Laboratory Manual Of Elementary Colloid Chemistry

LABORATORY MANUAL ELEMENTARY -- PREFACE. -- ALTHOUGH most of the existing text-books of Colloid Chemistry necessarily give, in more or less detail, descrip- tions of experimental procedure and instructions for making many of the classical preparations, no laboratory manual or collection of practical exercises such as has been found indispensable in the teaching of other branches of chemistry has so far appeared. The lack of such a work is all the more likely to check the spread of a practical knowledge of the discipline, as many of the methods and materials of colloid chemistry are peculiar, and strange even to students well trained in inorganic and organic chemistry. The present work is an attempt to fill this gap and to supply accurate and very detailed directions for carrying out the fundamental operations, for making a number of representative preparations, and for examining them by the standard methods. These are based throughout on personal experience of the processes described and of the difficulties experienced in teaching them. The examples chosen are, generally speaking, the simplest ones and, where alterna- tives are possible, those involving the smallest expenditure in apparatus and material. The task of selection has not been easy, and the attempt to delimit the elementary region of the whole domain may seem premature or arbitrary the guiding principle has been to provide for the wants of those students of numerous branches of science who are finding some training in colloid chemistry an indispensable part of their equipment, and are able to devote a limited time only to acquiring its technique. For the guidance of readers desirous of going beyond the limits of this manuala number of references to recent literature are given at the end of each section. The papers quoted are mostly records of experimental investigations which are either alternative to, or more advanced than, the examples given in the text. Since the book is the first of its kind, the author will be very grateful for hints from readers who may find any of the directions given in it lacking in clearness or capable of being simplified. EMIL HATSCHEK. LONDON, February, I 920. CONTENTS. PAGE PREFACE . v CHAPTER I.-GENERAL REMARKS ON APPARATUS, MATERIALS AND PROCEDURE . 9 Choice of vessels, methods of cleaning the same. Making up solutions and sols. Filtration of sols. Distilled water. Redistilled water. Variability of materials and degree of accuracy. General hints. CHAPTER 11.-DIALYSIS . 16 Grahams dialyser. Parchment bags. Arrangements for continuous flow. Parchment tubes. Parchment thimbles. Collodion thimbles. Flat collodion membranes and Star dialyser. Dialysers for sols showing osmotic pressure. CHAPTER 111.-SUSPENSOID SOLS . 29 Gold sols reduction by tannin reduction by formaldehyde. Palladium sol. Silver sol reduction by dextrine reduction by tannin reduction by hydrogen. Various methods of making gold and silver sols. Sulphide sols cadmium sulphide sol arsenic sulphide sol. Miscellaneous sols Prussian blue sol ferric hydroxide sol. CHAPTER 1V.-SUSPENSIONS . 37 Mastic suspension. Other resins, dragons blood, gamboge. CHAPTER V.-ORGANOSOLS . 39 Reduction of silver in wool-fa. 0ther ietals in the same. CHAPTER V1.-EMULSOID SOLS AND GELS . 41 Silicic acid sol, preparation from water-glass. Salts promoting setting of sol. Determination of Si02. Effect of lyotropic salts. Gelatin.Commercial raw material. Swelling and dispersion. Filtration of sols. Hardness determination of melting and setting points. Examination of strained gels in polarized light. Agar. Swelling and dispersion. Filtration. Agar gel. Effect of lyotropic series on setting and swelling. Purified gelatin. Sols containing a definite amount per volume. CHAPTER VI1...