heating cap
Выражение встречается в следующем контексте:
Production of essential oils:
Steam distillation
The distillation apparatus consists of heating cap, a 1 L extraction flask, a 3 ml graduated receiver (Dean and Stark) and condenser (jacketed coil). The weighted plant material and 0.7 L H2O were used and the distillation was carried out for 4 h after reaching the boiling point.

Заранее спасибо