666 SCIENCE PROGRESS 



( i) Synthetic Colouring Matters. Dyestuffs derived £rom Pyridine, Quinoline, 

 Acridine, and Xanthene. (Monographs on Industrial Chemistry.) By 

 J. T. Hewitt, M.A., D.Sc, F.R.S., Emeritus Professor in the East 

 London College. [Pp. xi + 405.] (London: Longmans, Green & Co., 

 1922. Price 14s. net.) 



(2) iThe Manufacture of Dyes. By (the late) John Cannel Cain, D.Sc. 

 [Pp. ix + 274.] (London : Macmillan & Co., 1922. Price 12s. 6d. net.) 



(i) It is a healthy sign that the British dye industry is slowly but surely pro- 

 ducing a literature of its own, and Sir Edward Thorpe is to be congratulated 

 on having arranged for the production of some half-dozen monographs cover- 

 ing the various groups of dyes, the present volume by Prof. Hewitt being 

 the first of this section of the " Monographs on Industrial Chemistry." 



Hitherto there has been no class of works between the various general 

 textbooks on dyes, which necessarily cannot deal in great detail with the 

 different groups of dyes, and such massive productions as Winther and Fried- 

 lander, which cover chiefly the patent literature. 



For this reason Prof. Hewitt's summary of our present-day knowledge of 

 the dyes of the pyridine, quinoline, acridine, and xanthene dyes is very wel- 

 come, and will be read with great interest by all those who work with these 

 classes of colouring matters. 



The growth of the subject is indicated by the fact that it was originally 

 intended to include the acridines, xanthenes, azines, and oxazines in one 

 volume, but it was soon found to be necessary to write two books, the oxazines 

 and azines in one and the xanthenes and acridines in the other, and to include 

 in the latter a chapter on the important work which has been done lately, 

 chiefly at Cambridge, on the sensitising dyes of the quinoline series, and thus 

 providing an excellent summary of the present state of our knowledge of 

 this group. 



The chief objection that may be lodged against the work is that the extracts 

 from patents are too long and detailed ; the general results claimed in any 

 given patent where several examples are quoted could best be given in tabular 

 form, whilst the actual quantities given could well be omitted ; as the author 

 truly says, " a specification does not always contain the whole truth and 

 nothing but the truth." 



There are a certain number of misprints such as " Ehtmyl " for " Methyl " 

 on p. 201, " quionline " for " quinoline " on p. 54, whilst the formula for 

 butanol on p. 54 is incorrect. 



These, however, are minor points, and may well be disregarded in passing 

 judgment upon this valuable contribution to chemical literature. 



(2) It is somewhat difficult to criticise a posthumous work by one who 

 was so recently amongst us, without knowing just what was intended, and as 

 Prof. J. F. Thorpe points out in his preface, it has been printed practically 

 as it was left, so that many matters which might otherwise have been revised 

 by the author have remained as they were. 



It is fairly obvious that Dr. Cain intended the book to be a supplement to 

 his earlier volume. The Manufacture of Intermediate Products for Dyes, and the 

 general style of the book is similar to that volume. 



The work is, of course, largely a rechauffe of recipes and patents from 

 elsewhere, though it is none the less useful on that account, as an examination 

 of its pages will often save a good deal of work in looking up references. 



It is evident, however, that the book in its present incomplete form is 

 only an outline of the finished work which Dr. Cain no doubt had in mind, 

 and there is a certain air of sketchiness and lack of detail in many parts which 

 shows that it was intended to expand these pages before publication. Many 

 of the paragraphs on azo dyes, for instance, are so short and lacking in all 

 detail as to be valueless. The two pages devoted to indigoid and thioindigoid 

 dyes are quite inadequate for dealing with this most important class of dyes. 



