118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. 948 REVIEWS OF BOOKS BOOKS RECEIVED. Fifth Report on Colloid Chemistry and its Oeneral and Industrial Ap= plications. (London, I923 : H.M. Stationery Office. Pp. 130. Price 2s. 6d.) This is the fifth Keport of the Committee of the British Association on colloid chemistry, of which Professor F.G. Donnan is Chairman and Dr. W, Clayton, Secre- tary. In addition to the following papers the Report contains an Index to the whole series of five Reports, as it is not proposed to issue any more. Contents.-The Measurement of Surface Tensions. By Allan Ferguson. Report on Collagen and Gelatin. By Professor H. R, Proctor, D.Sc., and John Arthur Wilson. Industrial Applications of Wetting Power. By W. H. Nuttall. Colloids in Relation to the Manufacture of Inks. The Manufacture of Artificial Silk in Relation to Colloid Chemistry. By Edward Wheeler. Refractories for Electric Furnaces. Published by the American Electro- chemical Society, Columbia University, New York City. (Pp. 94. Price to members of the Faraday Society, one dollar.) This Report is based on the proceedings of one of the meetings of the Electric Furnace Association of America, but fresh material has been added, CoittEnts.-Refractories for Electric Furnaces.By Raymond M. Howe. Refrac- tories for Electric Furnaces. By Clyde E. Williams. Some Properties of Refrac- tories. By R. T. Stull. Refractories for Electric Furnaces. By Homer F. Staley. Electric Furnace Refractories. By C. W. Berry. Aluminous Refractories for Electric Furnaces. By L. C . Hewitt. Electric Furnace Refractories. By A. F. Greaves- Walker. Carborundum Refractories in Electric Furnaces. By M. L. Hardmann. Re- fractories for Electric Furnaces. By Refractories Dept., Norton Co., Worcester, Mass. Discussion. Index. Chemical Synonyms and Trade Names.By WILLIAM GARDNER (London, This Dictionary which, we believe, is the only book of its kind, gives the chemical names corresponding to the synonyms and trade names (and vice versa) of chemical materials commonly employed in manufacture and pharmacy. The book contains 14,000 definitions and cross references and the entries include minerals, dyestuffs, ex- plosives, pigments, drugs, alloys as well as the chemicals in common use. Discours de la Nature de Pair.-de la Vkgktation des P1antes.-Nouvelle Dicouverte touchant la Vie: By EDME MARIOTTE. (Paris, 1923 : Gauthier-Villars et Cie. Pp. I 18. This is another volume in the Series “ Les Maitres de la PensCe Scientifique.” Physicists will greatly welcome a reprint of Mariotte’s famous essay on the Nature of Air in this cheap and haqdy form.By C. A. Mitchell. 1924 : Crosby, Lockwood & Son. Pp. 271. Price 2 5 s . )BOOKS RECEIVED 949 The Thermal Properties of Ethyl Chloride. A special report by the Engineering Committee of the Food Investigation Board. (Published by the Dept. of Scientific and Industrial Research. Pp. 35. Price 13s. 6d. To be obtained from H.M. Stationery Office.) Studies from the Plant Physiological Laboratory of Charles University, Prague. Vol. I. Edited by Professor Dr. B. N~MEC. (Published by the University, Prague. The Formation of Transverse Fissures in Steel Rails and their Prevalence on Certain Railroads-Report of the Interstate Commerce Commission. (Published by the Bureau of Safety, Washington. Third and Final Report. (Published by the Department of Scientific and Industrial Research. Pp. 30. Porosity. Contributions from the Department of Ceramic Engineering, Univer- sity of Illinois. (Reprinted from the Journal of the Americari Ceramic Society.) Abstract Bulletin of the Nela Research Laboratory. National Lamp Works of General Electric Company, Cleveland, Ohio. Vol. I., No. 3. October, 1922. Vol. XI. A record of investigations undertaken by members of the Manchester College of Pp. I I 9.) Pp. 169.) Mine Rescue Apparatus Research Committee. Price IS. net. To be obtained from H.M. Stationery Ofice.) The Journal of the Municipal College of Technology, Manchester. Technology.ABERDEEN : THE UNIVERSITY PRESS