Alkaline earth cations, effect precipitation

The rare earths can be precipitated as the hydroxides, but because of the relatively large difference in the basicity in the rare earths this is not an effective method for the separation of the rare earths from any elements except the alkali and the alkaline earth cations. The precipitate is bulky, amorphous and difficult to filter. The light lanthanides are quite basic and lanthanum is not completely precipitated at a pH less than 10. Precipitation of the rare earth hydroxides is sometimes a useful procedure for the preliminary separation of small amounts of the rare earths from solutions in which the concentration of a number of other elements is high. The hydroxide precipitate is most conveniently separated by centrifugation, redissolved and the rare earths precipitated as the oxalates. 

The present review deals mainly with two examples of polyelectrolyte phase behavior as discussed above. As an example for an H-type precipitation, the solution properties of polyvinylpyridinium chains are monitored as function of added inert salt. Here, we focus on the determination of the effective charge density and of the solvent quality parameter which are supposed to play a central role for the understanding of polyelectrolyte solution without specific counterion interactions. The second system under investigation comprises the interaction of polyacrylic acid with alkaline earth cations which exhibit very specific interactions, thus representing an example for type L-precipitation. Here the coil dimensions close to the phase boundary are compared to those close to type H-precipitation with inert added salt. 

EQCM studies also provided useful information on the C60 film dissolution/precipitation effects in the presence of alkali and alkaline earth metal cations [142,157]. Koh etal. [157] started with Qq solutions in different electrolytes. They found no mass increase when was either reduced to the C6o or... 

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