3575.     VON STACKELBERG, M.  [Investigations on Carbides.  I.  Crystal Structure of Carbides MeC2.]  Ztschr. physik. Chem., vol. 9, 1930, B, pp. 437-475; Chem. Abs., vol. 25, 1931, p. 11.

        X-ray investigation by the powder method of a series of carbides of formula MeC₂ shows that they have a face-centered tetragonal lattice with 4 mol. in the unit cell and lattice constants as follows, recording a, c, and the density in order:  CaC₂, 5.48, 6.37, 2.21; SrC₂, 5.81, 6.68, 3.26; BaC₂, 6.22, 7.06, 3.90; LaC₂, 5.54, 6.55, 5.35; CeC₂, 5.48, 6.48, 5.56; PrC₂, 5.44, 6.38, 5.75; NdC₂, 5.41, 6.23, 6.08; ThC₂, 5.85, 5.28, 9.3; NaHC₂, 5.40, 8.17, 1.33; KHC₂, 6.05, 8.42, 1.37.  The C-C distance in the C₂ group is 1.4 Å. U., agreeing with band spectra data.  With the help of the polarizing microscope the tetragonal symmetry was confirmed for CaC₂, SrC₂, and BaC₂.  An electron configuration similar to that of the N₂ molecule is postulated for the C₂ and HC₂ groups.  The possible space-group classifications are discussed.  These carbides appear to show a new lattice type somewhat similar to that of pyrite.