Purify it by fractionation under reduced pressure in vacuo, and if it is almost pure it can be fractionated at atmospheric pressure, preferably in an inert atmosphere. It forms two semicarbazones one of which is more soluble in *C6H6, and both can be recrystallised from EtOH; the more soluble has m 149o(151o), and the less soluble has m 172-175o(191o). The 4-nitrophenylhydrazone has m 166-167o and the 2,4-dinitrophenylhydrazone has m 114-115o. [Pfau & Plattner Helv Chim Acta 17 129, 142 1934, Adler & Vogt Justus Liebigs Ann Chem 564 109 1949.]
