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测定土壤阳离子交换量(CEC)的硫脲银(AgTU)法,包含着硫脲银土壤提取液中 Ag 的定量测定。用原子吸收分光光度计或放射性同位素和闪烁计数器很容易测定其中的 Ag。然而,很多发展中国家的土壤分析实验室,常常难以得到这种仪器。因此,研制了一种测定 AgTU 土壤提取液中 Ag 的简单方法。该法包括用浓度为5×10~(-4)～10~(-2)克分子/升的 AgTU 溶液校准过的、稳定的蒙脱石悬液的稳定性终点滴定过程。用这种粘粒滴定法测定的硫脲银——阳离子交流量(AgTU-CEC)与用 NH_4OAc 和 KCl 提取测定的“有效的”阳离子交换量及用原子吸收分光光度计测定的 AgTU-CEC 相比,其相关系数分别为0.95和0.97。
The thiourea silver (AgTU) method for the determination of soil cation exchange capacity (CEC) includes the quantitative determination of Ag in thiourea silver soil extract. Ag is easily measured by atomic absorption spectrophotometer or radioactive isotope and scintillation counter. However, soil analysis laboratories in many developing countries often find it difficult to obtain such instruments. Therefore, a simple method for the determination of Ag in AgTU soil extract was developed. The method includes the stability titration of the stable montmorillonite suspension calibrated with AgTU solution at a concentration of 5 × 10 -4 to 10 -2 mol / L. The thiourea silver-cation exchange (AgTU-CEC) measured with this cosmid titration method was compared with the “effective” cation exchange capacity measured with NH4OAc and KCl extraction and the AgTU- CEC, the correlation coefficients were 0.95 and 0.97 respectively.