EDTA滴定法によるアルミニウム合金中の亜鉛の迅速定量

抄録

Zn in the presence of Al and Sn has been titrated with EDTA. To avoid the interference of Al and Sn, NH₄F was used. The method has been successfully spplied to the determination of Zn in Al alloys. The proceduse is as follows: Weigh a 2 g sample into a beaker and dissolve it in 30 mL of 20%NaOH solution and 5 mL of 30%H₂O₂. After boiling out the excess H₂O₂, add Na₂S solution, cool, dilute to volume in a 500 mL volumetric flask and filter through a dry filter paper. Fe, Mn, Cu, Ni, Ti, Ca, Mg, etc., remain on the filter paper as hydrous oxides or sulfides. Pipet 10 to 50 mL of the filtrate into a beaker and dilute to about 70 mL with water. Make it slightly acid with HCl and 3 g of NH₄F (to mask Al and Sn) and 5 mL of 50%CH₃COONH₄ solution. Adjust the solution to pH 5 to 6 with 1 to 1 NH₄OH. Heat at 70 to 80°C, add 3 to 4 drops of indicator (PAN), mix and titrate with 0.005 M EDTA solution. Then back-titrate the excess EDTA with 0.005 M CuSO₄ solution.