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采用氟化铵作为交换液,将土壤样品中可交换阳离子钾、钠、钙、镁、铝等离子交换出来,交换10 min后进行过滤分离,吸取滤液10 mL到凯氏瓶,加入过量NaOH蒸馏,将多余的铵根离子转化为氨气,用硼酸吸收液吸收,稀盐酸滴定,根据铵根离子的减少量计算土壤中阳离子交换总量。该方法可操作性强,且操作流程短,精密度RSD值小于4.5%,相对误差RE小于7%,可满足土壤样品中阳离子交换量的分析要求。
Ammonium fluoride was used as exchange solution to exchange the exchangeable cation potassium, sodium, calcium, magnesium and aluminum ions in the soil sample. After exchange for 10 min, the filtrate was separated by filtration and 10 mL of the filtrate was taken to Kjeldahl bottle. After excess NaOH was distilled off, The excess ammonium ion is converted to ammonia gas, absorbed with boric acid absorption solution, dilute hydrochloric acid titration, according to the reduction of ammonium ions to calculate the total amount of cation exchange in the soil. The method has strong operability and short operation flow. The precision RSD value is less than 4.5% and the relative error RE is less than 7%, which can meet the analytical requirements of cation exchange capacity in soil samples.