CHARACTERIZATION OF THE IONIZATION AND SPECTRAL PROPERTIES OF SULFONEPHTHALEIN INDICATORS - CORRELATION WITH SUBSTITUENT EFFECTS AND STRUCTURAL FEATURES .2.

A spectrophotometric study is presented on the first ionization equili brium of a class of substituted sulfonephthaleins, whose second ioniza tion was the subject of the first part of this work. The present study was more difficult than the previous in that highly acid media and ac idity functions had to be used. Nevertheless the results were of suffi cient accuracy to allow the dual substituent analysis of Swain and Lup ton (C.G. Swain and A.C. Lupton, Jr., J. Am. Chem. Sec., 90 (1968) 432 8). Generally speaking, the dependences of equilibrium and spectral pa rameters on field and resonance parameters found in this and the previ ous paper were very similar.