THE CHEMICAL AGE- CHEMICAL DICTIONARY- CHEMICAL TERMS. Originally published in 1924. PREFACE: THE vast output of chemical literature at the present time is presenting almost insuperable difficulties to those who attempt to keep abreast of the rapid advances in chemical science. Not the least of these difficulties is the terminology of the subject, for chemical terms are multiplying at a bewildering rate. Frequently, too, when a new word or expression is coined it is followed up with an abbreviation or symbol by which it is expressed. One has, in fact, only to glance through the abstracts of the English and American Chemical Societies to realise the difficulty. The Chemical Age Dictionary of Chemical Terms has been compiled by experts to meet the needs of all those who have to consult not only original papers or their abstracts but other forms of lit erature as represented by reviews and modern textbooks. It will, therefore, make a direct appeal to all chemists from the student to the director of research. The subjects dealt with include organic, inorganic, physical, analytical and biochemistry. Unfortunately, many chemical terms are loose and even vague and it is very difficult, if not impossible, to give exact definitions in such cases. Indeed, it is undesirable to attempt to give an exact definition where none exists This is especially the case with names by which certain theories or concepts are known. In general the terms will be found in the form in which they are most frequently met with in technical literature, but in order to avoid repetition it has been found convenient in some cases to include a number of closely related terms under one general term. Thus, the different types of isomerism are classed together under Isomerism, the different kinds of spectra under Spectrum, and so on. Tide many laws, reactions, etc., are not grouped together under these headings but will be found under the names by which they arc known For example Henry's Law, and not Law of Henry, Hoesch Reaction, and not Reaction, Hoesch van't Hoff factor and not Factor, van't Hoff. In many cases cross-references are given not only to the same subject but to cognate subjects. No effort has been spared to illustrate the explanations and definitions by means of examples; and it is hoped that these will be of great assistance in elucidating terms which could not otherwise be made perfectly clear. The Dictionary is an essential supplement to, but not a substitute for, the textbook. The present dictionary is intended to be the forerunner of successive volumes, each one of which will deal with the subject as it appears in its different phases. Thus, it is hoped to publish a second volume dealing with Organic Substances, a third dealing with Inorganic Substances, etc. No Dictionary compiled on similar lines has as yet appeared in the English language. It is hoped, therefore, that the present volume will prove not only a novelty, but an indispensable companion for all those who are interested in pure chemistry or its application to industry. LONDON / September, 1924 CONTENTS PAGE PREFACE .....------5 A..... 9 B....... 24 C...... 30 D.......45 E.......56 F.......64 G.....69 H.....74 I J K....92 L.....94 M....97 N.....106 O P....117 Q...128 R...130 S....135 T.... 145 U....151 V...... I81 W J 54 X 155 2 J 56 TABLE OF SYMBOLS ----------* 57 THE CHEMICAL AGE CHEMICAL DICTIONARY: CHEMICAL TERMS Absolute Zero. The temperature 273 centigrade. Temperatures measured from this zero are termed absolute temperatures and are generally designated by a capital T If t is the temperature centigrade then T = 273 - ft . Absorptiometer. An apparatus for deter mining the solubility of gases in liquids. It consists of a graduated vessel containing the liquid and a known volume of gas; or the absorption may be done in a separate vessel, the gas being measured out from a burette There are several modifications of thes