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Published June 1, 1929 | public
Journal Article Open

The Valence of Sulfur in Dithionates

Abstract

It has been shown by Lindh [1] and others [2] that the shift in the K absorption edges for various compounds of sulfur, chlorine, phosphorous, iron, and some other substances, depends chiefly on the valence of the element in a given compound. With increasing valence in a given element the wave-length of the edge shifts to smaller values. Stelling [3] has explained the effect of valence as being due to the screening effect of electrons in external parts of atoms. To be sure, other factors influence the position of the edges, such as other elements occurring in the compounds, and lattice structure, but these factors produce in general only minor fluctuations around a mean value, whereas the mean values for the several valences show rather wide divergences. For example, the wave-lengths of the principal K edge of a large number of 4- and 6-valent inorganic sulfur compounds practically all lie within half an X-unit of the means of their respective groups, whereas the means themselves are separated by 8 X. U. A similar state of affairs is observed in the 2-valent compounds. The edges do not lie quite so close to the mean, but the mean is 13 X. U. from that of the 4-valent compounds. All the substances thus far investigated bear out the general statements above. In view of the rather large body of facts now before us, it seems legitimate to try to use x-ray absorption data to obtain information on the valence state of an element in a compound. The substance used in the present investigation was potassium dithionate, the object being to determine the state of the two sulfur atoms in K2S2O6. Lindh [4] has already shown that for Na2S2O3 and some other thiosulfates there is not just a simple absorption edge, but two edges, corresponding in position to the valence states SII and probably Siv, which states are generally assumed by chemists for the two sulfur atoms in the thiosulfates. Now if valence is calculated in the usual way, then on the assumption that the sulfur atoms of the dithionates are in the same state we get for them a valence of V, and we would expect to find the K absorption edge corresponding to a single state, rather than the two edges shown by the thiosulfates.

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Copyright © 1929 by the National Academy of Sciences Communicated April 19, 1929

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