Polarographic Determination of Tin in Lead Alloys

It was reported that major and minor amount of tin in lead alloys were determined by polarography in testing solution containing 4 mL of H2SO4 (1+1) and 10 drops of 2 g·L-1 methylene blue solution, and diluting to a definite volume of 50 mL with 32 g·L-1 oxalic acid solution. Anodic scanning at the rate of 500 mV·s-1 and 2nd derivative of the measured polarographic wave were adopted in the determination. The sample (0.100 0 g) was dissolved in distilled water (10 mL), tartaric acid (2 g) and HNO3 (3-4 mL), and Pb2+ was separated by addition of H2SO4 (1+1) (5 mL). Five drops of 100 g·L-1 BaCl2 solution were added to separated Pb2+ completely as compound sulfate precipitate. Linear relationship between values of peak current and mass concentration of Sn was obtained in the range within 20.0 mg·L-1. 7 samples of lead alloys were analyzed by the proposed method for their tin contents, giving results consistent with the known values, and RSD′s (n=6) found were less than 6%.