“…In order to get homogeneous mixtures without decomposition, mixtures, 2 g, were previously melted several times at a temperature a few degrees over the melting point. Trigonal [3][4][5][6][7][8][9] a (296 to 427) K [10][11][12] Trigonal [10,11] b (440 to 509) K [1,3,6,10] Cubic (CsCl) [3][4][5]8] b (439 to 683) K [1,[10][11][12] Cubic (CsCl) [1,12] c (509 to 560) K [8,10,13,14] Trigonal [8,9,15]; Tetragonal [3]; Cubic [4,7,14] d (560 to 584) K [8,9,16] Cubic (NaCl) [8] k (564 to 584) K [17][18][19][20] ?…”