aratus for Flue Gas Analysis--The Orsat apparatus, illustrated in
Fig. 22, is generally used for analyzing flue gases. The burette A is
graduated in cubic centimeters up to 100, and is surrounded by a water
jacket to prevent any change in temperature from affecting the density
of the gas being analyzed.

For accurate work it is advisable to use four pipettes, B, C, D, E, the
first containing a solution of caustic potash for the absorption of
carbon dioxide, the second an alkaline solution of pyrogallol for the
absorption of oxygen, and the remaining two an acid solution of cuprous
chloride for absorbing the carbon monoxide. Each pipette contains a
number of glass tubes, to which some of the solution clings, thus
facilitating the absorption of the gas. In the pipettes D and E, copper
wire is placed in these tubes to re-energize the solution as it becomes
weakened. The rear half of each pipette is fitted with a rubber bag, one
of which is shown at K, to protect the solution from the action of the
air. The solution in each pipette should be drawn up to the mark on the
capillary tube.

The gas is drawn into the burette through the U-tube H, which is filled
with spun glass, or similar material, to clean the gas. To discharge any
air or gas in the apparatus, the cock G is opened to the air and the
bottle F is raised until the water in the burette reaches the 100 cubic
centimeters mark. The cock G is then turned so as to close the air
opening and allow gas to be drawn through H, the bottle F being lowered
for this purpose. The gas is drawn into the burette to a point below the
zero mark, the cock G then being opened to the air and the excess gas
expelled until the level of the water in F and in A are at the zero
mark. This operation is necessary in order to obtain the zero reading at
atmospheric pressure.

The apparatus should be carefully tested for leakage as well as all
connections leading thereto. Simple tests can be made; for example: If
after the cock G is closed, the bottle F is placed on top of the frame
for a short time and again brought to the zero mark, the level of the
water in A is above the zero mark, a leak is indicated.

[Illustration: Fig. 22. Orsat Apparatus]

Before taking a final sample for analysis, the burette A should be
filled with gas and emptied once or twice, to make sure that all the
apparatus is filled with the new gas. The cock G is then closed and the
cock I in the pipette B is opened and th