K_2C_2O_4-KCl法快速测定石灰性紫色土壤阳离子交换量

DETERMINATION OF CATION EXCHANGE CAPACITY IN CALCAREOUS PURPLE SOIL WITH THE K_2C_2O_4-KCl DOUBLE-QUICK EXCHANGE METHOD

用K2C2O4-KC l混合液作为交换剂,K+作为指示性阳离子,C2O42-抑制土壤中碳酸盐的溶解,采用火焰光度法测定交换后溶液中K+浓度的减少量可计算出石灰性紫色土壤的阳离子交换量。经理论计算及试验比较,K2C2O4,KC l浓度以0.03,0.02 mol/L为宜;交换剂pH、振荡时间分别为8.5,20 m in的处理得出的结果与NH4C l-(NH4)2C2O4标准方法比较回收率可达90%以上;经7次重复,变异系数<6%;结果表明该方法具有较好准确性及重复性,可以作为1种速测方法。

In this experiment, the admixture of K2C2O4-KCl was used as the exchange reagent, K^＋ as the indicatory ion and C2O4 was used to restrain carbonate from dissolving in the soil. CEC （ cation exchange capacity ） in a calcareous purple soil was calculated by determining K^＋ loss after cation exchange through flame photometric analysis. The concentration of 0.03 and 0.02 mol/L is recommended for K2C2O4 and KCl, respectively. Optimum results were achieved when pH was set at 8.5 and oscillation was kept for 20 min, in which case the recovery rate was over 90%. C.V. was less than 6% in 7 replicates. These results suggest that this method can be used as a CEC double -quick determination method.