rpHH separation of thorium from the rare earths, particularly in -* monazite, is of great interest. Previous work on the subject has been critically reviewed by XX'illard and Gordon (11), who also describe an elegant method for the decomposition of monazite and the estimation of thorium therein. Reference may also be made to a later communication by Gordon, Vanselow, and Willard (£). Several reagents have been under investigation in this laboratory (4, 9, 10). Organic reagents present the advantage that the precipitate is voluminous and enable small quantities of the metal ion to be handled convenient!!". m-Cresoxyacetic acid, which is described here, gives with as little as 2.0 mg. of thorium oxide a precipitate large enough for easy handling. The precipitate has a varying composition and cannot be weighed directly, but this difficulty is overcome by igniting to the oxide.
D EAGENTS for the determination of zirconium are many, but *few are selective. The best known is mandelic acid, recommended byKumins (£). To this may be added m-cresoxyacetic acid,•-0-CH2COOH, a reagent that is easily pre-CH3 pared and purified (I). From solutions 0.20 to 0.25 N in hydro-
Fumaric acid precipitates zirconium completely from solutions up to 0.35 N in hydrochloric acid. The precipitate, which has the approximate composition O = Z r = X (where X stands for the fumarate radical), is gelatinous; i t is ignited to give the oxide.From solutions 0.25 N in hydrochloric acid the reagent separates zirconium from aluminium, beryllium, uranium, nickel, barium, calcium, iron, manganese, thorium and the ceria earths in a single precipitation; vanadium, chromium, titanium, and tin are completely removed in a double precipitation. Zirconium has also been estimated in zircon.
CHEMICAL LABORATORIESANDHRA UNIVERSITY TVALTAIR, s. INDIA
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