PROPELLENTS IN PRESSURIZED PACKAGING 355 able failures may result. Normally the valve mounting cup will crimp parallel to the highest point on the bed of the can or parallel to the high point on the flowed-in gasket. This design may be no disadvantage to a fluorinated hydrocarbon propellent system since the propellent may swell the gasket and effect a seal against further seepage. With nitrogen a noncontiguous and positive seal could be disastrous in prematurely ex- hausting the gas. To overcome this situation, crimpers should be engi- neered to incorporate spring-loaded balls creating a bearing surface over the entire circumference of the mounting cup and insuring a contiguous seat with the bead of the can. In addition, devices can be installed which are sensitive to pressure and volume changes in the line and can be hooked up in an electronic relay circuit to identify or reject those containers not receiving their full charge of gas. Crimp pry testers are available which effectively test the seal between the valve mounting cup and can. 6. Contamination For the most part the product within the container is usually free of bacterial contamination or can be made so by the incorporation of suitable preservatives or resorting to pasteurization and sterilization techniques. A major problem which must be evaluated is the microbiological contamina- tion by air-borne bacterial and fungal populations in the dispensing spouts between usage. FUTURE DEVELOPMENTS AND POTENTIALS An extremely exciting development which promises to be a great stimu- lant to all types of aerosol packaging is to be found in the metered valve principle described by Urlaub in U.S. Patent No. 2,778,543. This patent involves the use of a floating ball check valve in the dip tube and can be regulated to meter volumes from fractions of a cubic centimeter to well over an ounce, depending on such factors as the length and diameter of the dip tube, the specific gravity of the ball, the diameter of the ball in relation to the diameter of the dip tube, and the specific gravity and viscosity of the bulk. This particular concept is applicable to products both under inert atmospheres and liquefied propellent systems. The packaging of cough mixtures, vitamins and nasal sprays under nitrogen is imminent with metered dispensing. Other fruitful areas for exploitation of metered dis- pensing are dishwashing detergents and alcoholic beverages. The latter case would have the added advantage of making the bottle tamperproof and nonreusable. An additional patent defined as a metering device controlling discharges of fluids from aerosol containers was issued to Stetz et al. under U.S. Patent No. 2,815,889. This patent involves the use of a porous plug fitting tightly into a chamber within the dip tube at a predetermined dis-

356 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS tance from the valve. This porous element measurably retards the flow of the liquid under internal pressure, and upon each opening of the valve the charge accumulated above the plug may be dispensed. Because of the impeding action on the flow of material, a time interval is required to refill the space in the chamber between plug and valve. It would appear that the limiting factors in respect to this patent are the viscosity of the fluid and the time element involved in filling the metering chamber. PRODUCT POTENTIAL Productwise there are many areas for exploitation utilizing the concept of pressurized packaging under inert atmospheres. In the proprietary drug field we may cite, to name a few, such products as eye drops in a drop dispensing assembly, antacid preparations such as milk of magnesia or the more modern suspensions based on magnesia trisilicate, aluminum hy- droxide and bismuth salts. In the ethical pharmaceutical field many applications come to mind. For example, a recent study concerns the treatment of odds externa with a suspension of oxytetracycline and hydrocortisone. Sixty-eight per cent of the infected ears were rapidly and completely cleared and there was im- provement in 94 per cent of the patients. Excellent relief from pruritus and pain was obtained in almost every case. The topical antibiotic steroid therapy reported here was judged to be a superior method of treatment of commonly occurring external otic infections. A pressurized package containing hydrocortisone and oxytetracycline would enhance the stability, particularly of the antibiotic, since the package would be hermetically sealed from the point of manufacture and at no time would be open and exposed to the atmosphere. A novel and practical conception in the topical anti-infective field is a PVP/iodine complex product currently being readied for marketing at the physicians' level. This product is packaged in glass and is sprayed on the skin to provide a broad spectrum antiseptic in a convenient, easy-to- use form. The product has prolonged germicidal action, is nonirritating, film-forming and nonstaining, In the cosmetic field, hand lotions, bubble baths, shampoos, hair prod- ucts and soft creams, are all adaptable to inert gas pressure packaging. These products have viscosities that can best be served in nitrogen pres- surized containers. Deodorant and antiperspirant preparations offer a special problem. Now being packaged under refrigerant type propel- lents they have not succeeded as well as they should have because of the somewhat uncomfortable cooling effect of the spray. The cooling effect could be eliminated by using nitrogen as the propellent. However, the drying quality and spray pattern of the nitrogen package would have to be improved to win consumer acceptance. Imminent valve developments