Proceedings of the Society

It has been shown that the restraining effect of Dispersol VL upon leuco vat dyes is a function of the amountM present in the system and not of its concentration in the aqueous solution. A method of assessment of the relative sensitivities of individual leuco vat dyes has been evolved. By this method the relationship between the dyebath exhaustion and the amount of Dispersol VL in the dyebath, obtaining under given dyeing conditions, is experimentally determined. A sensitivity factor is then calculated from the slope of the initially linear graphical relation between these two variables. An anomalous behaviour has, however, been encountered with certain indanthrone derivatives. Evidence is presented to show the influence, on restraining effect, of varying the depth of shade, the temperature of dyeing, and the salt concentration of the dyebath. Investigations into the retarding and levelling effects of this non‐ionic body, as herein reported, indicate that these two properties are related to the restraining effect of Dispersol VL upon the leuco vat dye under consideration.