198 



NATURE 



[October 21, 19 15 



properties. Further subdivision is effected by 

 successive experiments on the reduction of the 

 dyes and the oxidisability of their reduction pro- 

 ducts. Owing- to recent intense activity in the 

 manufacture of synthetic dyes, each subdivison 

 nowadays contains apparently many members, 

 but, on the other hand, many of the names under 

 which dyes appear are only synonyms employed 

 by different firms. 



Although it is sometimes practically impossible 

 to identify the specific dyes on any fabric, yet 

 the author's scheme of analysis enables the 

 analyst to refer these substances to their appro- 

 priate classes, after which complete identification 

 may be achieved by comparative dye-tests with 

 standard dyes of known constitution. 



After a reference to the detection of artificial 

 dyestuffs in articles of food, the scheme for identi- 

 fying colouring matters on animal fibres is 

 elaborated. The dyed fabric is subjected to 

 "stripping- tests," and also to the action of a 

 reducing agent — in this instance, sodium form- 

 aldehyde - sulphoxylate (Rongalite). Separate 

 tests are described for indigoid dyes and for 

 mordants, and a few principles are laid down 

 for the examination of woollen fabrics dyed with 

 mixtures of dyes. In such cases, fractional re- 

 duction and " stripping " tests are useful, together 

 with fractional separation by means of solvents. 



The problem presented by dyed vegetable fibres 

 is much more complicated than that arising- from 

 dyed wool. Many basic dyes, which, when ap- 

 plied to wool, are readily .i^educed by sodium 

 hydrosulphite, are scarcely attacked by this 

 reagent when they are fixed on tannin-mordanted 

 cotton. Accordingly, the tannin mordant must 

 first be removed by boiling the fabric with caustic 

 soda solution saturated with sodium chloride, the 

 latter compound being added to avoid stripping 

 off the dye. 



Certain azo-co!ours, especially the insoluble 

 "ingrain" azo-derivatives formed on the fibre, 

 offer considerable resistance to the reducing- action 

 of ordinary hydrosulphite, and are decolorised 

 very slowly and imperfectly. To overcome this diffi- 

 culty the reducing agent is rendered more active 

 by the addition of a very small quantity of re- 

 ducible compound or colouring matter. The 

 most convenient catalyst or sensitiser for this 

 purpose is anthraquinone, a small quantity of 

 which is added to the sodium formaldehyde- 

 sulphoxylate solution. 



Indigo is still the premier blue dye, and on 

 account of its high price and valuable tinctorial 

 properties, the estimation of pure indigotin either 

 in bulk or on the fibre is a matter of considerable 

 commercial importance. Special attention may 

 be directed to the method for estimating quanti- 

 NO. 2399, VOL. 96] 



tatively the indigotin on animal fibres worked 

 out by the author in collaboration with Gardner, 

 Lloyd, and Frank, since this process affords an 

 accurate means of detecting the great abuses 

 obtaining in the prevalent practice of "topping" 

 or "bottoming" indigo-dyed materials with other 

 inferior colouring matters. 



The identification of organic colouring matters, 

 when carried out in the systematic manner advo- 

 cated by the author, becomes an important branch 

 of analytical chemistry, so that this handbook 

 may be recommended not only to the makers and 

 users of dyes, but also to all students of organic 

 chemistry. The educational value of the treatise 

 is well exemplified in the chapter on the deter- 

 mination of the constitution of azo-dyes, for the 

 methods adopted would go far towards enabling 

 the analyst to identify any one of the very large 

 number of azo-colouring matters at present on 

 the market. 



An index of the principal colouring matters 

 shows the position of these dyes in the analytical 

 separations, which are arranged in twenty-six 

 tables. 



The present condition of military warfare exist- 

 ing between the principal industrial nations will, in 

 all probability, be succeeded by a period of strenu- 

 ous industrial competition between the belli- 

 gerents. During this period the discoverers or 

 new dyes will, for obvious reasons, no longer, as 

 hitherto, endeavour to protect their discoveries by 

 patents, but will rely rather on keeping secret the 

 methods of manufacture and the chemical nature 

 j of the products. At this stage the analytical 

 methods systematised by the author will acquire 

 additional importance in their application to the 

 investigation of new dyes of undisclosed constitu- 

 tion. G. T. M. 



RUDIMENTARY SCIENCE FOR COAL- 

 MINERS. 

 An Introduction to Mining Science. A Theo- 

 retical and Practical Text-book for Mining 

 Students. By J. B. Coppock and G. A. Lodge. 

 Pp. x + 230. (London: Longmans, Green and 

 Co., 1915.) Price 25. net. 



THE object of this little book is to 

 put before the young coal-miner a 

 certain number of facts in elementary science, 

 mainly chemistry and physics, in such a way 

 as to impress them upon him more readily 

 than can be done through the medium of ordinary 

 text-books upon these sciences. Such subjects as 

 combustion, flame, explosion, the atmosphere, 

 mine gases, coal, etc., are treated, each in a 

 short chapter, which commences with a few ele- 



