A New Method for the Determination of Thorium in Monazite Sand.

Chemistry of Thorium - Quantitative Estimation of Thorium by Precipitation with Radioactive Pyrophosphate

“…As found in this laboratory, the half-wave potential of the ferric-ferrous reduction was -0.94 volt with the tet.ramethyl ammonium iwdroxide solution used. This was to be expected, since half-wave potential for ferric-ferrous iron in potassium hydroxide and mannitol has been reported as -0.9 volt (3). Although it is possible that use of an oxalate medium (g) manshift the iron half-wave so that it would no longer interfere, this phase of the problem was of minor importance in this laboratory and sufficient time could not be devoted to its solution.…”

“…The pyrophosphate appears better suited to selectively precipitating thorium from yttrium and rare earth salt mixtures than does the orthophosphate. Thus, Carney and Campbell (3) found thorium to be quantitatively precipitated and removed from these elements by precipitation with pyrophosphate from solutions 0.3 .V in hydrochloric acid. It seemed logical, therefore, to base a radiometric procedure upon this observation and to use the activity of radioactive phosphorus (in the form of pyrophosphate) as a means of obtaining the thorium content of the sample.…”

The Analytical Aspects of Thorium Chemistry.

“…In systematic qualitative analysis, thorium ion is ordinarily concentrated and separated with scandium, yttrium, and the rare earth ions. After removal of scandium, thorium may be detected in the presence of the other materials by selective precipitation (26) from strongly acidic solutions with potassium iodate (186), alkali metal hypophosphates (151, 152, 209, 252), or alkali metal pyrophosphates (52) or from weakly acidic solutions with hydrogen peroxide (16,28,258,259, 260, 262), alkali metal azides (70,71, 72, 73), sebacic acid (222), m-nitrobenzoic acid (193,194,195), or sodium thiosulfate after boiling (16,77,87,121,122). Perhaps the most useful of these qualitative procedures is that employing iodate (120,186), although zirconium and cerium(IV) materials also precipitate.…”

“…SEPARATION FROM YTTRIUM AND THE RARE EARTH ELEMENTS Separation of thorium from yttrium and the rare earth elements, while not as difficult as separations among the latter elements, is, nevertheless, far from simple. The abundant literature which has accumulated on methods for such separations (24,25,26,52,120,124,163,167,175,178,183,224) may be cited as evidence for the complexity of the problem. In spite of the numerous investigations which have been carried out and of the variety of procedures which have been suggested, methods which combine rapidity with high efficiency have yet to be developed.…”

“…While cerium (IV) and zirconium pyrophosphates are also precipitated under these conditions, those of the trivalent rare earth elements are not. The method is based upon early observations on the insolubility of the thorium derivative, ThP207-2H20, by Cleve (62), and is sufficiently accurate to be adaptable to the quantitative estimation of thorium in mixtures (52).…”