COMMON COMMODITIES AND INDUSTRIES SERIES Each book in crown 8vo, cloth, with many illustrations, charts, etc., 2/6 net TEA. By A. Ibbetson COFFEE. By B. B. Keable SUGAR. By Geo. Martineau, C.B. OILS. By C. Ainsworth Mitchell, B.A., F.I.C. WHEAT. By Andrew Millar RUBBER. By C. Beadle and H. P. Stevens, M.A., Ph.D., F.I.C. IRON AND STEEL. By C. Hood COPPER. By H. K. Picard COAL. By Francis H. Wilson, M.Inst., M.E. TIMBER. By W. Bullock COTTON. By R. J. Peake SILK. By Luther Hooper WOOL. By J. A. Hunter LINEN. By Alfred S. Moore TOBACCO. By A. E. Tanner LEATHER. By K. J. Adcock KNITTED FABRICS. By J. Chamberlain and J. H. Quilter CLAYS. By Alfred B. Searle PAPER. By Harry A. Maddox SOAP. By William A. Simmons, B.Sc. (Lond.), F.C.S. THE MOTOR INDUSTRY. By Horace Wyatt, B.A. GLASS AND GLASS MAKING. By Percival Marson GUMS AND RESINS. By E. J. Parry, B.Sc., F.I.C., F.C.S. THE BOOT AND SHOE INDUSTRY. By J. S. Harding GAS AND GAS MAKING. By W. H. Y. Webber FURNITURE. By H. E. Binstead COAL TAR. By A. R. Warnes PETROLEUM. By A. Lidgett SALT. By A. F. Calvert ZINC. By T. E. Lones, M.A., LL.D., B.Sc. PHOTOGRAPHY. By Wm. Gamble ASBESTOS. By A. Leonard Summers SILVER. By Benjamin White CARPETS. By Reginald S. Brinton PAINTS AND VARNISHES. By A. S. Jennings CORDAGE AND CORDAGE HEMP AND FIBRES. By T. Woodhouse and P. Kilgour ACIDS AND ALKALIS. By G. H. J. Adlam _OTHERS IN PREPARATION_ [Illustration: _Copyright by Messrs Flatters & Garnett, Manchester_ BACTERIA NODULES ON THE ROOT OF LUPIN] PITMAN’S COMMON COMMODITIES AND INDUSTRIES ACIDS, ALKALIS AND SALTS BY G. H. J. ADLAM, M.A., B.Sc., F.C.S. Editor of “The School Science Review” London Sir Isaac Pitman & Sons, Ltd., 1 Amen Corner, E.C.4 Bath, Melbourne and New York Printed by Sir Isaac Pitman & Sons, Ltd., London, Bath, Melbourne and New York PREFACE It has often been said, and still more often implied, that considerations of utility in education are incompatible with its main object, which is the training of the mind. Extremely divergent views have been expressed on this point. Schoolmen have looked askance at some branches of knowledge because they were supposed to be tainted with the possibility of usefulness in after life. On the other hand, business men and others have complained bitterly of the present state of education because very little that is considered “useful” has up to the present been taught in schools.