研究了２－乙基己基膦酸单２－乙基己基酯（ＨＥＨＥＨＰ，ＨＡ）在不同稀释剂与硝酸盐水相间的分配及其在这些体系中萃取Ｆｅ（Ⅲ）的分配平衡，发现ＨＥＨＥＨＰ在两相间的分配随稀释剂极性增强而增强，Ｆｅ（Ⅲ）的分配则随稀释剂极性增强而减弱．ＨＥＨＥＨＰ与Ｆｅ（Ⅲ）形成Ｆｅ（ＮＯ３）Ａ２·２ＨＡ和ＦｅＡ３·３ＨＡ两种萃合物，稀释剂极性对后者萃取平衡常数的影响较前者明显．这些现象与被萃物种极性的不同因而使得其萃取过程的溶剂化自由能不同有关． The distribution of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEHEHP, HA) between different diluents and nitrate aqueous phase and their equilibrium distribution of Fe (Ⅲ) in these systems were studied. The phase distribution increases with the increase of the polarity of the diluent, and the distribution of Fe (Ⅲ) decreases with the increase of the polarity of the diluent. HEHEHP and Fe (Ⅲ) form Fe (NO3) A2 · 2HA and FeA3 · 3HA two kinds of extracts, the diluent polarity of the latter extraction equilibrium constant than the former obvious. These phenomena are different from those of the species being extracted, thus making their extraction process different from solvation.