2 HUBNER, Characterisation of Mercerised Cotton. 



mercerised cotton is of a brownish-black shade whilst the 

 ordinary cotton appears practically white. If now water 

 is added the colour of the mercerised cotton changes 

 immediately into a blueish-black the ordinary cotton 

 remaining white. 



It is well known that cotton treated with caustic soda 

 solution exhibits increased affinity for the substantive 

 cotton colours and that a considerable contraction takes 

 place during this treatment. Hiibner and Pope (Joe cit.) 

 have shown that both the maximum absorption of colour, 

 and the highest shrinkage of the fibres result from mer- 

 cerising the cotton with caustic soda solution of from 50 

 to 60° Tw. They have also pointed out that the ratio of 

 colour absorption and of shrinkage is not directly com- 

 parable with the increase of the strength of the caustic 

 soda solution. 



On applying the reagent described above to cotton 

 mercerised with caustic soda of different strengths, it has 

 been found that a distinct gradation of colour, directly 

 comparable with Hiibner and Pope's results, is produced. 



On exposing the blue-coloured cotton, after washing, 

 to the air, it will be noticed that on drying the colour 

 fades gradually, and the more slowly the stronger the 

 caustic soda which has been used in the mercerising of 

 the material. If the cotton, after immersion in the 

 reagent, is either not washed at all, or washed with 

 potassium iodide solution, the brown colour of the 

 ordinary and of the weakly mercerised cottons is seen to 

 fade rapidly and very completely on drying, whilst the 

 more strongly mercerised cottons retain the iodine for a 

 very long time. Some of the samples have not faded 

 after an exposure of six weeks. 



The action of salts other than potassium iodide is at 

 present under observation. 



