A direct titrimetric method for the determination of trivalent uranium in uranium trifluoride and mixtures of fused fluoride salts was developed. The method is based on the stoichiometric oxidation of trivalent uranium to the tetravalent oxidation state with an acidic solution of methylene blue. The sample containing trivalent uranium is dissolved at room temperature in an excess of standard methylene blue solution in a carbon dioxide atmosphere; the excess oxidant is variation of the method is 1.5 per cent for 5 mg quantities of trivalent uranium. The method was applied to various mixtures of fluoride salts containing both trivalent and tetravalent uranium.

Mercury to be used in polarography as a dropping mercury electrode must be of the highest purity. The author has found that much of the commercial "triple-distilled" mercury as well as that which is repurified on site is not sufficiently pure and because of this, a study of mercury purification techniques was made and a very satisfactory procedure was tested thoroughly. This procedure is described in detail in this report.