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四苯硼钠容量法测定钾,以往常用二甲酚橙或PAN指示剂、锌标准液回滴。由于滴定终点不敏锐,致使误差较大。本文改用高灵敏显色剂5-Br-PADAP为指示剂、铋标液回滴。则滴定终点非常敏锐,可用于铝土矿烟尘中0.5～30％氧化钾的测定。分析步骤:称取0.2000克试样于塑料坩埚中,加0.5毫升硫酸(1+1)、6毫升氢氟酸加热溶解并蒸发冒烟3分钟,冷却,加1毫升盐酸(1+1)和20毫升水,煮沸使盐类溶解,冷却移入100毫升容量瓶中,加水至刻度。
Sodium tetraphenylboron volumetric method for the determination of potassium, xylenol orange or PAN indicator used in the past, zinc standard solution back drop. As the titration end is not sharp, resulting in greater error. This switch to highly sensitive reagent 5-Br-PADAP as indicator, bismuth standard solution back drop. The titration end point is very sensitive and can be used for the determination of 0.5-30% potassium oxide in bauxite dust. Analysis steps: Weigh 0.2000 g sample in a plastic crucible, add 0.5 ml of sulfuric acid (1 + 1), 6 ml hydrofluoric acid dissolved by heating and evaporation 3 minutes, cooled, add 1 ml of hydrochloric acid (1 +1) and 20 ml of water, boiled to dissolve salts, cooled into 100 ml volumetric flask, add water to the mark.