380 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V I Fill Tolerances for Propellant 142b/11 (50: 50) Systems No. Nom- Stan- Tolerance Limits a Tolerance Units inal Mean dard Exptl. (g) Limit Ana- Fill Fill Devia- Range Spread lyzed (g) (g) tion (g) (g) Lower Upper (g) 50 10 9.517 0.193 1.052 8.914 10.120 1.206 50 20 20.695 0.432 2.026 19.345 22.045 2.700 50 30 30.346 0.407 2.595 29.074 31.618 2.544 50 40 40.671 0.471 2.853 39.199 42.143 2.944 50 60 60.525 0.585 2.989 58.696 62.354 3.658 50 80 80.752 0.358 2.180 79.633 81.871 2.238 50 100 101.152 0.532 3.052 99.489 102.815 3.326 50 115 114.171 0.572 3.006 112.383 115.959 3.576 a The tolerance limits will be expected to contain 99% of the population with 95% con- fidence. propellant line pressure from 500 to 900 psig causes the only practical difference in propellant fill. As a check for aerosol leakage, various aerosol units were reweighed after the initial weighing in all three studies. Valve crimp parameters were also measured. Table VIII shows the number of aerosols re- weighed and the number of valves measured. No significant weight change was found in the recheck of the aerosol units filled to determine the effect of variables or the fill tolerances for the Propellant 142b/11 (50:50) systems. In the Propellant 12 study, several aerosol units checked for weight change showed a significant weight loss. This prompted a weight loss check on all the units filled and the subsequent elimination of approximately 10% of the units from the study. Water bath tests showed that the leakage occurred between the valve cup and the can bead, thereby indicating that a wider crimp diameter is required for high pressure Propellant 12 systems. The average weight loss rate of the population used in this study was found to be 0.5 mg/hour. Since most of the units were weighed within 5 hours from the time of manufacture, the average weight loss of the units analyzed was only 2.51 rag. The propellant fill levels for the Propellant 12 study were determined after a review of several published aerosol cosmerle and pharmaceutical formulas (4). To approximate these fill levels, a Continental Can Co. 202 X 214 container was found to contain 148 cm 3 of water at 21 øC with a Risdon Manufacturing Co. 6422 valve inserted. Assuming a 10%

UNDERCAP FILLER FOR AEROSOLS 381