Bismuth(III) (0-25 mug/ml) is determined spectrophotometricaly at 513 nm after extraction into dichloromethane of the ion associate di-(hydrogenatedtallowalkyl)dimethylammonium tetraiodobismuthate. The reagent stream is distilled water, merged with 1.0 M sulfuric acid, 5% potassium iodide and 5% (w/v) ascorbic acid solution. The reagent stream is 0.2% (w/v) di-(hydrogenatedtallowalkyl)dimethylammonium chloride solution. The injection rate is 15 h(-1). The calibration graph is linear up to 25 mug/ml. The detection limit is 0.35 mug/ml Bi. The system is applied on water samples and copper-based alloys.