Preparation of Rare Earth Bromates

The solution of rare earth sulfates (about 3.5 1.) is now added with prolonged stirring to 4.1 kg. of freshly prepared solid barium bromate (synthesis 6) in an evaporating dish. The mixture is heated and stirred, and further small amounts of barium bromate are added, if necessary, imtil a sample gives no further precipitation with a solution of the latter reagent. The barium sulfate and any excess barium bromate are then removed by filtration, and the solution is carefully evaporated on a steam bath until a small sample crystallizes almost completely when it is allowed to cool. Any small amount of barium bromate that crystallizes during the evaporation may be allowed to remain, as it is easily removed later at the less soluble end of the fractional crystallization series. 

The mixed rare earth bromates are obtained in the form of colorless or faint-pink needlelike or feathery crystals. They are moderately soluble in cold water and very soluble in hot. The minimum in solubility among the various earths occurs at europium although the position of this minimum depends upon the crystallization temperature. 

Since the bromates tend to form highly supersaturated solutions, no fractions should be completely dissolved during the dissolution operation in fractionation otherwise, when crystallization occurs, either by agitation or by sudden 

The rare earth bromates are relatively stable in the absence of cerium or other reducing materials. Very little thermal decomposition occurs if overheating of the crystals and of the solution is avoided. To avoid such decomposition, the fractions should be heated carefully always on the steam bath and should be regularly mixed by gentle swirling during this operation. 

Separation of Europium prom Rare Earth Mixtures 

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