Rare earth bromates fractional crystallization

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. 

RE(N0 )2 NH NO 4H20 for light lanthanide separation (La, Nd, Pr) 2RE(N02)3 3Mg(N03)2 24H20 for middle lanthanide separation (Sm, Eu, Gd). Bromates and ethylsulfates have been found useful. Fractional crystallization is particularly slow and tedious for the medium and heavy rare earths. 

Copper (I) iodide, 6 3 Crystallization, apparatus for, of tetrachloro (diethylene)di-platinum(II), 5 213 fractional, of magnesium rare earth nitrates, 2 52, 53 of rate earth bromates, 2 62... 

Classical methods of separation [7] are (1) fractional crystallization, (2) precipitation and (3) thermal reactions. Fractional crystallization is an effective method for lanthanides at the lower end of the series, which differ in cation radius to a large extent. The separation of lanthanum as a double nitrate, La(N03)3-2NH4N03-4H20, from praseodymium and other trivalent lanthanide with prior removal of cerium as Ce4+ is quite a rapid process and is of commercial significance. Other examples are separation of yttrium earths as bromates, RE(Br03>9H20 and use of simple nitrates, sulfates and double sulfate and alkali metal rare earth ethylenediamine tetraacetate complex salts in fractional crystallization separation. 

The cerium may now be removed from this solution by the bromate method (synthesis 14). Then the resulting solution is treated as before with excess oxalic acid or sodium suKate, the precipitates are again converted to hydrous oxides, and the latter are again dissolved in nitric acid. The rare earths from monazite are generally converted to double magnesium nitrates, 3Mg(N03)2-2(R.E.)-(N03)3 24H20 (synthesis 15), for preliminary fractionation. The rare earths from xenotime, after complete removal of cerium, may be converted to bromates (synthesis 17), and fractional crystallization of these salts may be commenced. 

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. 

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