THE silicones, those derivatives of silicm analogous to the ketones in structure, have not yet been very carefully studied, and, in fact, only a few compounds of this type have hitherto been prepared. Thd simplest known representative, diethylsilicone, Et,SiO, WRS obtained long ago by Friedel (Ann. chim. phys., 1866, [iv], 9, 5) ; diphenplsilicone, Pb,SiO, has been described by Dilthey (Ber., 1 905, 38, 4132), and phenylethylsilicone, PhEtSiO, was prepared by one of us a short time ago (Trans.,

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... 1907, 91, 218). In the course of some recent experiments (Kipping, Trans., 1907, 91, '720), it was found that benzylethylsilicon dichloride could be easily obtained in a pure state; as this compound is decomposed by water, giving benzylethylsilicone, BzEtSiO, we have studied the behaviour of this silicone in order t o ascertain whether i t shows any similarity to the corresponding ketone. We may say at once tE&t it does not ; benzyl ethyl ketone boils a t 226' under atmospheric pressure ; benzylethylsilicone at 305-315' under a pressure of 22 mm. This very high boiling point of the silicone doubtless indicates molecular complexity, and the reEults of ebullioscopic experiments bear out this indication, the values obtained in acetic acid and in acetone pointing to the termolecular formula (BzEtSiO),. In this respect, benzylethylsilicone resembles diphenylsilicone (Dilthey, Zoc. c i t . ) ; dibenzylsilicone, which is described in this paper (p. 452), is also represented by the molecular formula (Bz,SiO)" and, judging from its high boiling point (above 360°), diethylsilicone has an analogous molecular complexity. It would seem, therefore, that silicones, as a class, differ from the ketones in readily forming comparatively stable molecular aggregates, but whether the latter are to be regarded as composed of loosely associated, or of chemically united, molecules we have as yet no satisfactory evidence before us. This association, polymerisation, or union of the simple silicone molecules is probably one of the reasons, but not the only one, why in other respects also the silicones show no relationship with the ketones ; thus we find that benyzlethylsilicone does not undergo change when it is treated with certain reagents which reduce ketones; we also find that the silicone does not react with hydroxylamine or with phenylhydrazine when treated with these reagents in the ordinary