PrefaceAs in the preceding Handbooks of this series, the articles in COOLEY'S " Cyclopedia " have been added to from various scattered sources, so as to present, ill as small a compass as possible, information which, it is hoped, may be found useful to technological students and others interested in the industries described. In order to economize space, it has been assumed that the student has some previous knowledge of theoretical and practical chemistry, and details of many analytical processes, which are described in general treatises on practical chemistry, have been, for that reason, omitted. The Editor has pleasure in expressing his thanks to Mr. LEOPOLD FIELD, Lambeth, and to Messrs. COOK, East London Soap Works, for much valuable infor- mation, and to his colleague, Mr. CHAELES CAETEE, for assistance in revising the proofs.