In taking up the industry for survey it has been thought desirable to first mention and describe the raw materials used; second, to outline the processes of manufacture; third, to classify the methods and illustrate by formulae the composition of various soaps together with their mode of manufacture; fourth, to enumerate the various methods of glycerine recovery, including the processes of saponification, and, fifth, to give the most important analytical methods which are of value to control the process of manufacture and to determine the purity and fitness of the raw material entering into it. It is not the intention of the author to go into great detail in this work, nor to outline to any great extent the theoretical side of the subject, but rather to make the work as brief as possible, keeping the practical side of the subject before him and not going into concise descriptions of machinery as is very usual in works on this subject. Illustrations are merely added to show typical kinds of machinery used. The author wishes to take this opportunity of thanking Messrs. L. S. Levy and E. W. Drew for the reading of proof, and Mr. C. W. Aiken of the Houchin-Aiken Co., for his aid in making the illustrations a success, as well as others who have contributed in the compiling of the formulae for various soaps. He trusts that this work may prove of value to those engaged in soap manufacture. E. G. T. January, 1922 TABLE OF CONTENTS. CHAPTER I. Page. RAW MATERIALS USED IN SOAP MAKING 1-30 1. Soap Defined 1 2. Oils and Fats 1-2 3. Saponification Defined 2-3 4. Fats and Oils Used in Soap Manufacture 3-4 Fullers' Earth Process for Bleaching Tallow 4-6 Method for Further Improvement of Color in Tallow 6 Vegetable Oils 6-9 Chrome Bleaching of Palm Oil 9-12 Air Bleaching of Palm Oil 12-16 5. Rancidity of Oils and Fats 16-18 Prevention of Rancidity 18 6. Chemical Constants of Oils and Fats 18-19 7. Oil Hardening or Hydrogenating 19-21 8. Grease 21-22 9. Rosin (Colophony, Yellow Rosin, Resina) 22-23 10. Rosin Saponification 23-24 11. Naphthenic Acids 24-25