ALTHOUGH the numerous researches of Harries, Staudinger, Pummerer and their collaborators have in recent years enriched our knowledge of the chemistry of rubber, the number of derivatives of rubber prepared up to the present is very few, and the number of atomic groups or radicals which it has been possible to introduce in the polyisoprene chain is still smaller. The reason for this is that rubber itself and its halides and hydrohalides have only a limited reactivity because of their colloidal nature and their slight solubility. Among those already known, the most interesting derivative is that obtained many years ago by C. O. Weber by the action of phenol on rubber dibromide. This was considered by Weber to be a phenolic ether, whereas Fisher, Gray and McColm have recently shown that it is a condensation product of hydrorubber and has free phenol groups.