PROMOTING ACCESS TO AFRICAN RESEARCH

Bulletin of the Chemical Society of Ethiopia

Log in or Register to get access to full text downloads.

Remember me or Register



Thermal stability of Vernonia galamensis seed oil

Benny M. Wamalwa, Esther N. Njuguna, Paul M. Shiundu, Geoffrey N Kamau

Abstract


. The physicochemical changes of refined vernonia oil?RVO (which naturally contains epoxidized triglycerides) upon heating was evaluated and is reported in this manuscript. A boiling point range of 183 °C to 190 °C (at 760 mm Hg) for the vernonia oil was obtained using the Siwolobboff's method. The oil changed its physical appearance and consistency in the course of the heating. A homogenous free?flowing beige?sand shade refined vernonia oil at room temperature (25 °C) was transformed irreversibly to an intense?brown shade, becoming increasingly more viscous with increase in temperature, and ceasing to flow momentarily at 188 °C. On cooling to room temperature, the oil solidified into a brown rubber?like elastic material. The oil also exhibited a reduction in its oxirane content from 1.39±0.004 equivalent HBr kg?l at 25 °C to 0.542±0.002 equivalent HBr kg?l at 70 °C. This signifies a 61% drop in oxirane content for the 45 °C temperature rise. These findings point towards a thermally driven polymerization and/or decomposition of the refined vernonia oil (RVO).
(Received May 20, 2000, revised December 13, 2000)

Bull. Chem. Soc. Ethiop. 2000, 14(2), 161-168



AJOL African Journals Online