V^ TURE 



271 



THURSDAY, DECEMBER 28, 1911. 



THE SYNTHETIC COLOURING MATTERS. 

 The Chemistry of the Coal-tar Dyes. By Prof. I. W. 

 Fav. Pp. vi + 467. (London : Constable and Co., 

 Ltd., 191 1.) Price 165. net. 



THE rate of progress in the dyestuff industry is 

 admittedly far more rapid than in any other 

 branch of applied chemistry, and the advances made 

 durincT the past ten or fifteen years have effected an 

 . normous change in the whole aspect of the subject. 

 Vorv many dyestuffs of former importance have been 

 ihaiidoiifd or partially replaced, and hundreds of new 

 Ivcsiuffs have been introduced into commerce. New 

 ■nanu'acturing- processes have superseded older ones, 

 md considerable improvements have been made in the 

 methods of dyeing and printing. The majority of 

 these advances have been directed towards securing 

 a greater degree of fastness to washing, light, and 

 other agencies. Thus in cotton dyeing the want of 

 fastness of the earlier " substantive " or " salt " dye- 

 stuffs soon led to attempts to fix these colours after 

 dyeing, by various methods, such as by diazotisation 

 and combination with phenols, by coupling with diazo- 

 compounds, by treatment with formaldehyde, or by 

 fixation with salts of copper or chromium. The intro- 

 duction in 1894 of Vidal black, and the enormous exten- 

 sion of the group of " sulphide " dyestuffs which shortly 

 followed, provided the cotton dyer with a class of 

 cheap colouring matters of much greater fastness than 

 ihose of the "salt" class, which they therefore 

 largely replaced. Again, more recently the newly in- 

 troduced "vat" dyes of the anthracene and indigoid 

 classes, though at present expensive and difficult to 

 apply, bid fair eventually to supplant the "sulphide" 

 dyestuffs for those purposes, in which the highest 

 degree of fastness is of paramount importance, since 

 many members of this class cxliiliit a resistance to 

 light and washing surpassing that of any of the older 

 organic dyestuffs. On the theoretical side also con- 

 siderable progress must be recorded. The constitution 

 of many dyestuffs and dyestuff groups has been 

 ehiridalcd, the mechanism o' reactions has been 

 niidi r( d clearer, and our views as to the connection 

 of chemical structure with colour and dyeing proper- 

 ties have been extended. 



In the presence of such rapid advances, existing 

 text-books soon become out of date, and in presenting 

 a n< \v work it should be the first aim of the author 

 to render an account of the subject from the most 

 modern point of view. This unfortunately Iia^ •,( .nci 1\ 

 hcf-n acromplished in the work under review. The 

 author has apparently drawn his material chiefly from 

 the standard W'xi-hooks, to which indiid he gives full 

 acknow Irdgmcnt. Orii^inal sourc-^, -.111 li as the scien- 

 tific and technical journals or the patent lil( raturc, do 

 not seem to have been consult(>d to any consid<rable 

 extent. In consequence many important dvi vtniK and 

 even entire groups of dyestuffs escape mention, wliilst 

 undue space is devoted to the description of others that 

 are now obsolete, and for which a short historical re- 

 ference would have sufiir.d. 1 Inis, among the azo- 

 NO. 2200, VOL. 88J 



dyestuffs we find no account of those derived from 

 pyrazolone, comprising the light-resisting dyes— tartra- 

 zine, fast light yellow, &c. ; nor of the more recent 

 chrome-azo colours obtained from orthoamidophenols 

 and orthoamidonaphthols ; nor of the valuable class 

 of substantive dyestuffs derived from the 2:5: 7-amido- 

 naphtholsulphonic acid. The very important group of 

 anthracene vat dyestuffs, of which indanthrene blue is 

 the typical representative, is also not mentioned ; 

 whilst thioindigo red and thioindigo scarlet are the 

 only vat dyestuffs of the indigoid class which are 

 described. 



Even amongst the older dyes .we note some curious 

 omissions. Thus no reference is made to the thiazol 

 class, which includes primuline, chloramine yellow, 

 and thioflavine, though this group still retains its 

 importance. Again, the stilbene condensation, by 

 which curcumine yellow and the mikado oranges are 

 produced, is only referred to in connection with the 

 preparation of diamidostilbene disulphonic acid, 

 whilst the reactions for the formation of this sub- 

 stance are represented in a manner now proved 

 by recent investigations to be erroneous. In describ- 

 ing the synthetical methods for the manufacture of 

 indigo, no reference is made to the technically im- 

 portant modification of Heumann's process employed 

 by the Farbwerke Hoechst, which consists in adding 

 sodium amide to the phenylglycine melt. Moreover, 

 the starting point in the Sandmeyer synthesis is not 

 chloral and hydroxylamine but diphenylurea. 



In regard to the more theoretical aspects of the sub- 

 ject, we miss any full discussion of the relationship 

 of constitution to colour, beyond the older views of 

 Witt. Paraquinonoid and orthoquinonoid formulae 

 are frequently used indiscriminately and without ex- 

 planation. Thus, whilst the paraquinonoid formula 

 is given to Lauth's violet, its tetramethyl derivative, 

 methylene blue, is represented on the same page by 

 an orthoquinonoid structure. Similarly, in the general 

 classification of the dyestuffs only paraquinonoid types 

 are given, whilst in the general text the dyes of the 

 azine, oxazine, and thiazine classes are mostly repre- 

 sented by orthoquinonoid formulae. The structure 

 assigned to quinoline yellow is the old quinophthalone 

 constitution now abandoned for the indanedione 

 formula. Chrysophenine is a diethylether of brilliant 

 yellow, and does not contain a free hydroxyl group 

 as formerly supposed and here represented. The fast- 

 ness to alkalis of the dyestuffs of the patent-blue class 

 cannot be due to the suggested intramolecular linkage 

 of the ortho-sulphonic group, since a similar effect is 

 produced by halogen atoms, or even by methyl groups 

 when present in the same position. 



Apart from the above defects, which perhaps arc 

 more serious from the point of view of the teihnologist 

 than for the general chemical student, the subject is 

 presented in an interesting and readable form, which 

 should render the volume of utilitv. The printing of 

 the text and formulae is unusually ilear, and for a 

 work of this kind fairly free from errors. 



The dedication of a whole chapter to the "seven 

 food colours" permitted by the I nii. d States Govern- 

 ment, appears somewhat a waste ut space even for 

 American readers. Arthuh G. Grekn. 



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