IN a series of investigations on the chemistry of resin acids, Ruzicka and his collaborators (Helv. Chim. Actn, 1922, 5, 585; 1923, 6, 677, 1082; 1924, 7, 470: 875), using the Vesterberg- Diels dehydrogenation technique (Bey., 2903, 36, 4200; Annalen, 1927, 459, l), isolated