Water-soluble ferric amino-poly:carboxylate complex cpds. prodn. - providing purity required for photographic developers using cation exchanger

摘要

Prodn. of water-soluble Fe (III) aminopolycarboxylic acid complex cpds. (I) of the formula Y3FeIII n-1x3 (in which Y is an aminopolycarboxylic acid radical. n is its valency. X is an alkali metal or ammonium ion) involves (a) charging a cation exchanger with Fe (III) ions by passage of an aq. Fe (III) salt soln.; (b) passing an aq. soln. of an aminopolycarboxylic acid (II) of the formula YHn; and (c) elution of (I) using excess ammonium or alkali hydroxide (III). (I) are obtd. free from all impurities, as required for use in photographic developers, by a process suitable for mass prodn. In an example, a strongly acidic cation exchanger was charged quantitatively with Fe(III) ions using aq. FeCl3 soln., washed chloride-free, charged with EDTA and ammonia soln. and washed to give an eluate with a Fe/EDTA molar ratio of 1.2:1. The ratio was adjusted to 1:1 by adding solid EDTA and the pH was adjusted to 5.5 with ammonia.