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Crystal violet, a commercial dye, has been shown to be suitable in titrations with ceric sulphate. Its range of usefulness is great compared with tither indicators. Comparative studies on other indica­tors, viz., Xylene cyanol FF, N-phenylanthranilic acid and Rhodamine 6G are reported, extending their use to titration other than those originally recommended.

Separation of thorium from uranium by the classical oxalic acid method is not satisfactory in that the ignited oxide is slightly coloured. m-Nitrobenaoic acid and o-chlorobenzoic acid are shown to give highly satisfactory results in the presence of 50 to 60 times of uranium in a second precipitation.

Quadrivalent cerium gives a bright yellow colour with benzidine in hydrochloric acid solution. 0.03\(\gamma\) of the element can be detected on a spot-plate. Trivalent rare earths, Th, Cu, Be, Mg, alkaline earths, Zn. Al, Bi, \(UO_2^{++}\), Mn, Ni,\(NO_3^{'}\), \(PO_4^{''}\), CI', F’, MoO4", As3O4", in moderate amounts do not interfere ; but, vanadate and chromate cause interference even in small quantities. The reagent may also be adopted for the colorimetric estimation of cerium.