ON PURCHASING ESSENTIAL OILS A chemical examination is, of course, a necessity, but it should be looked upon rather as a diagnosis rather than a final verdict. To a chemist unaccus- tomed to evaluating these products there are special peculiarities he will find that are a little removed from ordinary routine analysis. There are several reference books which give details of the special methods employed in this field, and one may name amongst others Guenther, "The Essential Oils," Volume I Simon-Thomas, "Laboratoriumsbuch fiir die Industrie der Riechstoffe, 4-5 Auflage" British Standard No. 2073: 1953, "Methods of Testing Essential Oils," "Methodes et Constantes Analytiques des Huiles Essentielles," issued by the Syndicat National des Fabrica•ts et Importa- teurs d'Huiles Essentielles oi Grasse the methods of the Scientific Section of the Essential Oil Association of the United States of America the various pharmacopceias such as the B.P. 1953, the B.P. Codex 1954, and the U.S.P. XIV. Having determined the various.physical and chemical characters, the literature will have to be consulted to see if the values found for the sample of essential oil falls within the usually accepted limits as given by Gildemeister and Hoffmann, "Die •ltherische Ole," 3rd edition Guenther, "The Essential Oils," Volumes 1-6 Parry, "The Essential Oils" "The Handbook of Standards" issued from Grasse, and the Standards issued by the Essential Oil Association of U.S.A. (both mentioned previously) while a very concise and authoritative summary of all aspects of essential oils is given in the section on Huiles Essentielles, by Y. R. •aves, in "Traite de Chimie Organ- ique," Tome XVI, by Grignard, Dupont et Locquin. Tests for possible additions and adulterations can also be carried out. While the results of the analysis may lead to some samples being rejected, there will be several samples that will pass this first stage of the examination, and here again it must be stressed that the deciding test will be an olfactory or taste test. This test is adapted to the use to which the oil is intended. With oil intended for the beverage trade, the sample should be made into a soluble essence by shaking one volume with four volumes of 70 per cent ethyl alcohol and using the resulting lower layer at the rate of 1 to 2 ounces to a gallon of mineral water_syrup (6 lb. of sugar in a gallon of syrup acidified with 2 ounces of citric acid per g•llon) and diluting the resulting syrup with water at the rate of 1« ounces of syrup up to half-pint with plain or aerated water. If the oil is intended for the confectionery trade it can be tested in Iondant at a rate of 1 in 10,000, or if the oil is intended for high boilings a small batch of boiled sweets should be made in the laboratory to see that the oil reacts favourably to heat treatment. Similarly for the flour confectionery trade a small cake or some biscuits should be made, baking to the same temperature at which the oil is eventually intended to be used. 261

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Where the odour of the oil is of critical importance as in the perfumery and cosmetic trades it should be tested on smelling strips at intervals, taking particular care to examine the residual odour carefully. A good way of also testing the odour is to place 50 mi. of water in a 250 mi. conical flask, add a drop or two of the oil and then well swill the flask. The odour of the oil should then be observed in a similar manner to a brandy connoisseur evaluating the aroma of his favourite beverage. The chemical analysis can reveal many interesting points if careful scrutiny be made of it and the various characteristics taken in conjunction with one another. Such points as a high non-volatile residue, a particularly low or high specific gravity, an especially high optical rotation, an abnormal peroxide value can all indicate certain facts regarding the origin and age of the oil, and in some cases may allow a further grading to be carried out. Having by the procedure given above reduced the choice of samples to those from which the final choice will be made, it will probably be found that there are one, two or maybe three samples left for the final decision. The deciding factor will now rest on the price and the behaviour in the finished product. A small batch of the final product in which it is intended to incor- porate the essential oil is made under identically the same conditions and using the same constituents as standard works batches, and compared with the standard product for aroma or flavour. Having carried out all of these tests it is then that the price factor has to be taken into account. It is a fatal mistake to buy the cheapest essential oil unless critical tests have proved that it has the covering power and tenacity of the others. Price should be the last sorting out factor instead of, as in many cases, the first one. Another point to which attention should be drawn is that in any case the B.P. and B.P.C. are the minimum standards that an oil has to comply with, and also that they are standards for oils which are intended to be used for medicinal products and that the quality that would satisfy these require- ments need not necessarily be the quality that is suitable for other purposes. Having made the final judgment and having decided to buy one of the samples submitted, and having forwarded the order to the merchant or essential oil house, one will then have to check the delivery against the sample. Here a few general words regarding sampling will not be out of place, as sometimes arguments arise on this point. It sometimes happens that the original sample submitted is a type sample and that on buying the bulk there may be very slight differences in the delivery. There are reasons for this. It may happen that at the docks only one or two of the original containers have been opened, as many buyers of essential oils lay great stress on having the oil in original containers, with an unbroken seal carrying a well-known producer's name on it. As the oil is the result of several different distillations and these have to be blended, the lack of a very large capacity 262