我们在用抗坏血酸作还原剂、硫氰酸盐比色测定钢铁中钼的试验工作中,发现正确选择参比溶液是一个值得注意的问题。冶金部《钢铁化学分析方法》(YB35(1—28)-78)、以及成文、慧敏等编写的《合金钢化学分析》一书中比色法测定钼,皆以不加硫氰酸盐的不含钼的试液或对应试液为参比。这样处理,未考虑抗坏血酸不能把3价铁全部还原成2价,“残余”的3价铁与硫氰酸盐生成有色络合物干扰测定的问题。上海第一钢铁厂中心试验室、上海师范大学化学系合编的《钢铁化学分析》一书中比色测定钼的方法,以加硫氰酸盐的试剂空白溶液为参比测定系列标准溶液的吸光度,以不加硫氰酸盐的试液为参比测量显色试液的吸光度。这种将“试剂空白”与“试样空白”不统一处理的办法,会给结果带来误差。我们建议称取与试样同样量的纯铁、标钢,按分析步骤溶样、稀释、分取,按级差加入不同量钼标准溶液,然后加入同样量的硫氰酸盐显色剂,以水为参比分别测量纯铁、试样、标 We used ascorbic acid as a reducing agent, thiocyanate colorimetric determination of molybdenum in steel work, found that the correct choice of reference solution is a noteworthy issue. Metallurgical Department “method of chemical analysis of steel” (YB35 (1-28) -78), and written, Hui Min and other prepared “chemical analysis of alloy steel,” a book colorimetric determination of molybdenum, all without thiocyanate Of the non-molybdenum-containing solution or the corresponding reference solution. In this way, the problem that the ascorbic acid can not completely reduce the ferric iron to the divalent metal and the “residual” trivalent iron and the thiocyanate produce a colored complex interfere with the determination. Shanghai First Steel Works Center Laboratory, Shanghai Normal University, Department of Chemistry, edited by the “Steel Chemical Analysis” book colorimetric determination of molybdenum, thiocyanate reagent blank solution as a reference to determine the standard solution Absorbance, with no thiocyanate test solution as a reference measure the absorbance of the color test solution. This will “reagent blank” and “blank sample” approach will result in errors. We suggest to weigh the same amount of pure iron and standard steel as the sample, dissolve it according to the analysis steps, dilute it, separate it, add different amount of molybdenum standard solution according to the difference, then add the same amount of thiocyanate color reagent to Water as the reference were measured pure iron, sample, standard