The polymerization of sulfur

Abstract

Abstract A previous analysis of the polymerization of liquid sulfur has been revised to take account of specific heat data now available and some new experimental evidence presented here. It is confirmed that liquid sulfur is essentially an equilibrium mixture of S 8 rings and long free radical chains. The heat of polymerization (S 8 → inifinite chain) is estimated as 3180 cal./mole of S 8 at 432°K., where polymerization sets in rather abruptly; the corresponding entropy of polymerization is +7.4 cal. mole −1 deg. −1 . There is evidence for the presence of rings of more than 8 atoms; the concentration of these reaches a maximum of ca . 1% in the neighborhood of the critical polymerization temperature (432°K.). Magnetic susceptibility measurements place an upper limit of 2 × 10 −2 moles l. −1 on the free radical concentration. From this and other lines of evidence it is concluded that the heat of scission of sulfur chains does not exceed 35 kcal., and an explanation is put forward.