Note 37 — Chapter XVIII · SILICON AND THE OTHER ELEMENTS OF THE FOURTH GROUP

Many volatile compounds of tin are known, whose molecular weights can therefore be established from their vapour densities. Among these may be mentioned stannic chloride, SnCl4, and stannic ethide, Sn(C2H5)4 (the latter boils at about 150°). But V. Meyer found the vapour density of stannous chloride, SnCl2, to be variable between its boiling point (606°) and 1100°, owing, it would seem, to the fact that the molecule then varies from Sn2Cl4 to SnCl2, but the vapour density proved to be less than that indicated by the first and greater than that shown by the second formula, although it approaches to the latter as the temperature rises—that is, it presents a similar phenomenon to that observed in the passage of N2O4 into NO2.