Abraham Gesner produced coal oil by destructive distillation. The coal was heated in a closed retort until it gave off gases which were then distilled in a condenser. Gesner's method was adopted by petroleum refiners whose liquid raw material was distilled fractionally, that is, by condensing the gases progressively as the temperature of the oil was raised.
In the early days the process of distilling crude oil was a simple one. The oil was heated in a large cast iron retort (A) with a capacity of fifteen to twenty barrels. From this retort a solitary gooseneck (B) led to the condenser. After distillation the resulting fluid was "washed" with acid and water after which caustic soda was used to neutralize the acid (C). The refined oil could then be barrelled directly. The finished product was described as "a fine amber coloured oil that would make any chimney the same colour in about twenty minutes".
