SOCIETY OF COSMETIC CHEMISTS OF GREAT BRITAIN 47 10. Outline the factors which must be considered in selecting a preservative for a toilet preparation. 11. W'at are the important micro-organisms occurring on the skin ? Discuss the relative importance of each and the selection of a germicide which may be used to inhibit their development. SECTION E 12. Describe with appropriate diagrams the structure of human epidermis. 13. Define the term 'emulsifying agent'. Describe, with specific examples, the properties and uses of the principal classes of emulsifying agents. PAPER II (Monday, 29th June 1964.) Candidates should answer FIVE questions only one question from each section. Each answer must be commenced on a separate sheet of paper or book. Where possible, express relationships and reactions in equations with a full explanation of symbols used, and give simple sketches where appropriate. SECTION A 1. Describe the experimental set up and operation of a surface balance, commenting on some typical relationships between surface pressure and areas occupied by molecules of insoluble materials. When 1 x 10 -• cc of a certain gum (density 0.9 g/cc) was compressed on a surface balance at 19øC the following values of surface pressure were obtained. Area per molecule Surface pressure (A ø•) (dynes/cm) 2800 O. 10 2061 O. 15 1700 0.20 1480 0.25 1333 0.30 By making a suitable plot assuming the film is gaseous in nature and given that the Gas Constant (R)= 8.31 x 107 ergs/mole degree calculate the molecular weight of the gum.

, JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Explain what is meant by the "spreading coefficient." If the surface tension of water is 72.8 dynes/cm at 20øC, the surface tension of benzene is 28.9 and the interfacial tension between benzene and water is 35.0, what is the initial spreading coefficient ? Discuss the practical importance of wetting and spreading during the action of cosmetic preparations. SECTION B 3. Describe either the extraction and refining of fats and oils with refer- ence to those of cosmetic interest or a classification of the lipids indicating the uses of those of cosmetic interest. 4. Infra-red and ultra-violet absorption spectroscopy are of value for the identification of organic chemical substances, Write a short account of the physico-chemical principles upon which this statement is based. 5. What contribution would you expect chromatographic methods to make to the analysis of (1) an essential oil, (2) a fixed oil, and (3) a dyestuff ? Discuss the experimental procedure in one instance. SECTION C 6. Write short notes on what you know about six of the following perfumery raw materials Amyl cinnamic aldehyde Lavandin oil Citronellol The nitro musks Sandalwood oil East Indian Terpineol Lemongrass oil Linalyl acetate , (a) Suggest one simple formula of at least four constituents for each of the following types of floral perfume :- Lilac, violet, rose, and lavender Include if possible an approximate indication of the proportions of those constituents mentioned. (b) What factors need to be taken into account in formulating a perfume for a white toilet soap ? SECTION D 8. Discuss the limitations of the falling sphere method of measuring viscosity. A glass ball weight 0.157 g and 0.5 cm in diameter was allowed to