sisting of a U-tube made from borosilicate glass 4 mm. in outside diameter, and packed with 0.2 gram of Burrell high-activity charcoal held in place with wads of glass wool and bent wire, is purged and sealed as in preparation of the sample tubes.The tube is unstoppered and cooled in ice water, and 20 liters of the air to be tested are aspirated through it at the rate of 0.5 liter per minute. It is then restoppered and kept at reduced temperature until time of analysis. Samples may be stored for 2 to 3 weeks without apparent loss.Analysis. The sample is transferred to the analytical column by connecting the sampling tube to a magnesium perchlorate tube and then to the gas pipet and the chromatograph. The gas pipet and the perchlorate drying tube should first be flushed with helium. Desorption and transfer of the sample are accomplished by inserting the sampling tube in an oil bath maintained at 200°C. Simultaneously, the magnesium per-14, 121 (1953).(4) Jacobs, . B., "Analytical Chemistry of Industrial Poisons, Hazards and Solvents," 2nd ed., Interscience,