attach the rubber tube of the vessel containing
the sample to the burette capillary, first taking care to drive all
air out of the rubber tube. Then lower the pressure bottle of
the burette and raise the pressure bottle of the vessel containing
the sample and open the stop-cock on the burette and draw in
the gas until a little more than 100 c.c. has been drawn in. Close
the stop-cock and detach the sample vessel. Allow the burette
to drain about 30 seconds. Raise the pressure bottle until the
bottom of the meniscus is just on the zero (or 100 c.c.) mark,
pinch the rubber tube connecting the burette and bottle and open
the stop-cock momentarily to put the gas under atmospheric
pressure. Close the cock and level the water in the burette ex-
actly with the water in the bottle and take the reading. It
should read exactly zero (or 100 c.c.). At the same time read the
temperature of the jacket water.

Now attach the KOH pipette to the capillary of the burette
as follows: squeeze the rubber tube on the pipette between the
thumb and forefinger so that all air will be driven out of the tube
and the KOH will fill the capillary of the pipette. Then push
the capillary of the burette into the rubber tube in such a way
as not to drive air into the tube and until the ends of the capil-
laries are in contact. The KOH should extend nearly to the
top of the pipette capillary. Make a mental note of its position.
Now open the stop-cock and raise the pressure bottle and drive
all the gas over into the pipette. Close the cock and shake the
KOH pipette vigorously for 20 or 30 seconds, then raise the pres-
sure bottle and run a few drops of water into the pipette to wash
all KOH which was splashed into it out of the capillary. Then
lower the pressure bottle and draw the gas back into the burette
until the KOH rises in the capillary of the pipette exactly to the
same height as it was at the beginning. Allow the burette to
drain as long as before and take the reading of the burette care-


fully, also read the temperature of the jacket. The decrease in
volume (if there has been no temperature change) is the percent-
age of CO 2 in the gas. To make sure that the CO 2 is all absorbed
repeat the above operation. The reading should be the same as
before. If not, run a blank determination by again repeating
the operation of driving the gas into the KOH pipette, etc., and
again read the burette after the usual draining. If there is a
further change of volume, either positive or negative, it shows
that there is a leak or that the temperature is -changing. Twice
this change in volume should be added to or subtracted from the
second reading. By taking this trouble of running a blank the
results can be relied upon to 0.05 per cent. For most technical
work such care is not necessary but should be taken occasionally
to check up the work.

Now remove the KOH pipette and attach the fuming sulfuric
acid pipette in the same way, making mental note of the position
of the acid in the capillary. The connection must be especially
tight as it requires considerable pressure to drive the gas into
this pipette. Raise the pressure bottle and drive the gas into
the burette but do not let any water get into the sulfuric acid pipette.
Pass the gas back and forth between the burette and pipette
three times, then bring the sulfuric acid back to the original place
on the capillary. The gas now has sulfuric acid vapors in it
which must be removed by passing the gas into the KOH pipette
and shaking vigorously. Finally bring the gas back into the bu-
rette and read the change in volume and temperature. If there
has been no temperature change, the decrease in volume is the
percentage of "illuminants," chiefly C 2 H 4 . The C 2 H 4 is changed
into ethienic acid, C 2 H 6 S 2 O 7 . Any acetylene is changed to
C 2 H 4 SO 4 and benzene to CeHeSOs. Since blast-furnace gas con-
tains no heavy hydrocarbons the fuming sulfuric acid is not used
when blast-furnace gas is analyzed.

It is well to run a blank on this determination occasionally.

Next attach the pyrogallate pipette and manipulate just as
with the KOH pipette except that the shaking of the gas in con-
tact with the solution should be much longer. The decrease in
volume is the percentage of oxygen. To make certain of com-
plete absorption of the oxygen it is necessary to run the gas into
the pipette again. There should be no change in volume.


Next attach the ammoniacal cuprous chloride pipette and
manipulate as with the pyrogallate pipette. The CO is absorbed
slowly and the pipette should be shaken at least 100 times, and if
the cuprous chloride has been used before, the gas must be run
into a second cuprous chloride pipette and shaken 100 times.
This is always the best way if the gas contains more than 2 per
cent, of CO. When the first pipette gets too slow in its action, it
is emptied and filled with fresh solution and used as the second
pipette while the other one is used first.

