622 REPORT— 1903. 



Le triplet 7 (3807 a 3791) parait s'effacer pour une ' self plus faible encore. 



La partie plus r^franpjible du spectre ne pr6sente plus d'iiit<5ret astronomique, 

 car elle est arret6e par Fabsorption atmospherique. Je I'ai etudi^e avec un spectro- 

 ^raphe a partie optique toute en quartz ; la raie 2642 disparait pour les memes 

 valeurs de ' self-induction ' que ci-dessus, c'est-a-dire pour moins de 0'^0062. Toutes 

 les autres lignes, notamment le groupe caracteristique de six raies (2529 a 2507) 

 fit le groupe (2217 ii 2208), resistent absolument a la ' self-induction ' maximum. 

 J'ai enfiu reconnu que la ligne extreme 1930-0 n'appartient pas au silicium mais 

 bien a I'aluminium. 



Ces recberches ont 6t6 faites avec du silicium cristallis^ en petits octaedres et 

 en lamelles, puis avec le silicate de sodium fondu au cbalumeau, sur des fils de 

 platine. Comme je I'avais deja signale ^ Taction de la 'self-induction ' est la meme 

 sur les corps solides ou les sels fondus. 



Les longueurs d'onde ont ete mesur^es par comparaison avec celles des raies 

 dim alliage plomb-cadmium, photographiees sur cbacun des spectrogrammes. 



IL The Theory of Dyeing. 5y Professor G. von Georgievics. 



Tbe author gives a brief historical mtroduction to the subject of tinctorial 

 chemistry, and observes that the study of this branch of applied science has been 

 greatly complicated by the publication of large masses of incompletely observed 

 facts. He further remarks that practical unanimity prevails as to the nature of 

 the dyeing process in so far as concerns the application of colours such as chrome 

 yellow, nitraniline red, and the mordant colours ; these colours, or compounds of 

 the colours -with the mordant, are deposited as such upon the fibre. 



The theories, or, more properly, the hypotheses, concerning the nature of dyeing 

 refer more particularly to the so-called substantive colours — that is, to dyeing with 

 acid colours, basic colours, and direct colours. The principal theories of the pro- 

 cess of dyeing are two in number — namely (1) the chemical theory, and (2) the 

 mechanical theory. In accordance with the first, the dyeing of wool and silk with 

 basic and acid colours is due to the formation of chemical compounds between the 

 colour and the fibre ; the chemical combination is supposed to be of a loose, salt-like 

 nature, because the combined colour exhibits a chemical behaviour identical with 

 that of the free colour. 



The chemical theory offers no plausible explanation of dyeing with direct cotton 

 colours (salt colour."?). 



The mechanical tlieory describes the process of dyeing as one of absorption or 

 of solution. Some writers attempt to compromise by describing the dyeing pro- 

 cess as partly chemical and partly mechanical in nature, whilst others are of the 

 opinion that the dyeing changes in character with the dye-stuff and the fibre. 



In discussing what is required of a theory of dyeing," the author states the view 

 that such a theory can be nothing more nor less than an expression of all the 

 hitherto known facts concerning tbe process. The supporters of tbe mechanical 

 theory of dyeing do not deny the possibility of the existence of chemical combina- 

 tion, more especially as all colours are of acid or basic nature, and the animal 

 textile fibres, at least, are not chemically indifferent; they claim, however, that the 

 existence of such a chemical combination has not been hitherto proved in any single 

 case, whilst all the observed facts tell in favour of the chemical theory. The sup- 

 porters of the chemical theory of dyeing put forward as specially important pieces 

 of experimental evidence two statements, both made by E. Kuecht, the one refer- 

 ring to the dyeing of basic colours on wool and silk, the other to dyeing with acid 

 colours. In accordance with the first statement, wool and .silk play the part of 

 acids towards basic colours, and the corresponding coloured compounds must be 

 regarded as salts of the colour with keratin or fibroin respectively, because in such 

 dyeing processes the acid is quantitatively split ofl' from the colouring matter and 

 only the colour base is taken up by the fibre. It is further suggested that the 



> Comptes Hendvs de VAcad. d. Sciences d. Paris, 5 et 26 mai 1902. 



