256 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS T.•SLZ 2--"REo. ux•-ED HLB" VALVES w/o o/w Emulsion Emulsion Solubilizing* Acid, stearic .. 17 Alcohol, cetyl 13 Lanolin, anhydrous }' 15 Oil Cottonseed .. 7.5 Essential Mineral, heavy ¾ 1•)'. • Mineral, light 4 10-12 Vitamin (with fats or oils) ..... Vitamin (fat free) Petrolatum ¾ lb'.'5 Vitamins Esters ..... Oils (see "Oils" above) Wax Beeswax 5 10-16 Microcrystalline 9.5 Paraffin (household) ¾ 9 1• '.• 1¾.5 15 16.5 * O/W, i.e., solubilizing in water. terials used with surfactants, a cross relationship could be set up. With such a system, it should be possible to screen all the available surfactants in a few minutes and select a few that are worthy of extensive study. In summary, two conditions usually must be satisfied in choosing a sur- factant for any desired formulation. First, the proper HLB or hydrophilic content of the surfactant must be used, and second the proper chemical type of the surfactant must be chosen. Random choice, i.e., the old trial- and-error method, can lead to many selections that are wrong in two ways that is, both by chemical type and HLB. By first determining the optimum HLB value and then selecting and testing a variety of chemical types at this particular value a large number of wrong trials can be eliminated. The HLB method permits a more systematized trial than possible previously. HLB values may be calculated from analytical or composition data or the system may be used without calculating or determining exact value since it is a method of operation that has some correlation with water solubility of the surfactants. There is need for further work in this field to establish a rapid, more exact experimental procedure for observing HLB values, for de- termining "required HLB's," and for classifying and correlating chemical types of surfactants.

ACCELERATED STORAGE TESTS* By F. GROSSMITH, B.Sc., F.R.I.C. Macleans, Ltd., Brentford, Middlesex, England Is SPEAKING of accelerated storage tests one has in mind procedures which w•11 give a rapid indication of the shelf life characteristics of cosmetic preparations. Possible types of deterioration cover a wide field, and in- formation may be required covering some, or all of the following character- istics: emulsion stability freedom from phase separation or other change in structure of the prod- uct colour stability freedom from clouding and deposition resistance to spoilage by microbiological or oxidative processes avoidance of drying out freedom from undesirable corrosive action between product and con- tainer etc., etc. AVAILABLE TECHNIQUES--ACCELERATED SHELF TESTS At the outset let it be said that there is no complete substitute for the long term shelf test under practical conditions through a range of seasons, and for the new product, whenever the possibility exists, such tests should be carried out. Next to long term shelf tests are shelf tests involving an intensification of the environmental factor of interest, for example, high humidity, ultraviolet radiation, exposure of the unit pack to the vapour of odorous materials, and, perhaps most important of all, testing the stability of the preparation when exposed to variations of temperature. During practical conditions of transit and storage, products are exposed to temperatures which are rarely static for long, and so temperature tests should include alternating temperatures. It is usually accepted that twelve-hour cycles alternating between -3-2 and 50øC. duplicate the effects of most temperature extremes. For the home market 30øC. alternating * Presented at the April 9, 1954, Meeting, London, England. 257