The gas now has left in it only hydrogen, methane, and

The hydrogen and methane are determined by combustion in
the combustion pipette. They may be determined by explosion
in an explosion pipette but the writer does not like the explosion
method. The combustion method is carried out as follows:
Attach the combustion pipette to the capillary of a burette con-
taining oxygen and run in enough oxygen to uncover the platinum
wire and its connections, but do not use more than 40 c.c. Meas-
ure the oxygen carefully and the temperature of the burette from
which it was taken. Close the stop-cock of the pipette and attach
it to the capillary of the burette containing the gas. Connect the
wires from a source of electricity to the terminals of the wires of
the combustion pipette. Turn on the current until the plati-
num wire in the pipette is at a dull yellow of nearly the same
brightness as an ordinary incandescent light carbon filament.
Record the temperature of the gas, then open the stop-cocks on
the burette and the pipette and run the gas into the pipette slowly,
in order, in the case of producer gas, to prevent an explosion or
melting of the platinum. The mercury in the leveling bulb of the
pipette should be at about the same level as the mercury in the
pipette in order to avoid leaks due to the great pressure caused by
considerable difference in levels of the mercury. After the gas is
all in the pipette, close the pipette stop-cock and continue the
combustion for several minutes. The pipette should be kept cool
during the combustion by water dripping on the cotton, N Fig. 21,
around the top. Now shut off the electric current and run the
residual gas back into the burette. Allow the gas to cool a min-
ute and then read the volume and temperature. If there has been
any change in temperature make the proper correction. Call the


contraction in volume C. Now attach the burette to the KOH
pipette and determine the CO 2 produced by the burning of the
CH 4 . The methane in the gas was the same in volume as the
CO2 produced by its combustion, and since the original sample
was 100 c.c. the volume of C0 2 produced in cubic centimeters is
the percentage of methane in the gas sample. The contraction
in volume due to the burning of the methane is twice the volume
of the methane, and this contraction subtracted from the total
contraction C on burning gives the contraction due to the burning
of the hydrogen, which multiplied by % gives the volume and
percentage of the hydrogen.

The reactions are: CH 4 (1 vol.)+20 2 (2 vol.)=C0 2 (l vol.) +
2H 2 O. Since the H 2 O condenses, the contraction is twice the
CH 4 .

2H 2 (2 vol.)+O 2 = 2H 2 O. Since the H 2 O condenses, the
hydrogen is equal to two-thirds of the contraction when it is

The total time required for the analysis of the gas is about 25

Notes on the Process. The two cuprous chloride pipettes may be
permanently connected by means of a T capillary, with a stop-cock in
each branch going to a pipette, and the third branch connected to
the burette. In this way only one operation of connecting the cuprous
chloride pipettes to the burette is necessary, although each pipette
works separately.

If the stop-cock on the burette is a "two-way" one it is convenient
to attach the KOH pipette permanently to one of the ways because the
KOH pipette is used three times during the analysis, and a permanent
attachment of it saves the time of three operations. This idea has
been carried out to the extent of having a stop-cock with enough
different "ways" to have a permanent attachment for each pipette.

After each time that a pipette is connected to the burette a drop of
water should be placed on the top of the rubber connection, so that if
the connection is leaking the bubbling of gas through the drop may be

The combustion pipette should hold about 150 c.c. The platinum
wire should be inserted far enough in so that 40 c.c. of gas in the pipette
will uncover the wire and prevent the mercury from short-circuiting
the current. It is best to wrap the top of the pipette with cotton
and keep water dripping on the cotton during the combustion so that


the glass will not get so hot that it is liable to crack. The pipette
must be surrounded with a wire netting or gauze so that the eyes of
the operator will be protected if an explosion should take place. It
is convenient to have a stop-cock on the combustion pipette, but is not
necessary. If a stop-cock is not used, it is necessary to close the rubber
tube on the capillary with a glass plug when the pipette is moved from
the oxygen burette to the burette containing the gas.

The electric connections for the platinum wire are easily made as
follows: To the end of a copper wire about 6 in. long fasten a piece
of platinum wire of 20 gage and 1 in. long and pass it through a piece
of glass tubing 5 in. long and y in. internal diameter. Inside this
tube pass a smaller glass tube with another copper wire with plati-
num end. The platinum wires should project % in. beyond the end of
the larger glass tube which should be 1 in. longer than the other. Now
heat the large glass tube so that the glass will soften and the end will
close about the platinum wires. It is well to squeeze the softened glass
with a pair of pliers to close the ends perfectly and to leave no
thick ball of solid glass which is apt to crack when heated. The other
end of the outer tube should be constricted so that the inner tube will
not fall out. Pass the tubes through a hole in a rubber stopper which
fits the opening in the bottom of the combustion pipette. Connect
the platinum ends with a 30-gage platinum wire, about 1>^ in. long and
coiled in several coils. The platinum coil should be about % in. from
the top of the pipette. It is best to provide a second platinum coil in the
pipette, connecting it to one of the terminals above described and to an
iron rod passing through the mercury and the stopper. Then if one coil
melts, the other can be used.

