JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS PERFUMERY CHEMICALS R. A. S. LACEY, A.R.I.C.* A lecture delivered before the Society on 17th December 1958. The l•urity of l•er•umery chemicals is discussed, and illustrated by means of a number of chromatograms. The influence of various "impurities" on odour is also dealt with. INTRODUCTION IN INX)USTRmS of all kinds the accent is on development in the form of improved and new manufacturing techniques. In particular, this is true of the industry which produces perfumery chemicals. Equipment now in operation is far in advance of that of even a few years ago, and is responsible for a much higher through-put, closer control and superior operating con- ditions. This satisfactory state of affairs is due to improved instrumentation and progress in chemical engineering, coupled with new techniques and greater know-how. In addition, new methods of testing and controlling the products during and after manufacture have become available and these enable the fullest advantage to be taken of improved manufacturing pro- cesses. Finally, a number of new starting materials have become available to the manufacturer during the last few years. As a result of these changes, new odorous chemicals are being produced, but of even more importance, we are offered the opportunity to raise the general standard of a large proportion of the perfumery chemicals which have been known for years. It is here that the manufacturer turns to the perfumer for guidance. Krajkeman x gave you an excellent review of the difficulties of this subject and I am sure he will be the first to acknowledge the fact that, even in the short space of two years, a considerable amount of water has passed under the bridge. There is plenty of evidence to show that many perfumers are conscious of these new possibilities and eager to take advantage of them. So that maximum advantage may be derived from the recent developments, it is necessary for the perfumer to become more fully aware of the nature of his raw materials. The manner in which the perfumer tackles the problem of obtaining better perfumery chemicals is of paramount importance, and the more clearly he understands and states what it is he requires, the sooner will he be satisfied, and furthermore, less of his time will be wasted examining a large number of uninteresting sub- stances. * Polak & Schwarz (England), Ltd., Haverhill, Suffolk.

PERFUMERY CHEMICALS 3 THE PERFUMER'S REQUIREMENTS All the foregoing may seem obvious on the one hand, and perhaps difficult to achieve on the other, but on further consideration it becomes clear that much time could be saved by a little thought. As an example of this, one of the most difficult requests met with by a supplier is for a purer or maybe even a pure perfumery chemical. Ignoring the point that in practice there is no such thing as a pure substance, the difficulty with this request is not in producing the material, but in ascertaining what it is the customer really requires. Maybe his desire is actually for a purer product, but, as will be shown later, with many of our products this is not the case and it is then that we are faced with the fact that the removal of minor constituents from the product may increase the price out of all proportion and also frequently result in a product with an uninteresting odour or one which is unsuitable for the purpose in mind. It is easy to understand how this request has originated. The existing material has been found unsatisfactory because it has a crude or unpleasant note or it may be that it is satisfactory by itself, but that the resulting perfume in which it is incorporated lacks desirable characteristics such as a fine, clean note. The perfumer, by his art and instinct, senses that certain by-odours in one or other of his raw materials have combined and are accentuating each other to give this effect. Obviously, this results in a desire for a higher quality perfumery chemical and the word "pure" has a fine ring to it, but bewares-- both the words "pure" and "impurities" should be used with the greatest care. I am reminded of an instance when visiting an exhibition: I called at the stand of one chemical manufacturer and asked whether he could supply a certain chemical. He was most enthusiastic and we had discussed it for some time when we got to the point when he enquired as to the purpose for which it was to be used. When he was told for perfumery, his face dropped and his enthusiasm vanished. He explained that he had had many unhappy experiences when dealing with perfumers in particular, he quoted a case where he submitted many samples, all of which were rejected as unsuitable on the grounds of the quality of their odour. He finally requested a sample of the material which the customer considered was suitable. When he tested this in his laboratory, he found that it contained less than 95 per cent of the active ingredient, whereas his later samples had all been better than 99 per cent pure. At this he gave up. By the way, I never received a sample of the material in which I was interested. \Vithout attempting to define the term "perfumery chemical", let us discuss the group generally and examine some of the members in detail to obtain a better understanding of this important class of compounds. The materials in this category range from chemicals of known composition