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Oxazines as acid-base indicators. VIII. New indicators for titration in anhydrous acetic acid

Z. Stránský and V. Stužka

Department of Organic, Analytical and Physical Chemistry, Faculty of Natural Sciences, Palacký University, Olomouc


Abstract: In this paper, relative basicity constants of three oxazine indicator dyes towards the system antipyrine Perchlorate—antipyrine acetate in anhydrous acetic acid are determined. The constant К of 9-diethylamino-5H-benzo[a]phenoxazone-5, 9-dimethylamino-5H-benzo[a]phenoxazone-5 and 9H -benzo[a]phenoxazone-9 equals 1.53, 0.82 and 0.7 . 10-2, respectively.  A series of weak bases was titrated in anhydrous acetic acid using the above mentioned three indicators and it was shown by statistical analysis that the first indicator is convenient for titration of bases which рКa (H20) value is approximately 7—6, the second one for bases of pKa (H20) value about 5 and the third one for bases of pKa (H20) value between 3 and 2.

Full paper in Portable Document Format: 225a341.pdf (in Czech)


Chemical Papers 22 (5) 341–346 (1968)

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