Über die Trennung der seltenen Erden durch basische Fällung. (I)

The Basicity Characteristics of Scandium, Yttrium, and the Rare Earth Elements.

“…Thus, while dehydration experiments show that lanthanum (186), praseodymium (428), and neodymium (428) yield hydrous hydroxides, yttrium and samarium (428) hydrous oxides, and scandium (428) a hydrous monohydrate, corresponding data are not available for the remaining elements. While basic salts undoubtedly separate first in many alkali precipitations (343,376), at least some of the other elements appear to form hydrous hydroxides under these conditions (144). Regardless of the nature of the hydrous material precipitated, its precipitation involves the consumption of hydroxyl ions and is, therefore, related to the basicity of the element in question.…”

“…Most observations on the relative solubilities of the oxides or hydrous precipitates in acidic solutions have been only qualitative, although Brauner (45) early pointed out that the solubilities in aqueous ammonium nitrate solution of Di205, Di203, and La203 were in the ratio of 1 to 10 to 29. More recently Prandtl and coworkers (335,342,343,344,345,346) have measured the solubilities of a number of hydroxides in ammonium salt solutions in the presence and absence of cations forming ammonia complexes. (and basicity increases) in the order yttrium, samarium, neodymium, praseodymium, lanthanum.…”

“…Solubility-product constants have been calculated from titration data by Sadolin (361), Oka (327,328), and Moeller and Kremers (297), upon the assumption of the ultimate precipitation of hydrous hydroxides in all instances. That basic salts actually form in such reactions is well known (343), but the method is still useful particularly for comparisons of the freshly precipitated materials. Latimer (240) has also estimated solubility-product constants for the hydroxides of lanthanum, yttrium, lutecium, and scandium from available electrochemical data.…”

“…As experimental evidence for the relatively high basicities of the oxides of these elements, one can cite the ease with which even the strongly ignited oxides of all but scandium dissolve in acids (66,79,250,263,285,305,416); dissolve in ammonium salt solutions with the liberation of ammonia (20,21,45,244,250,263,343); dissolve in aniline hydrochloride solutions (233); react with such hightemperature acids as ammonium salts (5,146,147,181,351,352,394,450), borax (31,154), metaphosphate (31), and alkali bisulfate (231,363) or pyrosulfate (11, 212); and absorb atmospheric carbon dioxide (114,250,263,278,285). To these can be added the comparatively high water solubilities and precipitation pH values of the hydrous oxides and hydroxides (64,65,74,167,222,297,327,361,389,398), the tendencies of at least some of the oxides to slake with water (244, 250, 278, 285), the absorption of carbon dioxide by hydrous lanthanum (12,...…”

Coordination Through Nitrogen of the Donors

“…Prandtl and Rauchenberger (33) have pointed out that the addition of ammonia to an aqueous solution of rare-earth chlorides pre cipitates the practically insoluble rare-earth hydroxides and an equilibrium of the type…”