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用自动控制ｐＨ的装置定量研究了两种红壤类土壤胶体在三种中性盐溶液中的交换性碱和交换性酸的变化。发现在Ｎａ_２ＳＯ_４溶液中在ｐＨ低时出现交换性碱，ｐＨ高时出现交换性酸。砖红壤胶体的交换性碱比红壤胶体的大，并且在ｐＨ５．６附近还出现不受Ｎａ_２ＳＯ_４浓度影响的交换中性点。ＮａＣｌＯ_４和ＫＣｌＯ_４溶液中，在测定ｐＨ范围内只出现交换性酸，红壤胶体的数量比砖红壤胶体的大。同一土壤胶体在ＫＣｌＯ_４中的数量比ＮａＣｌＯ_４中的多。二者都有一峰值，对于砖红壤胶体前者在ｐＨ４．３，后者在ｐＨ５．８。提出了测定ＳＯ４２－－交换性碱的方法。
The changes of exchangeable alkali and exchangeable acids in two kinds of neutral salt solution were quantitatively studied by means of automatic pH control. An exchangeable base was found at low pH in Na 2 SO 4 solution, and an exchangeable acid appeared at high pH. The exchangeable alkali of brick red soil colloids is larger than that of red soil colloids, and the exchange neutral point which is not affected by the concentration of Na_2SO_4 also appears near pH5.6. In NaClO_4 and KClO_4 solutions, only the exchangeable acid appeared in the pH range of the determination, and the amount of red soil colloids was larger than that of the latosol red soil colloids. The same amount of soil colloids in KClO_4 than in NaClO_4 more. Both had a peak at pH 4.3 for brick red soil colloids and pH 5.8 at the latter. A method for the determination of SO42 - exchangeable base was proposed.