THE BRITISH SOCIETY OF COSMETIC CHEMISTS THr, TWO LECTURES given this year before members of the Society are summarized below. The meetings were held at the Royal Society of Tropical Medicine and Hygiene, in London. The full texts will be pub- lished in later issues of the JOLTR•r^I,. Colour and Colour Vision* By PROFESSOR W. D. WRmHT THE COLOUR or A surface is determined physically by its spectral reflection, but while the appearance of a surface can be roughly assessed in this way, knowing the colours in the spectrum, account must be taken of the way the eye integrates the different parts of the spectrum reflected by a surface. Colour matching experiments strongly suggest that there are three types of colour sensitive receptors in the retina, and an international system of colour measurement has been established on the basis of three- colour mixture and matching. Colour is thus produced (a) by a light stimulus having some particular spectral composition, (b) by the reaction of the light with the retinal re- ceptors and (c) by the reaction in the brain caused by the signals from the retina. The colour perceived may be modified by changes in the state of adaptation of the observer's eyes or by the contrast conditions, even though the light stimulus is unchanged. Under some conditions, adaptation can largely compensate for changes in quality of illumination, e.g., between tungsten lighting and daylight, so that many familiar objects exhibit a marked degree of colour constancy with change in the lighting. Some coloured materials, however, and especially those with a high reflection band at the far red end of the spectrum, exhibit striking colour changes. The colour rendering of fluorescent lamps poses a special problem on account of the presence of the mercury lines in its spectrum, accompanied, very often, by a deficiency of energy at the red end of the spectrum. The ability to discriminate colours varies to some extent from one ob- server to another and is particularly poor with persons having defective colour vision. The observing conditions, e.g., illumination level, area of * Presented at the February 5, 1954, Meeting, London. 141

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.