HB 20056.4-2011 "Sn-bismuth alloy platings and Eletroplating tin-bismuth alloy solution analysis method, Part 4: Potential Titrimetric method for the determination of stannous sulfate content" The principle, reagents, instruments, analytical steps and result calculation methods for the determination of stannous sulfate content in Eletroplating tin-bismuth alloy solution by potential Titrimetric method are specified. This part applies to the determination of stannous sulfate content in Eletroplating tin-bismuth alloy solution. Measurement range is 30g/L~ 65g/L. In the analysis process, the use of iodine solution of tin oxidation to tetravalent tin, platinum electrode and saturated Calomel electrode for Potentiometric titration, poten-tiometry, and finally calculated according to the titration results of stannous sulfate content. This standard refers to "Metal plating and chemical covering solution analysis reagents" (HB/Z5083-2001), requiring the use of reagents and instruments that meet its requirements for analysis.