SPECTROPHOTOMETRIC STUDY OF THE EFFECT OF SODIUM DODECYL-SULFATE ON THE ACID-BASE BEHAVIOR OF 4-(2-PYRIDYLAZO)-RESORCINOL

The values of the apparent dissociation constants of the azo dye 4-(2-pyridylazo)-resorcinol (PAR) have been found in the presence of sub- and supercritical concentrations of the anionogenic tenside sodium dodecyl sulphate (SDS) and the effects of the strong electrolytes NaCl and NaNO3 were also evaluated. In both electrolytes, the pK(an) values initially are independent of the SDS concentration and then increase. Spectrophotometric and surface tension measurements were employed to determine the critical micelle concentration (cmc) of SDS alone and in the presence of PAR and the given electrolytes. The determined cmc values were in the range 0.20-3.02 mmol. .1(-1) and depended on the type and concentration of the particular additive.