The work here discussed represents part of the investigations of the rare earths which are being carried on in the laboratory of Inorganic Chemistry of the University of Illinois. One object of the ...present work was to study some separation methods which might be suitable for the isolation of the various individual earths, more particularly those of the yttrium group. This was undertaken preliminary to a later object which was to prepare dysprosium material of sufficient purity for atomic weight work, and to determine the atomic weight of that element. Oxides of the rare earths obtained from a previous investigation (Egan and Balke, J. Am. Chem. Soc., 35, 365. 1913) furnished most of the material for this work. These were originally obtained from the following mineral sources; monazite, gadolinite, xenotime, euxenite, and fergusonite. From the gadolinite and xenotime material part of the yttrium had been previously removed in the investigation above referred to. The oxides were, in the main, those of the yttrium earths, though some portions contained appreciable quantities of the cerium earths.
