CHLORINE ANALYTIC METHOD IN COATED FILM OF STEEL PLATE

PROBLEM TO BE SOLVED: To provide a method of easily precisely analyze chlorine in a coated film formed on a steel plate.SOLUTION: A chlorine analytic method comprises: a step 1, in which a coated film on a steel plate is resolved by an alkaline solution containing neither Ag ion nor ions forming poor solubility salt; a step 2, in which Ag is added to the solution into which the coated film is resolved by step 1 and chlorine is made to precipitate from the solution as silver chloride; a step 3, in which the silver chloride precipitated by step 2 is isolated from the solution; a step 4, in which the isolated silver chloride by step 3 is resolved again; and a step 5, in which a quantity of resolved Ag in the solution by step 4 is determined and an amount of chlorine is calculated.