DETERMINATION OF MICRO AMOUNT OF ARSENIC IN HIGH-PURITY TUNGSTEN TRIOXIDE BY COPPER REAGENT SILVER METHOD

After As in WO3 is dissolved with NaOH solution, WO3 is coordinated by citric acid. In HCl medium, As is reduced to lwo valency As by KI and then low valency Asis reduced to gas AsH3 by SnO2 and metal Zn. After that, DDTC-Ag solution is applled as absorbent for colorimetric determinhtion. This method is simple, accurate and its determination range can reach 0.000 8%~ 0. 020 0%. The relative standard deviation is ±5. 9% and recovery lies between 94 % ~ 106%. It is suitable for the determination of micro amount of As in tungsten trioxide, tungstenic acid and secondary ammonium tungstate.