sample. Unnecessary absorptions should not be made as small decreases in volume will be
observed due to solubility of specific components other than the specific reaction the absorbent
is intended for. Care must also be taken that each absorption is complete.
B. Avoiding unnecessary passes will also expedite the absorption procedure.
C. NOTE: When performing analyses, it is important that the operator always observe the level of
rising fluid, such as the confining solution, to ensure that the fluid does not “overshoot” the
capillary and contaminate the other pipettes.
Analysis of gas samples using the Orsat consists of three general processes. These are 1) preparing the
analyzer to analysis by purging with the sample to be analyzed, 2) loading the analyzer with a 100-ml gas
sample and zeroing the burette, and 3) passing the gas sample through the absorption pipettes recording
the reduction in sample volume. To analyze sa mples using the VSC-33 Orsat apparatus, proceed as
follows:
I. Analytical Technique
1. Prepare the Orsat Analyzer for Analysis.
a. Set the valves on each of the absorption pipettes to the bypass position. Indicating marks on all
pipette stopcocks should be pointing upward. (Figure 6, Position A.)
b. Connect the container containing the gas sample to the inlet leg of the burette stopcock using a
short piece of the supplied rubber tubing. Open the burette stopcock to the gas sample. The
indicating mark on the stopcock valve should be pointed towards the gas sample container.
(Figure 6, Position C.)
c. Lower the leveling bottle, to allow the confining solution to flow from the burette into the leveling
bottle. When the level of the confining solution falls below the zero mark, crimp the rubber hose
connecting the leveling bottle with the burette to quickly stop the flow of the confining solution.
d. Turn the valve on the burrette so that the gas flow is open the bypassed carbon monoxide
pipette. (Figure 6, Position B). Raise the leveling bottle so that the confining solution rises in the
burette and expels the gas sample through the stopcock valves of the absorption pipettes, to
ambient air. When the level of the confining solution reaches the glass capillary tubing, crimp the
rubber tubing.
e. Repeat steps b, c, and d two additional times to ensure that the burette is completely flushed with
the gas sample.
2. Load the analyzer and zero the burette.
a. Connect the gas sample container to the burette and open the burette stopcock to the sample
container. (Figure 6, Position C). Lower the le veling bottle so that the confining solution flows
out of the burette and into the leveling bottle. When the confining solution reaches the zero mark,
crimp the rubber tubing, and use the leveling bottle to adjust the level of fluid in the burette so that
the bottom of the meniscus is at the zero mark on the burette.
b. Close the stopcock on the burette. Allow the sample to thermally equilibrate for a period of about
three minutes.
3. Pass the gas sample through the absorption pipettes for gas analysis.
a. Open the stopcock on the burette to the carbon dioxide absorption pipette, and open the
stopcock on the carbon dioxide absorption pipette. (Figure 6, Position B for burette valve
position, and Valve Position C for the CO
2
pipette valve position).
b. Raise the leveling bottle so that the confining solution fills the burette. When the confining
solution reaches the top of the capillary, crimp the rubber tubing. Lower the leveling bottle, being
VSC-33
APEX INSTRUMENTS, INC.
14
To Next Page
Loading...
