Oxydhydrate und aktive Oxyde. XLIX. Das System Lanthan(III)oxyd/Wasser

Observations on the Rare Earths. LI. An Electrometric Study of the Precipitation of Trivalent Hydrous Rare Earth Oxides or Hydroxides.

“…Working at 18°C., Sadolin (21) obtained a value of 1.2 X 10-19 for the solubilityproduct constant for freshly precipitated lanthanum hydroxide. Aged lanthanum hyrdroxide gave a constant of 1.1 X 10~21 (21), a value agreeing well with 0.91 X [10][11][12][13][14][15][16][17][18][19][20][21] reported for the aged hydroxide at 25°C. (12).…”

“…Evaluation of solubility-product constants from electrometric titration data is dependent upon a knowledge of the compositions of the precipitates ultimately produced and an assumption that the compositions of these precipitates remain essentially the same throughout the titrations (3). Even though precipitation from lanthanum salt solutions appears to be complete before the theoretical 3 OHto 1 La+4-+ mole ratio is attained, dehydration experiments have shown the precipitate to be hydrous lanthanum hydroxide (11). Similar experiments show that praseodymium and neodymium form hyrdrous hydroxides, while samarium and yttrium yield hyrdrous oxides (25).…”

Recent X-Ray Diffraction Studies on the Hydrous Oxides and Hydroxides.

“…Precipitated lanthanum oxide was found to have the composition La(OH)3 by Hüttig and Kantor (7) in 1931, using isobaric dehydration methods. Some indication of a monohydrate was observed.…”