Über die Trennung der seltenen Erden durch basische Fällung. VI

Abstract

In unserer zweiten und vierten Mitteilung') haben wir iiber den Einflu6 von Magnesium-, Zink-und Cadmiumnitrat auf die Fiillung der Cererden durch Ammoniak in ammoniumnitrathaltigen Losungen berichtet. Wir konnten feststellen, daB die Fiillung der Erden im gleichen Ma6e verzogert wird, als das Bindevermogen des zweiwertigen Metalles far Ammoniak in der Reihenfolge Magnesium-Zink-Cadmium wachst. Wie schon angekiindigt wurde, sollte auch der EinfluS des Endgliedes dieser Reihe, des zweiwertigen Quecksil bers, auf den Verlauf der Erdfallung untersucht werden. Wegen des bekannten besonderen Verhaltens der Quecksilbersalze gegen Ammoniak kam allerdings die Verwendung von Merkurin i t r a t nicht in Frage, da es mit Ammoniak einen in Ammoniumnitratlosung schwerloslichen Niederschlag gibt. Von allen Merkurisalzen gibt nur das Cyanid mit Ammoniak keine Fallung, bindet aber gleichwohl Ammoniak unter Bildung von Ammoniakaten und zwar auch in wasseriger Liisung; dies beweist die langst bekannte Tatsache, da6 Merkuricyanid in wiisserigen Ammoniaklosungen leichter loslich ist als in Wasser. Wir haben infolgedessen in ganz analoger Weise wie friiher die Nitrate der Cermetalle Lanthan, Praseodym , Neodym und Samarium bei Gegenwart aquivalenter Men gen Merkuricy anid nach der Gleichung 2Me"'(N0,)3 + 3Hg(CN), + 6NH, + 6 H,O G= 2M1e(0H)~ + 3Hg(CN), + 6NH,NO, in I-, 2-, 3-, 4-und 5-fach normaler Ammoniumnitratlosung bei 15O, 30°, 50° und looo mit Ammoniak zur Umsetzung gebracht und I) 2. amorg. 21. allg. Ch. 120 (1921) 120; 122 (1922) 311.

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

“…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.…”

“…An interesting series of investigations involving control of the hydroxyl-ion concentration in ammoniacal solutions through the use of ammonium salts and salts giving cations which form complex ammines has been carried out by Prandtl and his coworkers (335,336,337,339,340,342,343,344,345,346). These investigations were based upon the thesis that if the solubility of a hydrous hydroxide in the mother liquor were increased, the absolute solubility differences between neighboring materials would be magnified, and the hydroxyl-ion concentration could be so controlled that even in concentrated solutions only the least soluble material would separate (343).…”

“…Yttrium was then concentrated in the more strongly basic fractions by ammonia precipitation from 3 N ammonium nitrate solutions containing zinc nitrate along with traces of the cerium earths, gadolinium, dysprosium, and terbium (335). Experiments upon ammonium nitrate solutions containing lanthanum, praseodymium, neodymium, and samarium nitrates indicated mercuric cyanide to have about the same effect as magnesium nitrate and nickel nitrate to parallel cadmium nitrate but to be less effective (346). The effectiveness of cadmium nitrate for separations in the cerium group was approached by no other material, and a ratio of 3CdO to 1R203 was recommended (346).…”

“…Experiments upon ammonium nitrate solutions containing lanthanum, praseodymium, neodymium, and samarium nitrates indicated mercuric cyanide to have about the same effect as magnesium nitrate and nickel nitrate to parallel cadmium nitrate but to be less effective (346). The effectiveness of cadmium nitrate for separations in the cerium group was approached by no other material, and a ratio of 3CdO to 1R203 was recommended (346).…”