92 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Glass aerosols have excellent internal pressure strength if properly de- signed (over 600 lb. per sq. in.) but should always be plastic coated for safety. The plastic coating is very important in restraining the fragments if the container is broken. We also believe that the cold filling method is to be preferred in loading aerosols unless adequate purging is carried out with the pressure filling technique to remove entrapped air. Entrapped air is undesirable as it can increase the internal pressure considerably. In conclusion I would say that fundamental research in physics and chemistry and progress in engineering and design are contributing new ideas to the glass industry at a greater rate than ever before. Glass may be one of man's oldest structural materials but it is only now reaching a vigorous youth in research and development. GAS CHROMATOGRAPHIC ANALYSIS OF AEROSOL PRODUCTS* By M. J. Roo. and M. J. MAUP,¾ G. Barr & Company, Chicago 9, l//. ANALYZING the volatile components of an aerosol product by con- ventional analytical means is extremely difficult and time consuming We may determine the pressure or the specific gravity and arrive at a very crude analysis of the propellents present. A 1 per cent change in the com- position of a mixture of equal parts of Freon © 12 (dichlorodifiuorometh and Freon © 114 (tetrafiuorodichloroethane) produces a pressure change ofl only 8/4 lb. per square inch and a specific gravity change of0.0015. Measur- ing these physical properties to within such increments is not readilyl accomplished. Fluorinated hydrocarbon mixtures have been commonlyI analyzed by both mass spectrometry and infrared spectrophotometry, butl the presence of other volatile components makes even these costly methods of little value. Determining quantitatively, for example, ethyl alcohol in the presenc of trichloromonofiuoromethane and dichlorodifiuoromethane is extremelyl difficult. Although ethyl alcohol and trichloromonofiuoromethane, whichl boil at temperatures of 176øF. and 74.7øF., respectively, can be readily I separated by fractional distillation, the presence of dichlorodifiuorometh which boils at -21.6øF., introduces a complication. Not only must thel distillation flask, column and receiver be kept under a very high pressur * Presented at the December 13, 1956, Meeting, New York City.

92 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Glass aerosols have excellent internal pressure strength if properly de- signed (over 600 lb. per sq. in.) but should always be plastic coated for safety. The plastic coating is very important in restraining the fragments if the container is broken. We also believe that the cold filling method is to be preferred in loading aerosols unless adequate purging is carried out with the pressure filling technique to remove entrapped air. Entrapped air is undesirable as it can increase the internal pressure considerably. In conclusion I would say that fundamental research in physics and chemistry and progress in engineering and design are contributing new ideas to the glass industry at a greater rate than ever before. Glass may be one of man's oldest structural materials but it is only now reaching a vigorous youth in research and development. GAS CHROMATOGRAPHIC ANALYSIS OF AEROSOL PRODUCTS* By M. J. Roo. and M. J. MAUP,¾ G. Barr & Company, Chicago 9, l//. ANALYZING the volatile components of an aerosol product by con- ventional analytical means is extremely difficult and time consuming We may determine the pressure or the specific gravity and arrive at a very crude analysis of the propellents present. A 1 per cent change in the com- position of a mixture of equal parts of Freon © 12 (dichlorodifiuorometh and Freon © 114 (tetrafiuorodichloroethane) produces a pressure change ofl only 8/4 lb. per square inch and a specific gravity change of0.0015. Measur- ing these physical properties to within such increments is not readilyl accomplished. Fluorinated hydrocarbon mixtures have been commonlyI analyzed by both mass spectrometry and infrared spectrophotometry, butl the presence of other volatile components makes even these costly methods of little value. Determining quantitatively, for example, ethyl alcohol in the presenc of trichloromonofiuoromethane and dichlorodifiuoromethane is extremelyl difficult. Although ethyl alcohol and trichloromonofiuoromethane, whichl boil at temperatures of 176øF. and 74.7øF., respectively, can be readily I separated by fractional distillation, the presence of dichlorodifiuorometh which boils at -21.6øF., introduces a complication. Not only must thel distillation flask, column and receiver be kept under a very high pressur * Presented at the December 13, 1956, Meeting, New York City.