June 22, 1893] 



NATURE 



17] 



i authors (Dr. Knecht) has himself made some very inte- 

 resting investigations in this field. But, in spite of all 

 that has been written, the subject of dyeing has still to 

 be taught as an art rather than as a science. The centres 

 'of the tinctorial industry in this country, such as Leeds, 

 Manchester, Bradford, and Huddersfield, are now pro- 

 jvided with Technical Schools, in which the dyeing 

 (department is made a special feature. If we might 

 .'venture to offer a word of advice to those who are pro- 

 viding for this industry, it is that adequate provision 

 itshould be made for the scientific side of the subject by 

 "the equipment of laboratories and the appointment of 

 jcompetent specialists for carrying on original investiga- 

 :!tion in connection with dyeing. The dyeing depart- 

 [iments in those schools which we have had the oppor- 

 j tunity of visiting are admirably equipped for instruction 

 rin the principles of the art, but the instructor has to 

 '{devote so much time to this part of the work, and the 

 'istudents who attend are, as a rule, so ill-prepared in 

 (general scientific training that the instruction given 

 Bcannot rise much above that handicraft level against 

 which the writer has had so frequently to protest in con- 

 nection with other branches of technology. Till this 

 jdefect is remedied, the results achieved by our technical 

 Schools will not be commensurate with the endowment 



restowed upon their equipment. 

 The work which has given rise to these reflections will 

 igo far towards placing the tinctorial art on a higher scien- 

 jUfic level. It is not, as the authors state in the preface, 

 ■fa mere 'cookery-book,' containing 'rule of thumb' 

 ■ recipes." A detailed analysis of its contents would be out 

 ^f place in these columns, but a general idea of its scope 

 nay be given. The introductory chapter, as already 

 stated, deals with the theory of dyeing. So far as wool 

 iiul silk fibres are concerned, the authors consider that 

 he evidence is in favour of a chemical as opposed to a 

 Kirely mechanical explanation : — 



'■ \ccording to the mechanical theory, wool dyed with 



enta, for instance, would simply absorb the unchanged 



Mochloride of the dyestuff, and thus assume the same 



olour in the solution of the dyestuff. But experiment 



lis shown that this is not the case. It absorbs the colour 



j.ise, which is, however, in itself colourless. Where then 



Iocs the colour come from ? We can come to no other 



oL^ical conclusion than that the colour base has combined 



lemically with some constituent of the fibre to form a 



ired salt." 



t this explanation does not enable us to see how the 

 "constituent" is combined with the other con- 

 1 lents of the fibre : — 



" This objection is easily met by assuming that what 

 's taken up is in chemical combination with some in- 

 i.joluble constituent of the fibre and is held by the rest of 

 lihe transparent or translucent substance of the fibre in a 

 [fctate of solid solution." 



|l Thus the theory advocated is partly chemical and 

 jliartly in that debateable region where chemistry and 

 j hysics have recently come into apparent collision. Re- 

 j earches in connection with the theory of dyeing have 

 Ciore than a purely technical value, and we hope that 

 il)r. Knecht will continue the good work which he has 

 ijommenced. With respect to cotton the authors state : — 

 !J " With the large numbers of direct cotton colours which 

 i|.re placed at our disposal, and which are continually in- 

 creasing in number, the question becomes more and more 

 || NO. 1234. VOL. 48] 



important from a theoretical point of view. It is not 

 probable that it will ever be solved by vague theoretical 

 speculations based on one or two known facts. In all 

 probability the solution of the question will require much 

 laborious work, including many quantitative determin- 

 ations." 



The technical part of the work begins with Part II., 

 dealing with the textile fibres of vegetable and animal 

 origin, such as cotton, flax, hemp, jute, China grass, wool, 

 silk, &c., not omitting Chardonnet's artificial "silk "pre- 

 pared from nitrated cellulose. The third part is devoted 

 to water from the dyer's point of view, and the fourth part 

 to washing and bleaching. Parts V. to VIII. deal with 

 the materials used in dyeing. All these materials are 

 classified into the three groups, Chemicals, Mordants, and 

 Dyestuffs, and are described under the collective (and 

 most objectionable) name of " drugs." The acids and 

 alkalies employed by the dyer are first treated of, then the 

 mordants, which are discussed in a very thorough 

 manner, no less than 150 pages being devoted to them. 

 Three parts (VI., VII., and VIII.) are devoted to the 

 natural, artificial organic, and mineral colours respectively. 

 The machinery used in dyeing forms the subject of 

 Part IX., the investigation into the tinctorial properties of 

 colouring matters that of Part X., and the concluding part 

 treats of the analysis and valuation of the materials used 

 by the dyer. There is an appendix of miscellaneous 

 subjects such as weights and measures, thermometer 

 scales, specific gravities, light and colour, &c. 



The foregoing synopsis of its contents shows that the 

 work is well calculated to fulfil the object which the 

 authors had in view, viz. to serve " as a book of reference 

 or vade mecum to the educated dyer." But it is not 

 really for an individual class that this book is written ; it 

 appeals to several distinct kinds of readers. It may 

 safely be asserted that there are few, if any dyers, in this 

 country, however " educated," who could with equal in- 

 telligence follow every section of the work under con- 

 sideration. The practical dyer who is most skilful in 

 applying colouring matters to fabrics is generally hazy in 

 his notions of chemistry, and absolutely ignorant so far as 

 concerns the finer questions of the "constitution " of the 

 complex products which chemistry has placed at his dis- 

 posal. In order to understand properly the chemical 

 portions of this manual a very sound foundation of 

 chemical science must have been previously laid. On the 

 other hand, a person who is thoroughly acquainted with 

 the chemistry of dyestuffs would be worse than useless — 

 he might be actually destructive — in the dye-house unless 

 he had been trained in the application of colouring matters 

 on a large scale. We are sometimes told that the practical 

 dyer need know nothing of chemistry ; that he would not 

 do his work any better when possessed of such knowledge. 

 There are still to be met with here and there so-called 

 " practical" men who go further and assert that the pos- 

 session of too much chemical knowledge would unfit the 

 dyer for his work. But public opinion appears to be under- 

 going a healthy change in this as in other departments of 

 technology. It may be long before we produce the ideal 

 technologist who is equally acquainted with the chemical 

 nature of his materials and the mechanical methods of 

 applying them. It appears, however, that this combin- 

 ation of knowledge is just what is wanted in the industry. 

 The joint authorship of the present manual perhaps 



