Indirect complexometric determination of bismuth using 2-mercaptoethanol as masking agent

A new method for the complexometric determination of Bi in the presence of co-ions using 2-mercaptoethanol as selective masking agent has been propose d. Bismuth along with other ions in a given sample solution are initially c omplexed with excess of EDTA. The pH of the solution is adjusted to 5.0-6.0 using solid hexamine (10+/-2g) and the remaining uncomplexed EDTA is titra ted with lead-nitrate solution using xylenol orange indicator. A known exce ss of 2-mercaptoethanol solution (5% alcoholic) is then added, the mixture is shaken well and the released EDTA from the Bi(III)-EDTA complex is titra ted against standard lead-nitrate solution. The method is applied to the de termination of bismuth in Wood's alloy. Reproducible and accurate results a re obtained for 2-40 mg of bismuth with relative errors less than or equal to 0.5% and standard deviations less than or equal to 0.04 mg.