142 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the samples, proximity of the samples in space and time, etc., also have a marked effect. Tolerances for the colour of signal glasses have been laid down, but in some industries, e.g., the dyeing industry, the precision of matching is very high indeed, and the specification of tolerances would be difficult. The application of colour science to cosmetics includes the colour specifi- cation of the cosmetics, colour control in their production, the limitation in the number of different colours of a given product that could be distin- guished by the customer, the effect of fluorescent lighting on the colour rendering of complexions, and the possibility of producing cosmetics which are colour stable under different illuminations. Talking of Perfumes Again* By J. PICKTHALL, F.R.I.C. MR. PICKTHALL INTRODUCED his talk by stating his aims. These were to introduce Perfumery to those who knew it only by name, to assist those with a working knowledge, and to interest the experts. Lack of alphabet and descriptive words make discussion of Perfumery very difficult. Such words as top or back notes, light and heavy notes, and warmth of odour are sadly lacking in descriptive properties, even be- tween experts, while to employ chemical terminology, e.g., aromatic alde- hydic or phenolic, is not much better, considering the number of organic chemicals which qualify for the description "aromatic." An improvement occurs when flower names are used, e.g., Lavender, Rose and Carnation, even though the use is restricted to a relatively few well- known types. ODOUR PERCEPTION The nose, unlike the eye and ear, can receive and identify an apparently unlimited number of different odours. It has been suggested that the essential step in odour perception may be the contact of molecules with the thousands of hairs present in the sensory cells of the olfactory cleft and the surface layer of mucus and water. TR^ImN• A PERFraMER Long and arduous practice and patience are essential for a perfmner. The first step is to learn the odours of certain standard oils, and to be able to recognise them whenever they occur. * Presented at the March 5, 1954, Meeting, London.

THE BRITISH SOCIETY OF COSMETIC CHEMISTS 143 IMITATING A PERFUME One of the finest training techniques is the matching or imitation of an existing perfume. Following this comes the use of the back of the hand as a steam distilla- tion unit by rubbing the perfume on to it. UsE OF FINISHED PERFUMES A simple Lavender perfume could be made to the following formula Lavender Oil 40/42 .......................... 89.5% Bergamot Oil ............................... 10.0% Musk Ketone ............................... 0.5% As a perfume for a toilet water this would be regarded as acceptable, but in powders, lotions and creams, the perfume would be fugitive, with a tend- ency to become stale, while if used in soap it would be a dismal failure. A reasonable soap perfume might be obtained by using lavandin, lavandin and lavender concretes and spike, modifying the ester notes by use of linalyl, terpinyl and bornyl acetate, and the alcohol notes by use of terpin- col and borneok Oakmoss, labdanum, and musks could be added to assure adequate back notes and fixation and generally sweeten the whole accord. FIXATION This is simply a retarding of the rate of evaporation of the constituents of a mixture of volatile substances. Fixative effects may be present by virtue of the composition of a blend, for example, by dilution phenomena, or by Chemical blending, e.g., forma- tion of hemiacetals between aldehydes and alcohols, and Schiff's bases from aldehydes and amines. If the chemical aspects of molecular attraction are considered it would appear to indicate that certain hydrogen bonding effects would explain the very good fixative properties of benzyl benzoate. It is possible, of course, to obtain fixative effects with non-polar materials, such as paraffin wax, but although such a material might bring about the effect by solid solution, hydrogen bonding phenomena cannot be entirely ignored.