PURPOSE:To measure the concentration of silver of a fixing agent with high accuracy, by allowing ClO- ion to exist in a silver ion solution in which thiosulfuric acid salt coexists, under an alkaline state and forming slightly soluble silver salt by oxydizing thiosufuric acid ion and measuring the concentration of silver by absorptiometry. CONSTITUTION:At the time of measuring the concentration of silver in a solution in which thiosulfuric acid salt such as a fixing agent coexits, a bleaching fixing agent, thiosulfuric acid is oxidized to SO4 by adding NaClO solution and adding NaCl, in necessary, in an alkaline state obtained by adding an aqueous solution of KOH and K2HPO4. The absorbance of AgCl produced by the reaction of NaCl silver ion in 670nm wavelength is measured by using a glass cell of 10m/m light passage length. The concentration of silver is measured quickly and simply with high accuracy by using a calibration curve measured by the silver solution of preliminarily know quantity.
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