The addition reactions of conjugated systems have been for some time the subject of an investigation in this Laboratory.1 In our earlier work we were mainly concerned with the addition reactions of -substituted conjugated compounds, RCH=CHCH=CH2, but in order to ascertain the effect of conjugation, free from the influence of substituent groups, we undertook an investigation of the addition reactions of butadiene, CH2= CHCH=CH2. The present paper contains the results of a study of the 4 Brooks, "Chemistry of Non-Benzenoid Hydrocarbons," The Chemical Catalog Co., Inc., New York, 1922, gives a rather complete review of the various methods that have been used for the preparation of butadiene.5 Perkin, J. Soc. Chem. Ind., 31, 616 (1912).