The platinum wire must be heated to a dull yellow or the combus-
tion is likely to be incomplete. The wire may be heated by about
three or four dry cells or better by the current through six 16-candle-
power electric lights placed in parallel on a 110-volt circuit. That is,
a current of about 3 amperes is required, depending, of course, on the
diameter of the wire. If the wire is heated hotter than a dull yellow
a slight error is caused due to formation of N 2 O4.

When a gas contains ethane as well as methane and hydrogen, which
is not the case with producer or blast-furnace gas, the hydrogen must be
determined separately as directed under the analysis of coke-oven gas.
Of course the hydrogen in producer or blast-furnace gas may be de-
termined separately, but this is not necessary. If the gas contains
hydrogen and no methane the combustion pipette may be filled with
water instead of mercury. Blast-furnace gas contains only about 0.2
per cent, methane. If the gas contains both hydrogen and methane
and the hydrogen is removed first, the combustion of methane may
be made without mercury.


Gas Analysis without use of Cuprous Chloride. Instead of absorbing
the CO in cuprous chloride and then determining the hydrogen and
methane by combustion, the carbon monoxide, hydrogen and methane
may be all determined together by combustion without having to use
the cuprous chloride. This applies only to gases like producer and blast-
furnace gases which have no hydrocarbons higher than methane.

Process of Analysis. Carry out the combustion exactly as
above directed. Measure the decrease in volume after combus-
tion, and then determine the CO 2 produced by the combustion by
passing the residue into the KOH pipette. Then determine the
amount of oxygen left after the combustion by absorbing it in
pyro solution. Also carefully determine the amount of oxygen
in the volume of oxygen used by passing the same volume of
oxygen through the pyrogallate pipette. The difference between
the two gives the amount of oxygen used. Calculate the results
as follows : The reactions of combustion are as given above for
hydrogen and methane and as follows for carbon monoxide:
2CO (2 vol.)+0 2 (l vol.) =2C0 2 (2 vol.). Let x = hydrogen, y =
methane and z = carbon monoxide. Then we have the fol-
lowing equations:

Contraction during combustion = %x+2y4- }^z.
Carbon dioxide produced y-fz.

Oxygen consumed = J

Combining these equations we get the relations:

Hydrogen = contraction minus oxygen consumed.

Methane = oxygen consumed minus ^ contraction minus %
CO 2 produced.

Carbon monoxide = % CO 2 produced plus J contraction
minus oxygen consumed.

Notes on the Process. This method requires less time for manipula-
tion but more time for calculation than the one previously given. They
are about equally accurate.

There is a correction necessary for accurate work when a gas is
burned which gives a large amount of C02. It is due to the fact that
the molecular volume of CO 2 is 22.26 liters while that of CH 4 is 22.44
liters and of CO is 22.39 liters. That is, the C0 2 produced by burning
100 c.c. of methane is 99.20 c.c. instead of 100 c.c., because CO 2 departs
considerably from being a perfect gas. So that when CO or CH 4


are burned, the contraction in volume should be corrected by subtracting
from it 0.8 per cent, of the volume of C0 2 produced and the volume
of the C0 2 should be increased by 0.8 per cent, of the measured amount
of C0 2 in order to calculate the volume of the methane or the CO.

The determination of dust in unwashed blast-furnace gas is an
exceedingly difficult proposition. For the apparatus and details used
for this determination see TOUZALIN and BRADY, Jour. Ind. Eng. Chem.,
Ill, pp. 662-670.


The methods described above are, in the author's opinion, very re-
liable and accurate. However, H. H. Worrell recommends Jiiger's
method modified. (See Met. Chem. Eng., XI, 245.) In outline it is
as follows: Analyze the gas just as above described until the oxygen
is removed. Then connect between the burette and a single Hempel
pipette filled with acidified water, or, better, with mercury, a silica tube,
Y in. bore by 7 in. long. This tube is filled with copper oxide and sur-
rounded with an air bath (Eimer and Amend catalogue No. 2073).

Online LibraryNathaniel Wright LordMetallurgical analysis → online text (page 26 of 32)