Determination of Arsenic in White Metals by Distillation-Coulometric Iodometric Titration

Distillation-coulometric iodometric titration was developed for arsenic determination in white metals based on Japanese Industrial Standard (JIS), which is composed of a two-times distillation of arsenic. Since the recovery of arsenic by the first distillation was 86%, analytical procedures were improved, as described. The addition of water to decomposed the sample solution was reduced, and the first distillation was done for 30 min at 105℃ of vapor temperature, followed by the addition of HCl and FeSO4·7H2O and distilling similarly for 20 min. By using the improved procedures, the recovery was 99.9% and the time required for sample preparation was reduced to half. Separated arsenic(III) was then titrated with electrogenerated iodine. The end points of the titration were detected amperometrically. The coulometric assey of a white metal reference material (certified value 0.088%) was 0.086% with a relative standard deviation of 0.37%.