The heats of formation of UAl2, UAl3, and UAl4

Preparations of the intermetallic compounds UAl₂, UAl₃ and UAl₄ were obtained by high-temperature interdiffusion of aluminum and dispersed uranium, prepared by decomposing its hydride then grinding the product and heating the powder obtained. Debye x-radiographic investigation showed that the preparations obtained consisted of one phase and the parameters of their structures were close to those published earlier. The amount of hydrogen evolved during separate solution of the preparations and the starting components in a specially selected solvent (mixture of HCl, H₃PO₄, Na₂SiF₆, H₂PtCl₅ and CuSO₄· 5H₂O) Indicated that the preparations had the compositions; UAl_1.997, UAl_2.994 and UAl_3.997.The differences in the heats of solution of these preparations and appropriate mixtures of their components gave die heats of formation (–H°₂₉₃)UAl₂, UAl₃ and UAl₄, which were 22.3±2.4, 25.2±2.2 and 31.2±3.1 kcal/mole, respectively.The authors would like to thank N. T. Chebotarev and P. N. Petrov for the x-radiographic analyses of the preparations, T. S. Men'shikova for the metallographic investigation and L. M. Kopytin for his valuable advice and interest in the work.