The retort, also known as a mercury retort or mercury amalgam retort, is the most commonly used mercury amalgam retort equipment in the gold extraction process of small and medium-sized mines.

Because the gasification temperature of mercury is lower than the melting point and boiling point of gold, the mercury and gold in the mercury paste are separated by distillation, and the solid mercury paste produced by the gold concentrator can be distilled regularly. During operation, the solid amalgam is placed in a sealed cast steel tank, the roof of which is connected to an iron pipe containing a condensing pipe. The can is heated in a heating furnace such as coke, gas or electric furnace, and when the temperature slowly rises to 356 degrees, the mercury in the mercury paste is vaporized and escapes along the iron pipe, and is recovered in a spherical drop below the container of water after condensation. In order to fully separate the mercury in the mercury paste, many gold processing plants will control the temperature of mercury evaporation at 400-450 degrees, and the temperature will rise to 750-800 degrees in the later stage of mercury evaporation, and remain for 30 minutes. The mercury evaporation time is 5-6 hours, and the recovery rate of mercury in the mercury evaporation operation is usually greater than 99%. Small and medium-sized mines use multi-purpose distillation tank for mercury distillation, and large mines use distillation furnace.