系统研究了反应时间、水温、显色剂的用量及pH对游离性余氯测定影响，优化选择最佳操作条件:控制水样pH<8，水温25℃，显色剂用量25mL，加入显色剂后立即比色，测定游离性余氯。在此条件下，测定三种生活饮用水游离性余氯，回收率在96.7%～99.8%，测定结果与《生活饮用水标准检验法》37.3滴定法颇为一致。

All factors affecting the determination of free residual chlorine have systematically studied. In addition, the best opera tional conditions have been optimized. Under these conditions, the recovery rate of the free residual chlorine in three water samples are 96.7% to 99.8%. These result s are very consistent with Drinking Water Standardized Testing Method 37.3-Tit rimetric Analysis.