10. Procedure
10.1 Lower the mercury level from the collection flask.
10.2 Evacuate the system of collection flask and degassing flask to an absolute pressure of 13 10/-3 torr (130 mPa) or less. (In Fig.1, the space above the mercury in the reservoir must also be evacuated.)
10.3 Connect the oil sample syringe by the PTFE tubing to the three-way stopcock leading to the degassing flask.
10.4 Flush a small quantity of oil from the syringe through the tubing and stopcock to waste, making sure that all the air in the connecting tubing is displaced by oil.
10.4.1 Any gas bubbles present in the syringe should be retained during this flushing operation. This may be accomplished by inverting the syringe so that the bubble remains at the plunger end of the syringe during the flushing operation.
10.5 Close the stopcocks to the vacuum pumps and then slowly open the three-way stopcock to allow oil and any gas bubbles that may be present from the sample syringe to enter the degassing flask.
10.6 Allow the desired amount of oil to enter the degassing flask and operate the magnetic stirrer vigorously for approximately 10 min. This is the volume, Vo used in the calculation in 15.4.
10.6.1 If a gas bubble is present in the syringe, either analyze the total content of the syringe including the bubble; or, if the gas bubble is large, and it is suspected that the concentration of dissolved gases is high, measure and analyze the gas bubble separately, extract an aliquot of the oil sample, and correct as applicable.
10.7 Close the stopcock isolating the collection flask, and allow mercury to flow into the collection flask.
10.8 Open the stopcock to the reference column and by means of the hand pump (Fig.1) or leveling bottle (Fig.2) bring the level of the mercury in the reference column even with the level in the collection tube.
10.9 Measure the volume of extracted gas in the collection tube, and correct for collection efficiency by dividing it by the volumetric collection ratio calculated in 9.2. Correct to 760 torr (101.325 kPa) and 0°C. Determine the volume of oil degassed in the degassing flask. Record the gas content as a percentage of the oil by volume.
10.10 Because the total concentration of gas is not extractable from the oil, a rinse step may be required when high quantities are present. The extractor can be rinsed with oil containing nondetectable quantities of gases, except for those present in air. The amount of rinsing needed will be dependent upon the gas concentration, type (solubility in oil), and efficiency of the extractor. To ensure that the combustible gases have been sufficiently removed from the extractor, the rinse oil may be treated as a sample. General rinse procedures may be established. However, for samples with very high concentrations of gases, verify effectiveness of the rinse procedure.
