TECHNIQUES FOR ASSESSING RHEOLOGICAL PROPERTIES years ago someone tried to calculate the shearing forces involved in certain elementary operations, such as pouring a liquid or a non-Newtonian fluid out of a bottle or extruding it from a syringe, just to get some idea of the shearing conditions which should be applied in viscosity measurements, but to date no one has gone any further than this.

J. Soc. Cosmetic Chemists 17 467492 (1966) ¸ 1966 Society of Cosmetic Chemists of Great Britain Thin-layer chromatographic techniques in residue analysis J. THOMSON and D.C. ABBOTT* Presented at the Symposium on "Physical Methods," organised by the Society of Cosmetic Chemists of Great Britain, at Bristol on I6th November 1965. $ynOl•Sis--Thin-layer chromatography has rapidly developed into a precise technique of considerable use to the residue analyst. This paper attempts to deal succinctly with all aspects of thin-layer chromatography, from the choice of the adsorbent to the final docu- mentation of the developed plate. Recent advances in thin-layer chromatography, wedge- layer, multi-band layer and gradient-layer chromatography are also covered by the paper. INTRODUCTION The introduction of paper chromatography by Consden, Gordon and Martin (1) as an extension of the partition chromatographic technique of Martin and Synge {2) was followed by a very rapid expansion of the use of these procedures. The advantages of paper chromatography in partic- ular, e.g. small sample size, excellent resolution and short times involved, over earlier separatory methods were so great that the accompanying disadvantages tended to be overlooked. While being admirably suitable for amino-acids and hydrophilic compounds in general, many difficulties arose when lipophilic compounds were studied. These were only partially overcome by reversed-phase paper chromatography and although the classical adsorption chromatography worked very well for materials of this nature, no general analytical technique was available. The use by Izmailov and Shraiber (3) of a thin (2 mm) layer of powdered adsorbent, such as calcium oxide, magnesium oxide or alumina, to obtain *Laboratory of the Government Chemist, Ministry of Technology, London, S.E.1. 467