XCVII.—Contributions to the chemistry of thoriums; comparative research on the oxalates of the rare earth

Abstract

IN continuing my researches on the chemistry of the '' rare earth "

The Analytical Aspects of Thorium Chemistry.

“…These procedures are usually sufficiently quantitative in character to permit their application without essential modification. Perhaps the best general separational method involves precipitation of thorium with oxalic acid from slightly acidic solutions (37,109,224). Oxalate precipitation is effective not only in separating thorium from all the common metals but in removing phosphate as well.…”

“…While several repetitions of the procedure were required, Bunsen found it to work to advantage upon thorium compounds which had been precipitated previously with sodium thiosulfate (48). The basis for the method is apparent in the relative solubility data for thorium and rare earth oxalates in excess ammonium oxalate solution as given by Brauner (36,37). Expressed in terms of the relative quantities of oxides dissolved, these solubilities were determined to be: Th, 2663; Yb, 105; Y, 11.0; Ce(III), 1.8; Nd, 1.5; Pr, 1.2; and La, 1.0.…”

“…The composition of the complex oxalate derivative existing in solution has not been determined with accuracy. Brauner (36,37) reported that 3.59 moles of oxalate ion were required to keep each mole of thorium in solution and suggested the formula (NH4)2C204 • 2Th(C204)2 • 7H20 for the product crystallized from such solutions. Both this compound and a dihydrate were obtained by James, Whittemore, and Holden (130), and Hauser and Wirth (106) postulated the existence of the complex [Th2(C204)5] • That the oxalate procedure effected only an incomplete separation of thorium from the rare earth elements and yttrium was recognized early (131), although Hintz and Weber (121, 122) found the method to be superior to that involving thiosulfate on a comparative basis.…”

“…From its solution in ammonium oxalate, thorium may be recovered by precipitation with acids (36,37,121), by precipitation with ammonia (99, 121), or by evaporation and ignition to oxide (47, 48). Zirconium oxalate is extracted with thorium oxalate but does not precipitate on acidification (55, 127, 128), while the major portion of dissolved yttrium earth oxalates is precipitated by dilution (47,48,224).…”