FRACTIONAL DISTILLATION • DICCIONARIO INGLES.COM • Definition of Fractional distillation

... oil, where the proportion of aldehydes, though of great importance, is relatively very small, it is necessary to first concentrate the aldehydes before determining them. For this purpose, 100 c.c. of the oil is placed in a Ladenburg fractional distillation flask, and 90 c.c. distilled off under a pressure of not more than 40 mm., and the residue steam distilled. The oil so obtained is separated from the condensed water, measured, dried, and 5 c.c. assayed for aldehydes either by the process already described, ...

— The Handbook of Soap Manufacture • W. H. Simmons