T. Katayama, H. Miyata, K. Tǒei
Nov 1, 1971
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0
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Journal
Bulletin of the Chemical Society of Japan
Abstract
In order to clarify the effect of the hydroxyl group at the 5-position of chromotropic acid on the chelate stabilization, the following six reagents were synthesized by the coupling with 4-hydroxynaphthalene-2,7-disulfonic acid or 4,5-dihydroxynaphthalene-2,7-disulfonic acid(chromotropic acid): 2-(m-sulfophenylazo)-1-hydroxynaphthalene-3,6-disulfonic acid(I), 2-(o-methoxy-m-sulfophenylazo)-1-hydroxynaphthalene-3,6-disulfonic acid(II), 2-(o-hydroxy-m-sulfophenylazo)-1-hydroxynaphthalene-3,6-disulfonic acid(III), 2-(m-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid(IV), 2-(o-methoxy-m-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid(V), and 2-(o-hydroxy-m-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid(VI). The acid dissociation constants of these reagents and the stability constants of their metal chelates with magnesium and calcium were measured by the pH titration method at an ionic strength of 0.10 and at 25°C. From the results obtained, it has become apparent that ...