“…In acetonitrile and acetone, the system consisted of picric acid and tetra-n-butylammonium picrate and the pK AN a and pK AC a values used were 11.0 and 6.3, respectively [11,12]. In methanol, dimethyl sulfoxide and propylene carbonate the standardizing system comprised 2,6-dinitrophenol and tetra-n-butylammonium 2,6-dichlorophenolate with pK MeOH a , pK DMSO a , and pK PC a values of 7.8, 4.9 and 13.45 were applied, respectively [13][14][15]. The linearity of the E ¼ f ðlg c HA =c A À Þ plot in AN, AC, DMSO, and MeOH was obtained over the range À1 through 1 and in PC it was in the range from À0.5 to 1.…”