May 9, 1907] 



NA TURE 



29 



understood that anything; like a complete treatment 

 of the diurnal variation requires a careful study of 

 the influence of the season of the year as well as the 

 relation to sun-spot frequency. The proposal advo- 

 cated by von Bezold and others to effect a line inte- 

 gration round a parallel of latitude ought before its 

 adoption to receive careful consideration from the 

 side of atmospheric electricity. It should be remem- 

 bered that the earth-air currents required to invali- 

 date the hypothesis embodied in the Gaussian 

 potential are not transient currents varying with the 

 hour of the day or with the weather — such currents 

 could only modify the magnetic diurnal inequality or. 

 cause irregular disturbances — but currents of prac- 

 tically constant value and direction over large areas. 



Since the above was written, science has had to 

 mourn the death of the distinguished author, Prof, 

 von Bezold, a fact already announced to the readers 

 of Nature (February 21, p. 397). 



Charles Chree. 



THE COLLOIDAL THEORY OF DYEING. 

 The Chemistry and Physics of Dyeing. By W. P. 



Dreaper. Pp. viii-(-3i5; illustrated. (London: 



J. and A. Churchill, 1906.) Price los. 6d. net. 

 "\T /"HEN it is remembered that dyeing has become 

 •^ ^ a highly scientific process, it is somewhat 

 strange to note what a small part theoretical con- 

 siderations have played in the practical development 

 of the art, a fact no doubt largely due to the lack 

 of definite knowledge of the chemical constitution of 

 te.xtile fibres. Most manuals of dyeing have been 

 written for practical ends, and have devoted small 

 space to the consideration of the various theories of 

 dyeing which have been put forward, since, as before 

 remarked, these have helped but little in the practical 

 solution of dye-house problems. Our knowledge of 

 the nature of fibres has, however, now reached a 

 point when it is undoubtedly of value that the scien- 

 tific dyer should make himself acquainted with this 

 side of his subject, and recent work on the nature 

 and properties of colloids certainly appears to throw 

 much new light on the intricate nature of dyeing 

 processes. 



It has, of course, long been known that one and the 

 same kind of fibre acts differently towards various 

 dyes, and that dyestuffs may be classified into groups 

 on the basis of this differentiation. To a considerable 

 extent this grouping is found to correspond with 

 fundamental similarities in the chemical constitution 

 of the dyes, and this broad fact has lent strong sup- 

 port to the chemical theory of dyeing. 



The older theories of dyeing could be broadly 

 classified into two groups, those assuming a chemical 

 reaction between fibre and dye, and those in which 

 dyeing phenomena are explained by the physical pro- 

 perties of the reacting bodies. To a great extent these 

 theories are antagonistic, and yet upholders of each 

 are able to put forward incontrovertible facts in their 

 support. It is, however, far from satisfactory to have 

 to assume that similar phenomena can be explained 

 NO. 1958, VOL. 76J 



in one case by a certain theory and in a second by an 

 opposite theory, and the time is ripe for a wider view 

 which shall embrace and reconcile all well-established 

 facts concerned with dyeing- processes. How far the 

 colloidal theory of dyeing is successful in doing this 

 may be gathered from a perusal of the book under 

 review. Much of the experimental work mentioned 

 lacks precision, and the various researches are some- 

 what detached, bilt the present knowledge of colloidal 

 conditions and functions, incomplete as it is, throws 

 much light on earlier work, and from further work 

 in this direction a satisfactory explanation of dyeing 

 processes may eventually emerge. In the past many 

 difficulties, in regard to dyeing theory as in other 

 directions, have arisen from an attempt to draw 

 a hard and fast line between chemical and physical 

 action, and the blending of the two may be considered 

 as the characteristic feature of the reactions of 

 colloids. 



The book is arranged in twelve chapters, of which 

 the first is devoted to a historical introduction, which 

 might with advantage have been considerably ex- 

 tended. The properties and reactions of fibres, 

 dyes, mordants, and assistants are dealt with in 

 chapters ii.-v. Chapter vi. contains an excellent sum- 

 mary of the recent work on the properties of colloids. 

 Chapter vii. gives facts in support of the old 

 mechanical theory of dyeing which reached its final 

 development in the solid solution theory of van 't Hoff 

 and Arrhcnius, which was applied to dyeing processes 

 by O. N. Witt. Chapters viii. and ix. give a similar 

 summary of facts supporting the chemical theory of 

 dyeing. Then follows in chapter x. an attempt to 

 show the application of the colloidal theory, and in 

 this the incompleteness of the evidence becomes 

 apparent, though as a suggestive contribution it is 

 very interesting. A chapter on the action of light 

 on dyeing operations and dyed fabrics appears to have 

 little connection with the central theme of the work. 



The many inaccuracies in the book lay it open to 

 a good deal of minor criticism. For example, on 

 p. 14 several of the formulae are altogether inexplic- 

 able. On p. 33 it is stated that Bancroft divided dyes 

 into subjective and adjective, the term used by Ban- 

 croft being substantive. A fair summary of the work 

 of various investigators is usually given in the text, 

 but it is often difficult to ascertain at what point the 

 summary ends and the author's comments begin. 

 There is thus some danger of injustice to one or 

 other. Since both centigrade and Fahrenheit thermo- 

 metric scales are used in the book, some confusion 

 arises in the frequent cases where a temperature 

 figure is given without indicating which scale it 

 refers to. Amongst mis-spelt authors' names may be 

 mentioned Verquin for Verguin, Pokorng for Pokorny 

 (several times), Prager for Perger, Brand for Brandt, 

 Boettinger for Bottiger, and Hirst for Hurst. 



The general plan of the book is excellent, and the 

 author's work, though somewhat unequal, is on the 

 whole very satisfactory. The production of such a 

 book would have been impossible a few years ago, 

 and it marks a distinct advance in the linking up of 

 one of the most ancient arts with modern scientific 



