Contributions to the rare earths to science and technology

This is a brief summary of some areas of science where the rare earths have already played an important role and of other areas where they are almost certain to be helpful. The discovery, abundance, separation, and properties of rare earths are discussed. It is pointed out that the rare earths comprise almost one-fourth of the known metals, and their alloys a third of the possible alloys. (DLC

BASIC PRINCIPLES INVOLVED IN THE MACRO-SEPARATION OF ADJACENT RARE EARTHS FROM EACH OTHER BY MEANS OF ION EXCHANGE

BS>The separation of rare earth mixtures by ion exchange using ammonium ethylenedisminetetracetate and annmonium N-hydroxyethylethylenediaminetriacetate as eluting agents is discussed in detail. Simple countercurrent separation theory is used to predict the minimum nuinber of displacements of an adsorbed band that are necessary in order to separate the components of binary mixtures. It is shown how the theory can be applied to even more complex systems, and experimental data are presented for some of the more difficultly separablc groups of rare-earth species. Experimental results agree very well with the theoretical predictions. (auth) A detailed description is presented of a process developed by Ames Laboratory for the separation of thorium, rare earths, and uranium from monazite sands. Oxalic acid is used to precipitate rare earths; and thorium from a sulfate and phosphate solution of these elements. The possibility of recovering uranium from the oxalate filtrate by anion exchange was investigated. (W.L.H.

THE HIGH TEMPERATURE HEAT CONTENTS AND RELATED THERMODYNAMIC PROPERTIES OF LANTHANUM, PRASEODYMIUM, EUROPIUM, YTTERBIUM, AND YTTRIUM

The high temperature enthalpies of five rare earths were measured from 0 to 1100 deg C using a Bunsen ice calorimeter. The enthalpy of yttrium metal was studied from 1100 to 1675 deg C using a modified high temperature vacuum Bunsen calorimeter. The data were fitted to empirical equations from which the heat of transition and fusion, the heat capacity, and the related thermodynamic quantities were calculated. These results confirmed indications from other properties that europium and ytterbium metals are primarily in the divalert state. Small anomalies observed in europium and ytterbium were attributed to transitions between electronic states when some trivalent ions occur in these metals. The ertropy of the fcc-bcc transition for ytterbium was found to be approximately two- thirds that of the other rare-earth metals for which a close-packed to bodycertered cubic transformation was observed. (auth