This is a copper and glass essential oil separator, also called an essencier. It is used to separate the essential oil from the hydrosol during distillation and is a good alternative to a separatory funnel.
It is especially useful for plants or still sizes that don’t produce much essential oil per distillation. The small amount of essential oil from multiple distillations will accumulate in the glass tube until there is a volume that is easier to collect with a dropper or pipette.
The distillate (mixture of hydrosol and essential oil) is directed from the condenser outlet to the glass tube. The essential oil accumulates in the glass tube part of the separator and the hydrosol flows out of the copper spout.
Instructions with photos included. Size is 11.5 inches tall by 4.5 inches wide at the base.