On the polar habit of crystals of potassium tetrathionate, K2S4O6

Abstract

AbstractThe F forms, as defined by the Periodic Bond Chain Theory, of K2S4O6with space groupCchave been derived from the crystal structure. When each F form is characterized by the indices {nh,nk,nl} of its slice thicknessdnh, nk, nland when polarity is disregarded, the F forms are in decreasing order ofdnh, nk, nl: {200}, {110}, {[unk]11}, {111}, {400}, {310}, {[unk]11}, {002}, {[unk]02}, {311}, {202}, {[unk]02}, {[unk]12}, {312} and {402}. The description as given by Groth (Chemische Krystallographie, Vol. II, p. 717) contains several errors. A new description is given. The observed forms are all F forms. To explain the polar habit the hypothesis is made that the dehydration of the cations determines the growth rate of a face. This hypothesis leads to the prediction that {[unk]02} should be present at the positive end of thecaxis and {[unk]} at the negative end. This agrees with the observations.