Chromium is oxidized by ammonium persulphate, and measured by ferro - titration.Tungsten is measurde in concentrated sulphuric acid by benaenedid photometry.

• 铬用过硫硫铵银盐氧化、亚铁滴定法容量法，利用对苯二酚光度法，在浓硫酸介质中对钨测定。