POTENTIOMETRIC DETERMINATION OF THE IRON CONTENT OF THE SAPONIFICATION BATH.

The authors describe a procedure for the potentiometric complexometric determination of iron in a saponification bath, in the concentration range of 1-20 mg/dm**3. The procedure includes the following steps: (1) Conversion of all the iron compounds into the ionic state, to do which the sample top be analyzed is acidified to pH 1. 8-1. 9, controlling the pH with a glass electrode. This pH value is optimum for further operations. (2) Conversion of Fe**2** plus to Fe**3** plus , for which an oxidant is added to the sample for analysis, to oxidize sulfite ion and Fe**2** plus . For this purpose one can use only those oxidants which do not form a redox system after reduction that interferes with the complexometric titration of Fe**3** plus , which is based on a change in the redox potential of the Fe**3**30 /Fe**2**30 system.