JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS odour have been put forward and, in the main, they can be divided into two classes--the chemical or corpuscular and the physical. The latter school of thought suggests that odorous substances radiate high frequency vibrations and that differences in wave-length are responsible for differences in odour. To some extent these ideas were founded on the false assumption that certain chemicals emitted odour for long periods of time without loss in weight. Thus natural and synthetic musks were said to be capable of transferring their odour to grease-smeared surfaces without weight loss, when exposed to the atmosphere. These experiments reflect upon the inadequacies of our weigh- ing equipment, although one must bear in mind that 1 gm. of Musk Ambrette is theoretically capable of releasing 2.7 x 102• molecules, and that one "sniff" will bring odour response when as little as 0.00000000025 gms. of natural musks are present in the air and, perhaps, ten times this amount of synthetic musk. I was rather intrigued with the little item from February International Perfumer. This note mentions Eugene Rimmel's extraction of odorous materials from petals by means of volatile solvents and is a quotation from his book, written nearly 100 years ago. Mentioning that the process had not been put to any practical application on account of expenses, he finishes as follows: "It has, however, served to prove the imponderability of fragrant mole- cules, for although this substance from its high state of concentration appears at first sight to be the solidified principle of scent, after it be treated several times with alcohol, it gradually loses all its perfume, and yet the residue is not found to have lost one atom of its weight." I think we can accept the fact that odorous substances release molecules which are air-borne to the nose and that with some substances a quick intake of breath or "sniff" is required to provide the necessary concentration of molecules to evoke odour response. E. D. Adrian writes effectively on the subject in his "Flavour Assess- ment" in Chemistry and Industry, November 28, 1953, and describes how the essential step in odour perception may be the contact of molecules with the millions of hairs present in the sensory cells of the olfactory cleft and the surface layer of mucus and water. Just as we can accept volatility as an essential property, so we can include relative solubility in water and lipides. In fact, I like to think of an odorous molecule as a kind of emulsifier, its effect and performance depending upon its ability to overcome tension between surfaces and its relative affinity for aqueous and "oil" phases. This "fixing" of the molecule at the surface or interface could determine the setting of the angles bonding the atoms of the molecule, changes in the bonding angles setting up variations in potential energy. Just how the released energy is transmitted and analysed is another matter. To me the whole mechanism has something of the Hollarith punch-card system. 184

TALKING OF PERFUMES AGAIN Information in the form of molecules is fed to the nose where it is fixed via its relative solubility at the interface. Here it takes on a penetrative shape determined by the bonding angles. Electric charges are allowed to pass through the "punched card" and proceed to the olfactory receptors which relay the appropriate message to the brain. It is quite beyond me to enlarge on these vague and unhelpful ideas. DEFINITION I have elsewhere suggested that perfumery may be defined as the art of producing or creating a pleasant impression by blending some or many odours and that a simple mixing of odoriferous ingredients may not necessarily pro- duce a harmonious effect. Despite the efforts of certain modern "artists," perfection of subject-matter is the art of the painter and sculptor, and the value of his work may be iudged by all with eyes to see. Music and perfum- ery are less tangible to the senses and consequently less easy to define anG appreciate. With music, a "mixture" of notes may or may not produce' harmony to the ear the skill of the arranger and dispenser will determine' this point. Even in this case only the expert can critically judge the quality of a piece of music and the way in which it is presented. In much the same way we can arrange our odour notes and present them for the approval of the nose, and whilst the expert will obviously be capable of a more critical examination, the individual, as with music, "knows what he likes." It is almost as easy to strike the wrong note in perfumery as in music, although, thankfully, I say less people will be aware of the fact. TRAINING Are perfumers made or born ? I suppose each successful perfumer must "have it in him," but, as in all walks of life, long and arduous practice is the keynote to success. There are so many thousands of ingredients to consider and so many ways in which to use them. Perhaps consideration of the training of a perfumer would offer an introduction to his ultimate require- ments. Unfortunately, there are no organised schools of perfumery and no accepted curriculum. One can only indicate the methods one would person- ally adopt or recomlnend. Let us assume that the trainee starts with a reasonable knowledge of chemistry, particularly organic chemistry--that is the chemistry of the carbon compounds which comprise the raw materials with which he will work. For the moment he is not concerned with theories or physics, but with becoming familiar with his perfumery ingredients. What have we to offer our hopeful by way of vocabulary ? Precious little which will help him. Classifications have been made and whilst perfumers in general can understand each other to a certain extent, no two people appear to agree on all points. It will be necessary to show him a selected number of important ingredients those essential oils or synthetics in most common 185