DIRECT DYEING OF CELLULOSE

The fading rate of Zambesi Black D (I) (C. I. Drect Black 17 C. I. 27700) and Aniline→p-cresidine→r-acid (II) for cellophane films was measured and CF curves of these dyes were determined by the Giless method. (I) contains two groups at the ends of conjugated chain which probably favours the bond formation. (II) contains only one group at one end.The following observations are reported: There is no linear relationship between the logarithm optical density and irradiated time of these dyes on cellophane films i. e. the rate should not decrease exponentially with time. But when the 1/optical density is used for the vertical axis, the curve makes a straight line. These dyes are faded according to the second-order law in appearence. The fading reaction of (I) and (II) must therefore occurs in the same form.Giles found that the intercepts of the CF curves on the y-axis for azoic dye rise with increase in the average particle size as judged visually under a microscope (Baxter, Giles. Miss Mc Kee and Macaulay, J. Soc. Dyer Col., 71, 218 (1955)). These dyes in cellophane films have a positive slope. The intercepts of the CF curves on the y-axis for (II) rise more than (I). It may be supposed that (II) is in some form of more increased aggregated state than (I).