Some concentration of the carcinogenic material in a Venezuelan spindle grade oil has been affected by simultaneous molecular distillation, and further concentration has also been accomplished by subjecting one of the more carcinogenic of these distillates to chromatographic adsorption. Animal experiments revealed that this distillate was about twice as carcinogenic as the oil from which it was derived. Two small fractions obtained from this distillate by chromatographic adsorption were painted on the skin of a few mice and both appeared to be appreciably more carcinogenic than the distillate from which they were derived. Further experiments with one of these fractions and the distillate, not yet completed, indicate that this fraction is at least five times as strong as the distillate from which it was derived. Thus by a combination of molecular distillation and chromatographic adsorption processes we have obtained a fraction about ten times as strong as the original oil. During the chromatographic adsorption process large quantities of colourless, low index, inert or almost inert material of relatively low viscosity have been separated from the highly coloured active remainder. It would appear that the most active material is highly viscous at room temperature, but its activity may be due to the presence in it of crystalline solids.

In conclusion we wish to express our thanks to our steward, Mr L. Norburn, for his valuable assistance in the practical work.