Syntheses of neptunium trichloride and measurements of its melting temperature

Abstract Neptunium trichloride (NpCl 3 ) of high purity was synthesized by the solid state reaction of neptunium nitride with cadmium chloride. Lattice parameters of hexagonal NpCl 3 were determined from the powder X-ray diffraction pattern to be a = 0.7428 ± 0.0001 nm and c = 0.4262 ± 0.0003 nm, which fairly agree with the reported values. The melting temperature of NpCl 3 was measured on a sample of about 1 mg, hermetically encapsulated in a gold crucible with a differential thermal analyzer. The value determined was 1070 ± 3 K which is close to the recommended value (1075 ± 30 K) derived from the mean value of the melting temperature of UCl 3 and of PuCl 3 .