THE MOLECULAR COMPOSITION OF SOLIDIFIED P HOSPHORUS-SULFUR MELTS AND THE CRYSTAL-STRUCTURE OF BETA-P4S6

Phosphorus sulfur melts were annealed for one week at 673 K and then q uenched in ice water. The solids were dissolved in CS2 and the concent rations of phosphorus sulfides were determined by P-31 NMR spectroscop y. Samples containing between 44 and 70 mol% sulfur dissolved complete ly in CS2. Between 0 and 42 mol% remains an insoluble residue of red p hosphorus. Above 72 mol% it consisted of sulfur chains linked by phosp horus atoms. The solutions contained mainly the congruently melting co mpounds P4S3, P4S7, and P4S10 having maximum concentrations at their s toichiometric compositions. Other compounds P4Sn (n = 4-9) which decom pose on heating, according to the phase diagram, were also found in su rprisingly high concentrations. One of these was beta-P4S6 which cryst allizes in the monoclinic space group P2(1)/c with the lattice paramet ers a = 702.4(2), b = 1205.6(2), c = 1148.9(6) pm and beta = 103.4(2)d egrees. Reaction of white phosphorus with sulfur was also investigated . In contrast to the results of previous authors, who described the sy stem P-4-S-g below 373 K as eutectic, we found that the elements react ed below this temperature.