HIGHLY HYDRATED ASSOCIATE OF TRIBUTYL-PHOSPHATE IN DODECANE

The hydration and association of tributyl phosphate (TBP) in dodecane were investigated on the basis of the water distribution between aqueo us solutions and TBP-dodecane solutions at 298 K. The water distributi on data were analyzed as functions of the TBP concentration in the org anic phase and the water activity in the aqueous phase. A highly hydra ted TBP trimer was found in the organic phase at high TBP concentratio ns by the data analysis. At [TBP]org,total less-than-or-equal-to 0.02 mol dm-3, no TBP association occurred and only TBP-H2O formed as a uni que hydrate. In the range of 0.02 mol dm-3 < [TBP]org,total less-than- or-equal-to 0.3 mol dm-3, a part of the monohydrate dimerized to form (TBP)2(H2O)2. At [TBP]org,total > 0.3 mol dm-3, trimerization also occ urred at high water activities. The trimer was found to be hydrated wi th six water molecules, (TBP)3(H2O)6.