称取试料(200目以下)0.2g于400ml烧杯中,加无水硫酸钠2g,浓硫酸10ml,低温溶解,逐渐升高温度,当冒烟时,盖上表皿,溶解完全为止(体积最后5ml为宜)。稍冷,洗净表皿及杯壁,体积约30ml,此时钨酸析出。加氯化钠3g,用40%氢氧化钠中和至清后,再滴加至刚出现蓝色(有时不出现蓝色),pH控制在13～13.5。 Weigh the sample (200 mesh or less) 0.2g in 400ml beaker, add anhydrous sodium sulfate 2g, concentrated sulfuric acid 10ml, dissolved at low temperature, and gradually increase the temperature, when smoking, cover the table, dissolved completely until The last 5ml is appropriate). Slightly cold, wash the watch glass and cup wall, the volume of about 30ml, when tungstic acid precipitation. Add sodium chloride 3g, neutralized with 40% sodium hydroxide to clear, and then added dropwise until just blue (sometimes does not appear blue), pH control in 13 ~ 13.5.