An examination of the action of certain compound halogens towards some of the olefines (the results of which I hope shortly to lay before this Society), has led me to consider incidentally the preparation of some of the compound halogens in the pure state.

Of compound halogens, while the constitution of none is more invariable and definite than that of the bisulphide of chlorine, the bisulphide of iodine can scarcely be said to have been prepared, despite the so strong analogy between chlorine and iodine.