本法是用卑磷酸盐在酸性溶液中,将锡(Ⅳ)还原成锡(Ⅱ)状态,然后以碘滴定。吸取过滤的槽液5毫升,置于500毫升锥形瓶中,加水150毫升、浓盐酸(1.18)60毫升,加卑磷酸钠(或卑磷酸钙)15毫升,二氯化汞0.2～0.3毫克。塞上有玻璃导管的橡皮塞。导管一端插入碳酸氢钠饱和溶液中(普通的定碳装置),加热还原,沸腾后保持2～3分 This method is the use of hibiscus acid in acidic solution, the tin (Ⅳ) reduced to tin (Ⅱ) state, and then titrated with iodine. Pipette 5 ml of filtered solution into a 500 ml Erlenmeyer flask and add 150 ml of water, 60 ml of concentrated hydrochloric acid (1.18), 15 ml of sodium hypophosphate (or calcium hypophosphate), 0.2 to 0.3 mg of mercuric chloride . Stuffed with glass catheter rubber plug. One end of the catheter is inserted into the saturated solution of sodium bicarbonate (ordinary carbon fixation device), heated to restore, keep 2 to 3 after boiling