Thorium solutions

In 1902 Rutherford and Soddy added ammonium hydroxide to a thorium solution, filtered off the thorium hydroxide precipitate, and found that, after they evaporated the thorium-free filtrate to dryness and fumed off the ammonium salts, the residue was much more active than the original thorium salt (18). This observation led them to the discovery of a new member of the thorium series, which they called thorium X. 

The bicarbonate ion, HC03, is a prevalent species in natural waters, ranging in concentrations up to 0.8 X 10 3. As was indicated previously, carbonate ions have the ability to form complexes with plutonium. Starik (39) mentions that, in an investigation of the adsorption of uranium, there was a decrease in the adsorption after reaching a maximum, which was explained by the formation of negative carbonate complexes. Kurbatov and co-workers (20) found that increasing the bicarbonate ion concentration in a UXi (thorium) solution decreased the amount of thorium which formed a colloid and became filterable. This again was believed to be caused by the formation of a soluble complex with the bicarbonate. 

Standard thorium solution 1 mg/ml. Dissolve 2.5 g of Th(N03)4.H20 in water containing 5 ml of cone. HNO3, and dilute the solution to the mark with water in a 1 -litre standard flask. Determine the concentration of thorium in the solution by evaporating an aliquot to dryness and igniting the residue in a platinum crucible at 1,000°C to Th02. Dilute the solution with water till the thorium concentration is exactly 1 mg/ml. Working solutions are obtained by appropriate dilution of the standard solution with 0.1 M HNO3. 

Bitea et al. [2003BIT/MUL] discuss the stability of thorium colloids generated by cou-lometric titration of 10 to 10 M thorium solutions at pH 3 - 5 in 0.5 M NaCl. Using laser-induced breakdown detection (LIBD) and ultrafiltration the colloids formed above the solubility limit of Th(lV) hydroxide were found to be stable within the time period of investigation (up to more than 400 days). Dilution of colloid containing test solutions at constant pH leads to the degradation of colloids into soluble ionic species, whereas dilution with neutral 0.5 M NaCl results in increased over-saturation and colloid formation, as recognised by a pH shift to lower values. This observation was ascribed to the simplified reaction ... 

In addition, [2006ALT/NEC] contains a brief section on EXAFS measurements. The spectram of a thorium solution in 1.0 M Na2C03 / 0.1 M NaHCOs is consistent with those measured in [1997FEL/RAI] for thorium solutions at high carbonate or bicarbonate concentrations. The different EXAFS spectram of a saturated solution taken from the solubility study at / = 0.5 M (NaHC03-Na2C03-NaCl), Qot= 0.1 M, and... 

This Is Immaterial for colorimetric or fluorlmetrlc finishes, but, for determination of the uranlum-233 by alpha counting, the blsmuth-212 must first be allowed to decay. If, however, the uranlum-233 Is extracted as Its 8-hydroxyqulnollne complex, no alpha emitter accompanies It and concentrations of uranlum-233 ranging from 100 t g per ml down to 0,01 iig per ml In 0.7 H thorium solution have been determined In this way. 

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