374 BEPORT— 1893. 



until all have been examined. There is no doabt but that the behaviour 

 of dyed colours towards light and other agencies depends upon several 

 factors, 6.17., the chemical constitution of the colouring matter itself, the 

 kind of fibre to which it is applied, the method of application, &c. With 

 so many variables a full and complete examination of the question of the 

 fastness of dyes proves to be one of extreme complexity and difficulty. 

 Even to determine effectually the nature of the relationship existing be- 

 tween the molecular constitution of colouring matters and their behaviour 

 towards light seems to necessitate the employment of chemically pure 

 dye-stuffs, and that the dyeing should be so arranged as to have an equal 

 number of molecules of colouring matter on a given weight of textile 

 material. Having regard, therefore, to the difficulties connected with the 

 purification of such a large number of colouring matters as are now in 

 use, their varying colouring power, the different degree to which they 

 exhaust the dye-bath, &c., it seemed better, for the present at least, to 

 confine our attention to a comparison of the relative fastness to light of 

 the various distinct commercial colours, the results of which might form 

 a basis for a further examination in the direction alluded to. 



The dyed and faded patterns have been entered in pattern-card books 

 in such a manner that they can be readily compared with each other. 



The following tables give the general result of the exposure experi- 

 ments made during the year 1892-93, the colours being divided, according 

 to their behaviour towards light, into the following five classes : Very 

 fugitive, fugitive, moderately fast, fast, very fast. 



The initial numbers refer to the order of the patterns in the pattern 

 books. The S. and J. numbers refer to Schultz and Julius' ' Tabellarische 

 Uebersicht der kiinstlichen organischen Fai-bstoffen.' 



Class I. Very Fugitive Colours. (Wool.) 



The colours of this class have faded so rapidly that at the end of 

 the first ' fading period ' (May 24 to June 14, 1892) only a very faint 

 colour remains, and at the end of the fifth period (one year) all traces 

 of the original colour have disappeared, the woollen cloth being quite 

 white or of a yellowish tint. 



Triplienyhnethan Colours. Phthaleins. 

 Wool Book II. 



Eosins. 1. Eosin A. Alkali salt of tetra-brom-fluorescein. S. and J. 319. 

 „ 2. Erythrosin G. Alkali salt of di-iodo-fluorescein. S. and J. 324. 



„ 3. Methyl-eosin. Potassium salt of tetra-brom-fluorescein-methyl-ether. 



S. and J. 320. 

 „ 4. Erythrosin JN pure. Sodium salt of tetra-iodo-fluorescein. 



„ 5. Eosin S. Potassium salt of tetra-brom-fluoresce'in-ethyl-ether. S. and 



J. 321. 

 „ 6. Eosin F. Same as i. 



„ 7. Phloxin P. Potassium salt of tetra-brom-di-chlor-fluoresce'in. S. and 



J. 325. 

 . „ 8. Eosin BN. Potassium salt of di-brom-di-nitro-fluorescein. S. and 



J. 322. 

 „ 9. Erythrosin B. Sodium salt of tetra-brom-tetra-chlor-fluorescem. 



S. and J. 328. 

 „ 10. Cyanosin (spirit soluble). Potassium salt of tetra-brom-di-chlor-fluores- 



cein-methyl-ether. S. and J. 326. 

 „ 11. Cyanosin B. Sodium salt of tetra-brom-tetra-chlor-fluorescein-ethyl- 



ether. S. and J. 329. 

 „ 12. Phloxin tetra (pure). Same as 9. 



