286 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The ratio of propellent to solvent does not appear to be a controlling factor. Thus, as shown in Table 8, "12"/odorless mineral spirits/water emulsions with 40/20/40 ratios were nonflammable whereas those with a 60/30/10 ratio were flammable. In both cases the propellent/solvent ratio is the same. This is also shown in Table 9 where the "12"/"11" (30/70)/odorless mineral spirits/water emulsion with the composition ratio of 60/20/20 was flammable but the emulsion with the lower pro- pellent/solvent ratio of 40/20/40 was nonflammable. The spray characteristics appear to play a role in determining the flammability of the product. In Table 9, the "12"/"11" (30/70)/odorless mineral spirits/water emulsion with the composition ratio of 50/40/10 was non flammable in spite of the high concentration of solvent. This product had a very wet spray with the standard actuator. On the other hand, the emulsion with a 60/30/10 ratio was flammable with the lesser concentration of solvent. Changing the valve actuator from a standard actuator to a mechanical break-up type in some cases may shift a product that is flammable by the TABLE 8 FLAMMABILITY OF PROPELLENT "12"/ODoRLESS MINERAL SPIRITS/WATER EMULSXO•S Propellent/ OMS/Water Ratio • , Flammability , • Standard Actuator --• ----Mechanical Break-tm-• Flame Ext. Flame Sust. Flame Ext. Flame Sust. 60/20/20 NF* NF NF NF 40/20/40 NF NF NF NF 20/20/60 NF NF NF NF 60/30/10 FI. NF NF Fl. 40/30/30 FL NF NF FL 20/30/50 FL NF NF NF 50/40/10 FL FL FL FL 40/40/20 FL FL NF FL 20/40/40 FL NF NF FI. 2 parts Emcol 14/102 parts emulsion * NF, nonflammable FL, flammable. TABLE 9 FLAMMABILITY OF PROPELLENTS "12"/"11" (30/70)/ODoRI,ESS MINERAl, SPIRITs/WATER EMULSIONS Propellent/ OMS/Water Ratio 60/15/25 6o/2o/2o 40/20/40 60/30/10 40/30/30 5o/4o/lo 40/40/20 Flammability • Standard Actuator .... Mechanical Break-up• Flame Ext. Flame Sust. Flame Ext. Flame Sust. NF* NF NF NF FI. NF NF NF NF NF NF NF FI. FL NF NF NF--Stream NF NF NF NF Very wet NF NF NF NF Stream NF NF NF 2 parts Emcol 14/102 parts emulsion * NF, nonflammable FL, flammable.

AEROSOL EMUI,SION SYSTEMS 287 flame extension test into the nonflammable class by widening the angle of spray. This may also convert a product that does not sustain a flame into one that does, probably by better aeration of the sprayed material. Po/en/ia/ •/pp/ica/ions of the lVa/cr-i,-Oi/ Emulsions Thc water-in-oil cn•ulsion systclns that have been prcsc•tcd are obviously basic formulations. By the addition of suitable active ingredients, formula- tions with practical applications will be developed. The active ingredients do not necessarily have to be soluble in the aqueous phase. Organic soluble materials can be dissolved in the auxiliary solvent and water alone added if an emulsion type is desired. Also, organic soluble and water- soluble active ingredients can be combined in the same formulation by dissolving the former in the auxiliary solvent and the latter in the aqueous phase. As discussed in the previous sections, the spray characteristics of the emulsion systems can be varied from very fine to very wet by suitable choice of the emulsion system. This wide range of available spray charac- teristics provides a variety of potential applications from topical products, such as antiseptics, antiperspirants, etc., where a wet spray is desired, to room deodorant and sanitizer sprays, where a fine mist is necessary. In formulating, factors such as the type of container to be used, the pressure of the systems, type of spray, flammability, emulsion stability, and corrosion must all be considered. For many products, such as sun tan sprays, a water-in-oil emulsion system with an auxiliary solvent is par- ticularly desirable since it adheres to the skin and is not readily removed by water. In other cases, where contact of the aqueous phase with the skin is desired, a high boiling organic solvent is not desirable and an emulsion prepared without an auxiliary solvent or with a lower boiling auxiliary solvent, such as propellent "113" would be preferred. Most of the emulsion sprays, particularly those with auxiliary solvents, do not have an undesirable chilling effect on the skin. This is a consider- able advantage for topical applications. In most cases, redispersion of the creamed aqueous layer occurs with ease. In some cases, particularly where the viscosity of the emulsion is high, redispersion takes place in the aerosol container but not in the stand- pipe. When this occurs, the initial spray consists of an aqueous stream followed by the normal spray. This is undesirable and it is generally necessary to reformulate the product. Of course, if the container is used in an inverted position without a standpipe, the problem does not exist. EXPERIMENTAL Preparation of Emulsions The method of preparation of the various emulsions depended upon the