| 摘要 |
PURPOSE:To prepare a bleach-fix bath of high concn. and make unnecessary a harmful substance causing trouble about environmental pollution by feeding solid alkali metal salt of ferric ethylenediaminetetaacetate as a bleaching agent to a bleach-fix bath and adding a specified amount or more of NH4<+>. CONSTITUTION:To a bleach-fix bath are added solid powder or granules of sodium salt of ferric ethylenediaminetetraacetate as a bleaching agent in the form of solid matter or aqueous slurry. In order to maintain the pH of the bath at 6.5 or less a soln. of ammonium thiosulfate, ammonium hydrogensulfite or NH4OH is added so that NH4<+> is contained in an amount not less than 2.5 times as much as the total amount of Na in the above-mentioned sodium salt and Na in other components of the bath. Thus, the salt is thoroughly dissolved in a high concn. of 120g/l or more, and harmful thiocyanate or the like is made unnecessary. |
