目前钢铁中铋的测定一般采用碘化钾-马钱子碱萃取光度法。此法灵敏度较低,且马钱子碱有毒。我们试验用罗丹明B,在0.6～0.9N的硫酸介质中,使其与碘铋络离子生成离子缔合物。它具有灵敏度高和不需萃取的优点。20℃时,ε=1.05×10~5。但也存在着温度对色泽的影响较大的缺点。温度和吸光度有一定的比例关系,可作适当的温度校正。本方法用在实际分析中还是可行的。一试剂碘化钾溶液:20%(内含抗坏血酸0.5%); 铋标准溶液:称取0.1000克纯铋,加入硝酸(1+1)20毫升溶解,蒸发至近干,加入硫酸(1+6)30毫升溶解,煮沸,冷却,移入1000毫升量瓶中,用硫酸(1+8)稀至刻度,摇匀。吸取此溶液5毫升, The determination of bismuth steel commonly used potassium iodide - strychnine extraction spectrophotometry. This method is less sensitive, and strychnine toxic. We experiment with rhodamine B, in 0.6 ~ 0.9N sulfuric acid medium, make it with iodine bismuth complex ion association. It has the advantages of high sensitivity and without extraction. At 20 ° C, ε = 1.05 × 10 -5. But there is also the temperature on the color of the larger disadvantage. Temperature and absorbance have a certain proportion, can be used for temperature correction. This method is still used in practical analysis. A reagent potassium iodide solution: 20% (containing ascorbic acid 0.5%); bismuth standard solution: Weigh 0.1000 g of pure bismuth, nitric acid (1 + 1) 20 ml dissolved and evaporated to near dryness, Dissolved, boiled, cooled and transferred to 1000 ml volumetric flask, dilute to volume with sulfuric acid (1 + 8) and shake well. Draw this solution 5 ml,