STUDIES ON METHYLTHYMOL BLUE .I. SEPARATION AND PURIFICATION OF METHYLTHYMOL BLUE AND SEMIMETHYLTHYMOL BLUE

The metallochromic indicator Methylthymol Blue was purified chromatographically with cellulose and ion-exchange resin columns. The monosubstituted product of the reaction, Semimethylthymol Blue, was also separated and purified, and can also be used for the colorimetric determination of metals. There are not marked differences between the infrared spectra of Methylthymol Blue and Semimethylthymol Blue. The purities of Methylthymol Blue and Semimethylthymol Blue finally obtained were above 97% and 90% respectively. In acidic medium Methylthymol Blue forms 1:1 greyish blue and 1:2 pure blue chelates with copper(II) whilst Semimethylthymol Blue forms only 1:1 orange chelates with bivalent metals. The molar absorptivities at 435 mμ are 1.89 (± 0.03) × 104 for Methylthymol Blue at pH 5.00 and 1.76 (± 0.03) × 104 for Semimethylthymol Blue at pH 5.45. © 1969.