It has been found that a joint action of hydrogen bromide and oxygen accelerates the addition of bromine to cinnamic acid in carbon tetrachloride solution in the dark, whereas the reaction is retarded by either of them. The catalyzed reaction is prevented by catechol, and hydrogen chloride cannot be substituted for hydrogen bromide without the dis？ppearance of the accelerating effect. On the basis of these observations the nature of the alleged catalysis of the addition of bromine by hydrogen bromide has been elucidated. The elimination of the induction period, which is certainly attributable to the inhibitory action of oxygen, is not due to the removal of the latter. The explanation offered is that hydrogen bromide and an ethenoid compound in co-operation with the very oxygen starts a rapid chain reaction involving bromine atoms and free radicals. Also for the uncatalyzed addition of bromine to cinnamic acid in carbon tetrachloride a possibility of a mechanism involving chains has been suggested.
Dialkyltin sulphide has been prepared by treating dialkyltin dihalide with KSH in absolute alcohol, saturated with hydrogen sulphide. The six-membered hetero-cyclic structure (Remark: Graphics omitted.) and the term tri-thio-anhydro-tris-dialkylstanne-dithiol are suggested for the compound from the results of the molecular weight determination.