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 . 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.