Examination of the hexamethylenetetramine procedure for separation of thorium from rare earths and for determination of thorium.
An examination has been made of the efficiency of the gravimetric reagent hexamethylenetetramine in the separation of thorium from rare earths and in the determination of thorium. Losses to the filtrate, beaker and filter paper are evaluated as well as the extent of rare earth and other contamination of the thorium hydroxide precipitate. When hydroxylamine is used as the reducing agent to keep cerium in the tervalent state, excellent separations are obtained. The efficacy of the reagent is offset by the loss of small amounts of thorium to the precipitation vessel, the scavenging properties of the precipitate for silica and the difficulty in evaluating a true reagent blank.
Direct determination of small quantities of rare earth and yttrium oxides in thoria by emission spectroscopy.
Methods are proposed for the determination of submicrogram quantities of rare earth and yttrium oxides in thorium oxide by emission spectroscopy, without previous separation or concentration of these oxides in the sample. It is possible to volatilise these refractory materials from the thoria using silver chloride as the carrier. The carrier distillation technique in conjunction with relatively high dispersion spectroscopy (0.8-1.1 A/mm) makes possible analyses at levels which were previously only feasible by preconcentration methods (e.g., La(2)O(3) and Y(2)O(3), 5 ppm; Nd(2)O(3) and Sm(2)O(3) 10 ppm; CeO(2) and Pr(6)O(11), 20 ppm in a 10-mg sample of ThO(2)).
An Electron Diffraction Camera for the Study of High Temperature Surface Reactions
An electron diffraction camera is described for the study of physical and chemical reactions occurring on the surfaces of metals and alloys in situ at elevated temperatures. The specimen is mounted in a metal block and shielded from the surrounding cold surfaces by a series of metal shields. The metal block contains an internal electrical heater which allows the temperature of the specimen to be accurately controlled at temperatures of 800°C. Gas purification chains are included for the preparation of pure oxygen, hydrogen, etc. Several typical electron diffraction reflection studies of the oxidation of iron and stainless steel are included.