636 JOURNAL dF THE SOCIETY OF COSMETIC CHEMISTS DR. B. A. SCOTT: IS the chemical nature of these lanolin derivatives sufficiently well defined to assess cross-sectional diameters ? If this is the case, plotting per cent weight of additives rather than fraction of surface covered at any concentration may explain differences between lanolin derivatives. MR. CONRAD: The materials listed cover a cross-section of all types of lanolin derivatives. Some of these are esters, some are extracts of alcohols containing hydrocarbons, some of them are acetates of alcohols. There is a range of molecular weight, lanolin itself being anywhere from 700 to 1000 depending on the presence of diesters. Some of the lower weight esters are around 350. You have a difference in molecular weight, you have quite a difference in viscosity, and you have quite a difference in consistency. These are all factors, there is no question about it. Here we are trying to present a general method for comparative use in wetting. Mr. J. G. PITT: I would have thought that the wetting effect of these lanolin derivatives would be proportional to concentration in the vehicle rather than relative to the weight of powder. When the flow point test is done and a dispersed suspension obtained, does the powder reflocculate when the full dilution with vehicle is carried out ? MR. CONRAD: We tried this in one or two cases, but it seemed to be a concentration effect. A minimum critical concentration of additive is probably required to prevent reflocculation.

BRITISH CHEMICAL REFERENCE SUBSTANCES In late 1963, the General Medical Council and the Pharmaceutical Society of Great Britain agreed to set up a joint authority to prepare and distribute chemical reference substances needed to carry out certain tests and assays described in the British Pharmacopoeia, the British Pharmaceutical Codex and the British Veterinary Codex. The Joint Committee held its first rneeting in March 1964, and established a number of panels. Each panel was charged with the task of establishing one or more of these reference substances, and, since these substances might be of value for other purposes, the panels were asked, should it prove impracticable to obtain absolute purity, to ascertain as far as possible the amounts of all impurities. The first two British Chemical Reference Substances are now available- Digoxin and 2-t-butyl-4-methoxyphenol (the most active isomer present in butylated hydroxy- anisole). The 2-t-butyl-4-methoxyphenol Reference Substance is required for the assay of butylated hydroxyanisole and in the IR identification test. In this case, a purity of at least 99.85 per cent has been achieved, the balance being made up of very small amounts of 3,8'-di-(t-butyl)-2,2'-dihydroxy-5,5'-dimethoxybiphenyl (bis-BHA), 2,5-di(t-butyl)-4-methoxyphenol, 4-methoxyphenol and a trace of an unidentified impurity. As well as its pharmaceutical uses, butylated hydroxyanisole has extensive usage in the food industry as an antioxidant in oils and fats, and the establishment of this reference substance may be welcomed in fields outside of pharmacy. Samples of these reference substances are distributed by the Pharmaceutical Society and are available on application to the Assistant Director, Department of Pharmaceutical Sciences, 17 Bloomsbury Square, London, W.C.1, at a cost of • for 0.2 g of the 2-t-butyl-4-methoxyphenol. 2-t-BUTYL-4-METHOXYPHENOL The batch of 2-t-butyl-4-methoxyphenol constituting the Reference Substance was prepared for the Joint Committee by May and Baker Ltd. from commercial material of good quality by fractional distillation in vacuo, followed by passage of a solution in chloroform through alumina and removal of the solvent from the eluate. The Reference Substance has the following general analytical characteristics: Description: A slightly cream-coloured crystalline powder with a characteristic odour. Sulphated ash: Less than 0.05 per cent. Volatile impurities (determined as the loss in weight in a partial vacuum for • hours): Less than 0.01 per cent. Melting-point: 64.1 o Thin-layer chromatographic test (British Pharmacopoeia 196•, Addendum 1964): No spots detectable other than that due to 2-t-butyl-4-methoxy- phenol. Infra-red spectrum (British Pharmacopoeia 1963, Addendum 1964): Complies with test. Ultra-violet spectrum: In a mixture of 49 parts by volume of dehydrated alcohol, B.P., and 1 part by volume of N hydrochloric acid, a 0.002 per cent w/v solution shows maxima at 228 mp (El per cent, 1 cm=340) and 292 mp (E 1 per cent, 1 cm=205) and a minimum at 253 mp (El per cent, 1 cm=8)• 637