Some experiments on vacuum distillation

Crude petroleum and various petroleum derivatives have been distilled under conditions practically equivalent to evaporation into a perfect vacuum. Derivatives of very high molecular weight can be fractionated in this way without detectable decomposition. Decomposition (“cracking”) sets in quite suddenly, at temperatures varying from 307° to 340°C. for the oils tried. Greases and oils can be produced having exceedingly low vapour pressures at room temperature: the former permit the free use of ground joints in high- vacuum systems (10-6 mm.): the latter can replace mercury in condensation pumps, and the liquid-air trap is then unnecessary in many cases,e. g. , the exhaustion of thermionic valves.