Abstract
THE relations between the allotropic forms of Jcarbon constitute one of the most baffling problems in chemistry. The hardness and incompressibility of the diamond point to its structure as being an exceedingly stable one, and the examination by X-rays proves it to have the tetrahedral lattice which accords with the known chemical properties of the carbon atom. On the other hand, graphite has its atoms arranged in sheets made up of hexagons, the carbon atoms in that plane being actually closer than in the diamond (1.42 instead of 1.53 Angstrom units), but the sheets are widely separated, their distance being 3.41 A., so that the structure is a loose one, corresponding with the easy cleavage. Graphite is readily produced from diamond at high temperatures, but the converse change has presented the greatest difficulties, graphite having shown itself under all conditions to be the more stable modification. It has been supposed that the atoms of carbon in the two substances differ in their electronic structure, the atom in diamond having four 21 orbits, and that in graphite only three 21 orbits and one of the 22 form, an arrangement which is consistent with the two space lattices and also with the great difference in electrical conductivity between the two modifications. It is doubtful whether specimens of graphite have ever been obtained quite free from other elements, and Prof. H. E. Armstrong has maintained that it always contains hydrogen, which is the cause of its open structure.
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D., C. The Problem of Artificial Production of Diamonds. Nature 121, 799–800 (1928). https://doi.org/10.1038/121799a0
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DOI: https://doi.org/10.1038/121799a0
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