β-phellandrene does not form a tetrabromide, and indeed we have found no reference in the literature to the formation of such a compound by a conjugated terpene apart from a recent record of a liquid tetrabromide derived from α-terpinene1. During examination of the terpene fractions of the oil from Eucalyptus cneorifolia, we repeatedly isolated a crystalline tetrabromide which had m.p. 110–112° and was