Abstract Some years ago I ascertained that chloride of iodine combines directly with the olefines and the non-saturated haloid ethers in the same manner as free chlorine or bromine. I have since ascertained that bromide of iodine also enters into direct combination with these bodies. In the following experiments I have invariably used a solution of bromide of iodine in water, which was prepared by adding rather more than a molecule of iodine in fine powder to a molecule of bromine previously mixed with about six times its weight of water. The bromine was repeatedly agitated during the addition of the iodine, and kept cold by being surrounded by water. An almost black liquid was thus obtained, which was separated from the excess of iodine.