From summary: "The influence of the structure of phosphate esters on the distribution coefficient of uranium between solutions of these esters in carbon tetrachloride and aqueous nitrate solutions has been studied. Esters of secondary alcohols showed higher distribution coefficients than primary alcohols. Phenyl esters extracted less uranium than alkyl esters, and the presence of other negative groups also resulted in less extraction. Compounds containing carbon to phosphorus bonds gave higher distribution coefficients than the corresponding esters, and the distribution coefficients increased with the number of such carbon to phosphorus bonds. Tributyl phosphine oxide (with three carbon to phosphorus bonds) showed high distribution coefficients with many salts, including uranyl nitrate, uranyl sulfate, uranyl chloride, thorium nitrate, plutonium (IV) nitrate and some of the fission products in nitrate solution. It is planned to study these and similar compounds further."