Vol. 72
4504
Magnetic Susceptibilities of Urania-Thoria Solid Solutions BY W. TRZEBIATOWSKI~ AND P. m7. SELWOOD~ The magnetic moment of the U*4 ion has been determined by several authors from magnetic susceptibilities of uranium compounds,a-Q but the theoretical calculation of the moment is difficult, because indeterminate factors influence each value. For elimination of some of these factors it seems to be advantageous to determine the magnetic uioment of U+4in a state of dilution such as may exist in solid solutions of uranium dioxide with diamagnetic thorium dioxide. These compounds, being isomorphous, may be expected to form a continuous range of solid solutions with the fluorite structure.
Experimental
lo+, and with solid ferrous ammonium sulfate for which the susceptibility a t 25" was taken as 31.6 X 10-B.13 Both experimental arrangements provided a hydrogen atmosphere around thc suspended sample tubes. N o systematic dependence of the susceptibility a t the three different field strengths was observed. This assured that the samples did riot contain ferromagnetic impurities in appreciable amount. The average value of the susceptibilities measured as 4910 and 5700 oersteds was employed. The differences between susceptibilities obtained a t thesr two field Etretigths in no case evceeded 0.08 X IO-'
Results The values of the mass susceptibilities are presented in Table 1. From these data, the molar susceptibility of ITwas calculated according to the formulas
Preparation of Solid Solutions.-Uranium
acetate (Anal. Reag. Mallinckrodt Chem. Works) and thorium nitrate (Lindsay Light and Chem. Co.), the latter stated to contain less than 0.003% rare earths, were used. tkaniutn dioxide was obtained by precipitating a dilute solution of the acetate with ammonia water and reducing the diammonium uranate a t llOOo, using electrolytic hydrogen which 'had been passed through palladiumasbestos, coned. sulfuric acid and phosphorus pentoxide. Thorium dioxide was obtained by ignition of the thorium nitrate a t 1100'. For preparation of solid solutions, mixtures of about 50 g. af uranium acetate and thorium uitrate, in proportions related to the desired oxide content, were dissolved in 3 1. of water containing 20 ml. of 20% nitric acid pius 3% ammonium nitratc:. Coprecipitation of an intimate mixture of ammonium uranate and thorium hydroxide was obtained with 5y0 ammonia water in the presence of methyl red,'" while the solution was vigorously stirred. It was confirmed that precipitation was quantitative The precipi wds washed with 2% ammonium nitrate solution, dr and, after preliminary ignition, reduced for three hours a7 1200' in hydrogen, the solid solution being formed simultaneously. The samples nd the structure was confirmed by X-ray powder S. Measurements.-A Gouy balance was used a t engths of 3750, 4910 and 5700 oersteds. Two different arrangements were used for temperature control. The first provided successive measurements at eight different temperatures from 25 to - 128',11 and the second permitted measurements at liquid air temperature and at the temperature of a solid carbon dioxideacetone freezing mixture.'* Sample tubes, in two sizes, contained 3.6 and 17 g . of substance, respectively, and were calibrated with standard 20yonickel chloride solution for which the susct-ptihility a t 23" was taken R C 6 I5 (I) UNESCO-Amrrirdn Chemical Suclety Fclloa (2) Inquiries i'onr-t n i i t t : thiq piiper .hnuld he ?Adre Selwood. (3) Sucksmith Pht! t l n , 14, ILL5 ( 1 Y W (4) Lawrence, 1 vi%Inr R \ A I , 56, 770 (19.74) ( 5 1 Haraldsen and Ilahkrn .\ntuvwzsr 28, 127 (1940) (61 Bommer, Z i8rrorg ollqepn Chcnz , 247, 249 (1941) 171 Howlend an
