The amount of the fixing agent to be used can be properly altered but isnormally from 0.1 mol/l to 5 mol/l.The water-soluble aluminum salt which serves mainly as a film hardener in the fixing solution is a compound known as a film hardener for acidic film-hardening fixing solution, such as aluminum chloride, aluminum sulfate and potassium alum.As the dibasic acid, tartaric acid, citric acid or a d