A REINVESTIGATION OF CRYSTAL STRUCTURE OF AMMONIUM PERSULFATE, (NH4)2S208

Ammonium persulfate, (NH4)2S2O8, is monoelinic with space group P2i/c, and isotypic with the corresponding caesium compound. The unit-cell parameters are: a = 7.830, c = 8.008, c = 9.505 Å, β = 139.93°. Atomic coordinates and thermal vibration parameters have been refined by means of the full-matrix least-squares method, and on the basis of new three-dimensional x-ray diffraction data obtained with a manual counter diffractometer, to a final value of the discrepancy index R of 0.086. The S2082~ group consists of two S042~ groups linked together by a covalent bond between two oxygen atoms. The S2082_ groups are in the crystal structure arranged in layers parallel to (100), these layers being held together by the interspaced layers of ammonium groups. Each ammonium group has twelve nearest oxygen-atom neighbours at distances ranging from 2.90 to 3.62 Å. The S-O bond in the[formula omitted]bridge is 1.644 ± 0.005 A, and the mean value of the other S-O bonds is 1.427 ± 0.003 A. n bonding appears to be responsible for the observed variations of the S-O bond lengths. © 1969, Walter de Gruyter. All rights reserved.