Note 11 — Chapter XX · SULPHUR, SELENIUM, AND TELLURIUM

Here, however, it is very important to remark that both benzene and acetylene can exist at the ordinary temperature, whilst the sulphur molecule S2 only exists at high temperatures; and if this sulphur be allowed to cool, it passes first into S6 and then into a liquid state. Were it possible to have sulphur at the ordinary temperature in both the above modifications, then in all probability the sulphur in the state S2 would present totally different properties from those which it has in the form S6, just as the properties of gaseous acetylene are far from being similar to those of liquid benzene. Sulphur, in the form of S2, is probably a substance which boils at a much lower temperature than the variety with which we are now dealing. Paterno and Nasini (1888), following the method of depression or fall of the freezing-point in a benzene solution, found that the molecule of sulphur in solution contains S6.

One must here call attention to the fact that sulphur, with all its analogy to oxygen (which also shows itself in its faculty to give the modification S₂), is also able to give a series of compounds containing more atoms of sulphur than the analogous oxygen compounds do of oxygen. Thus, for instance, compounds of 5 atoms of sulphur with 1 atom of barium, BaS₅, are known, whereas with oxygen only BaO₂ is known. On every side one cannot but see in sulphur a faculty for the union of a greater number of atoms than with oxygen. With oxygen the form of ozone, O₃, is very unstable, the stable form is O₂; whilst with sulphur S₆ is the stable form, and S₂ is exceedingly unstable. Furthermore, it is remarkable that sulphur gives a higher degree of oxidation, H₂SO₄, corresponding, as it were, with its complex composition, if we suppose that in S₆ four atoms of sulphur are replaced by oxygen and one by two atoms of hydrogen. The formulæ of its compounds, K₂SO₄, K₂S₂O₃, K₂S₅, BaS₅, and many others, have no analogues among the compounds of oxygen. They all correspond with the form S₆ (one portion of the sulphur being replaced by oxygen and another by metals), which is not attained by oxygen. In this faculty of sulphur to hold many atoms of other substances the same forces appear which cause many atoms of sulphur to form one complex molecule.