抄録
Sodium dithionite is used for the iron removal in clay industry, because this reducing agent is easy to handle and has strong reducing action.
On the removal of iron oxide from clays with sodium dithionite-sulfuric acid solution (pH2-3), the reducing agent is used not only for the reductio n of Fe3+to Fe2+but for the reaction with atmospheric oxygen and the self-decomposition reaction, therefore it is necessary to determine effective conditions of the reduci ng reaction.
But the reducing reaction is very rapid, it is difficult to pursue the process of the reaction with chemical analysis.
In this experiment, the removal reaction of iron oxide from “Ohata” clay with sodium dithionite-sulfuric acid was investigated with the changes of oxidatio n-reduction potential, pH and the amount of dissolved oxygen.
Following results were obtained.
1) Sodium dithionite was used for the reaction with atmospheric oxyge n and the self-decomposition, and the reduction ability was lost above-200mV (Pt-s. c. e.) of the oxidation-reduction potential.
2) The changes of pH and the amount of dissolved oxygen were correlati ve with the change of oxidation-reduction potential.
3) The dissolved iron ions were ferrous state, and the change of Fe2+to Fe3+was begun when the change of oxidation-reduction potential became little.
