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Crystal Structure of Rhombohedral Sulphur

1958; Nature Portfolio; Volume: 182; Issue: 4634 Linguagem: Inglês

10.1038/182518a0

1476-4687

Jerry Donohue, A. Caron, Elihu Goldish,

Nitrogen and Sulfur Effects on Brassica

The allotropic form of sulphur first discovered by Engel1 has been variously termed Engel's sulphur, Sɛ, Sρ, Sϕ, trigonal sulphur, and rhombohedral sulphur. The molecule was shown to be hexameric by Aten2. Friedel3 found the crystals were hexagonal prisms terminated by a flat rhombohedron. Although these crystals are largely converted to a mixture of plastic and orthorhombic sulphur an hour or so after they have been exposed to air or X-rays, Frondel and Whitfield4 were able to determine the hexagonal lattice constants, show that the symmetry axis was three-fold, and demonstrate the absence of vertical planes of symmetry; the lattice constants, combined with the observed density1, give 18 sulphur atoms per unit cell. The quality of their photographs was such that they were unable to determine whether the lattice mode was hexagonal or rhombohedral. Their X-ray study, however, combined with the morphological observations, established the point group as C 3i–&3bar; and Donnay5 later pointed out that on purely morphological grounds the lattice is rhombohedral and that the space group is thus probably C 3i 2–R&3bar; (No. 148).