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.. The above theory describes many properties of liq_uid sulphur below and above the viscosity maximum very well by assuming that, at the melting point, the liq_uid constants of free s units, which towards 160°C polymerize 8 to a number-average degree of over 105 Sn units. At still higher temperatures •0 a steady depolymerization is asramed. Many properties indicate, however, that liq_uid sulphur is in reality :::till a much more complicated system than described above. The meltine: process is a good example of such behaviour:. It is long.known that sulphur has a "natural" and an "ideal" melting point. It. seems that a new component forms in the liq_uid phase, which, as a solute, causes a self-solution of sulphur in cyclo-s8. The search. for this component has after almost one hundred years of intermittent work recently been taken up again and molecular weight determinations of this "S7T" and the cryoscopic data indicate that it might consist of catena-s8• This component S7T can be separated from cyclo-:_Ss ·by dissolving it in cs at dry ice temperature, 2 wher~orthorhombic sulphur is not very soluble (37). The assumption of up . to 4% catena-s8 in liq_uid sulphur is however complicated by the ESR evidence that only irrelevant amounts of free radicals exist below 160°C. However, short chains of up to eight atoms might stabilize the free electron.through resonance and might, therefore, give a very broad ESR signal (38)•. Since preparation and isolation of such small molecules is experimentally feasible _(gJ)" it seems not timely to speculate about their properties. The melting phenomenon might be caused by another component bes.ides cycloocta. S: The .• • gas phase studies indicate the presence of more than 10% of s6 and s7 each· in the saturated vapour at 120° (22), and it seems reasonable to assume that both occur also in the liq_uid. The mass spectroscopic data indicate that at the boiling point s7 '! r• .'·· .... (- 4o% of vapour) and s6 (- 30%) are more abundant than s8 (20%) in the -11- .· ~ ....PDF Image | ELEMENTAL SULPHUR
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