Abstract
1 .0~ alcoholic solutions of 3-(4-methylphenylsulphonyl) 2,4 dimethyl 3H 1,5 benzodiazepine (I), 3 (4 hydroxy 3 carboxyphenylsulphonyl) 2,4 dimethyl-3H-1,5-benzodiazepine (II), 3-(4-hydroxy3 carbomethoxyphenylsulphonyl) -2,4dimethyl3H1,5-benzodiazepine (III) and 3-(4-hydroxy-3-carboethoxyphenylsulphonyl)-2,4-dimethyl3H 1,5-benzodiazepine (IV) were found to be very good indicators in acid-base titrations. The colour change is from pale yellow (in alkaline medium) to violet (in acid medium). It is very sharp and can be judged visually with great ease. 1 Part of indicator can be detected in 20000 parts of water. F rom detailed experiments it could be concluded that the indicators are useful if a weak base is titrated against a weak or strong acid. Most satisfactory results were obtained with indicator IV. Its colour change takes place within the pH-range from 6 . 9 5.2. With the other indicators this range is more or less the same.
Published Version
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