What are the key production routes for high-purity arsenic and white arsenic?

What are the key production routes for high-purity arsenic and white arsenic?
High-purity arsenic is produced via two main routes. The first uses crude arsenic metal (95-99% purity) as feedstock, involving vacuum sublimation, chlorination with chlorine gas at 194°C, rectification, and hydrogen reduction. The second starts with white arsenic (As2O3, over 99% purity), which undergoes sublimation purification, dissolution in hydrochloric acid, rectification of arsenic trichloride, hydrolysis, and reduction with high-purity hydrogen. White arsenic itself is manufactured through pyrometallurgical or hydrometallurgical methods. Historically, China's Hunan Shimen realgar mine used oxidative volatilization to produce up to 5,000 tonnes per year of white arsenic. Since the 1970s, nonferrous metal smelters worldwide have adopted pyrometallurgical processes, with hydrometallurgical methods emerging in the 1980s. The choice of route depends on feedstock availability and required purity levels for semiconductor versus metallurgical applications.