PERFUMES IN PRESSURIZED PRODUCTS 235 introduction of hydrochloric acid are magnified by traces of metal even if the metal is present only in the perfumery constituents. The • problems which arise in producing a stable perfume for use in metal containers in the presence of trichlorofluoromethane are great and, without a doubt, many of our normal ingredients are quite unsuitable for this type of product. Supposing we packed in glass an existing handkerchief perfume under the most favourable of pressurized conditions, say, Per cent Alcohol 47.5 Dichlorotetrafluoroethane 47.5 Perfume 5.0 If we are concerned with smelling the perfume only from a surface, then what would be its stability compared to its equivalent in the non-pressurized bottle ? While the answer well differs from perfume to perfume, in the main, there will not be a great difference between the two types of packaging. After one year the pressure packed perfumes seem to take on a rather sharp ester-like note and in some cases terpenes tend to produce "off" odours. One other effect is the formation of an acetal odour. This latter effect (the production of diethyl acetal of acetaldehyde) undoubtedly occurs in the presence of alcohol and easily hydrolysed propellants. [Received: l•lth October 19581 DISCUSSION DR. B. L. RAo: Can gums and resins be used as fixatives for perfumes in aerosols ? THE LECTURER: The resins may be used for their odour and fixative properties just as in normal types of perfumes. The question of valve clog- ging has been somewhat over-emphasized. Nevertheless, it is a wise pre- caution to use resins which have been extracted with special solvents. DR. B. L. RAo: May crystalline materials be used in aerosol perfumes ? THE LECTURER: Yes. The question of solubility must be solved as with a normal alcoholic perfume. In other words, the perfume containing the crystalline ingredients must be tested in the presence of both alcohol and propellant to ensure that no precipitation takes place on standing.

236 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS A METHOD FOR STUDYING THE STATIC ELECTRICITY PRODUCED ON HAIR BY COMBING R. G. BARBER and A.M. POSNER, B.Sc., Ph.D.* A detailed descrilffion o5 •e appara•s is given and the accuracy and SCOl•e of the method are illustrated. A NUMBER of methods have been described for studying the magnitude of the static electricity produced by combing tresses of hair and single fibres after treatment with various materials •-5. They all suffer from the disad- vantage of being complex and relatively insensitive to small differences resulting from different treatments. This paper describes a new method for studying the charge produced on hair as a result of combing the hair with a comb made from a material dissimilar to the hair itself. The method is both simple and effective and allows a quick comparison to be made of the effect of various treatments on the magnitude of the static charge, and other things being equal, the effect on "fly-away". The results obtained with this apparatus have been shown to correlate very well with observations made independently in actual practice in the hairdressing salon. The method is based on the fact that the charge produced on the hair is equal though opposite in sign to that produced on the comb. The distance at which a freely suspended strip of gold leaf commences to be attracted towards the comb is measured, and the magnitude of the charge is then a simple function of this distance. The following gives a detailed description of the apparatus together with some of the results, which illustrate the accuracy and scope of the method. iExPERIMENTAL The static electricity produced on hair is primarily dependent on the relative humidity of the ambient atmosphere, and it was therefore necessary to generate and measure the charge in an atmosphere of known and con- trollable humidity. This was done by enclosing the essential parts of the apparatus in a large glass tank, the open side of which was covered with a thin Perspex sheet. * County Laboratories, Ltd., Startmore, Middx.