酸塩基指示薬の分光光度的研究

概要

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Although some acid-base indicators have been investigated from a spectrophotometrical viewpoint, the systematic study of most indicators has been lacking. In the present paper the spectra of about 30 kinds of indicators commonly used were measured at various pH values. As a result, indicators were divided into three types with regard to the variation of hue.<BR>Type A: Both the maximum and minimum appear in the absorption curve, and their positions are interchanged with each other at the extreme pH values of transformation interval (See Fig. 2).<BR>Type B: The position of the absorption maximum changes as pH is varied (See Fig. 19).<BR>Type C: The position of the absorption maximum does not change, but the absorbancy changes as pH is varied (See Fig. 28).<BR>From an inspection of chemical structure, it was found that sulfonephthalein dye belongs to Type A, azo dye to Type B, and phthalein dye to Type C. And, in addition, theoretical consideration was given to the isosbestic point and to the position of the absorption maximum in absorption curves.
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