The Ionic Effect of Se and Te on the Stability of Thiosulfate

概要

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A large number of studies have been carried out for the stability of thiosulfate in fixers. In generally, thiosulfate is very stable in the nutral and alkaline solution, but it has a tendency to decompose spontaneously free sulfer and sulfuric acid in an acidic solution. The decomposition of thiosulfate has been considered the following equation. Na_2S_2O_3→Na_2SO_3+S↓ The mechanism of this reaction is not so simple, that many investigations has been concerned in it. In these experiments the authers find out that the decomposition times of thiosulfate solution may be prominently decreased by adding very small amounts of impurities such as Se or Te ions. The commercial base thiosulfate usually contains a trace amounts of elements of Se and Te. Even if the slightest amounts of contaminants, such as Se and Te, are contained in the fixer, a remarkable stimulation of an oxidative reaction goes on progressively. In geneneral, the complete separation of an element of the homologous series is very difficult since their chemical properties resemble one another comparatively. Based on the facts which have been clarified so far, we are considering synthetically, the way to progress with our study hereafter.
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