488 Dr. BoUey on the Theory of Dyeing. 



1. Wool, silk, and cotton are coloured by the penetration of 

 the dye. Under the microscope they appear evenly impregnated 

 with colour, and transparent. Stuffs dyed with chromate of lead 

 and oxide of chromium form an exception, being coloured partly 

 by adhesion of the dye to the surface, partly by its penetration 

 throughout the substance of the fibre. In some exceptional cases 

 the colour of black silk is due to a crust which adheres only 

 slightly to the outside of the fibre. This crust easily breaks off 

 and shows the fibre coloured uniformly by penetration. With 

 these exceptions, fibres are universally coloured by penetration 

 of the dye, and its intimate union with the substance of the 

 coloured material. 



3. The processes actually employed for dyeing different sub- 

 stances differ according to the nature of the fabric. While, for 

 instance, fibres of animal origin, such as wool and silk, take up 

 colouring matter from a solution containing a metallic salt as 

 mordant, woody fibres under the same circumstances do not 

 receive the slightest trace of colour. In order that cotton, flax, 

 or hemp may take a dye that neither washing with water nor 

 friction shall be able to remove, the colouring matter must be 

 rendered insoluble after it has penetrated the substance of the 

 fibre. JFool and silk, on the other hand, seem to possess a genuine 

 affinity for colouring matter mixed loith a mordant. 



3. He found that wool and silk, treated with solutions of alu- 

 mina, iron, and tin salts, possessed the property of fixing a certain 

 portion of the base of the mordant. 



The following is a tabular view of these results : — 



Wool treated with alum, contained in 100 parts 0"75 ash. 



„ the same „ „ 0"72 „ 



J, sulphate of alumina „ 0"86 „ 



„ alum and cream of tartar I*] 2 „ 



„ acetate of iron „ „ 0'75 „ 



„ perchloride of tin „ 1"25 „ 



Silk treated with acetate of alumina „ 1-50 „ 



„ acetate of iron „ „ TOO „ 



„ alum. „ „ 0-40 „ 



Finally, 0. Maschke* published a treatise, the object of which 

 was not, indeed, to propound a theory of dyeing, but in which 

 observations are recorded that bear so immediately on the fore- 

 going questions that we cannot venture to pass them over. The 

 treatise in question is entitled " Pigmentlosung als Reagens bei 

 niikroskopisch-physiologischen Untersuchungeu." 



In the first place, the most important results of Hartig's 

 researches on ihe effect of certain pigments on the cell-contents 



* JmirnalfurPrakt. Chemie, v. Erdmann und Werther, vol. Isxvi. p. 37. 



