Effect of Crystal Modification on Dyeing Behaviour of Disperse Dyes

Meetings of the Manchester Region held at the Manchester Literary and Philosophical Society, Manchester, on 15 January 1970, Mr H. R. Hadfield in the chair; and of the Leeds Junior Section, held in the Department of Colour Chemistry and Dyeing, University of Leeds, on 19 January 1970, Mr K R. F. Cockett in the chair The dye 2‐nitroaniline‐4‐ethylsulphone, 1‐phenyl‐3‐methyl‐5‐aminopyrazole (aminopyrazole yellow) has been isolated in five different crystal modifications. The saturation values of these modifications in cellulose acetate have been determined at 80°C. Crystal modifications are important in the disperse dyeing of cellulose acetate and polyester materials because of their influence on colour yield and the stability of the dispersion.