ACTIVITIES OF METHYL-ORANGE AND HOMOLOGS IN AQUEOUS-SOLUTIONS

The mean activity coefficients of Methyl Orange (MO), Ethyl Orange (EO), Propyl Orange (PO), and Butyl Orange (BO) in aqueous solutions ranging in concentration from 10** minus **3 to 10** minus **2mol kg** minus **1 have been determined by means of isopiestic measurements at 50 and 60 degree C respectively. It has been found that the mean activity coefficients of MO being the largest, and those of BO, the smallest. The coefficients have been found to decrease with an increase in the dye concentration. The examination of the results by Miliceivic treatment suggests that MO, EO, and PO are present as a monomer or a dinner, while BO exists as a trimer at 60 degree C.