GB952499A - Preparation of thorium oxalate - Google Patents

Abstract

Thorium oxide of high packed bulk density is made by calcining thorium oxalate in either the dihydrate or hexahydrate form, which is prepared by the process of the invention (see Division C2), and which has a packed bulk density of at least 1.0 gms. per c.c. The preferred temperature for calcining the dihydrate is 600 DEG C. In an example the oxide produced has a packed bulk density of 3.2 gms. per c.c. and, in a series of experiments expressed in tabular form, the oxides obtained have packed bulk densities varying from 2.0 to 3.3 gms. per c.c.ALSO:Thorium oxalate, of relatively high bulk density, is made by feeding an aqueous solution of a thorium salt, with a pH of below 4, into an oxalic acid solution to form a reaction mixture which is maintained at 40 DEG C. and upwards and adding thereto, whilst thorium oxalate is precipitated, a monovalent cation in an amount directly proportional to that of the thorium within the range of 0.5 to 15 moles of cation per mole of thorium added to the acid solution. A dense thorium oxalate has a packed bulk density of at least 1.0 gms. per c.c. Preferably the thorium solution contains at least 0.05% by weight of thorium as Th+4 and not more than 2-5 moles of cation per litre of aqueous solution and 4 to 6.5 moles of cation per mole of thorium are present. Preferably solutions containing about 10% by weight of oxalic acid are used. The cation may be added as a constituent of the aqueous thorium solution. If the hydrogen ion concentration of the thorium solution is above 10N it is partially neutralized e.g. with sodium hydroxide. Sodium, potassium, lithium and ammonium cations, and mixtures thereof, are specified. Thorium sulphate, chloride and nitrate are specified thorium salts. If the cation is added as an oxalate the cation containing, and thorium containing, solutions should be added simultaneously at a rate such that the cation to thorium ratio remains substantially constant within the above range. In an example an aqueous solution of thorium and sodium sulphate is added, at 80 DEG C., with agitation, to an oxalic acid solution, the thorium hexahydrate being filtered off and dried to form the dihydrate with a packed bulk density of 1.37 gms. per c.c. The oxalate may be calcinied to the oxide with a packed bulk density of 3.2 gms. per c.c. (see Division C1). Other salts used are sodium chloride and nitrate, ammonium chloride and sulphate, and potassium and lithium sulphate. The results of a number of experiments illustrating various changes in the reaction conditions, and salts used, are shown in tabular form, the packed bulk derivatives of the oxalates obtained varying from 1.0 to 1.37 gms. per c.c.