Mercury is oldest way to cath gold, and it still works now. In past days, miner burn the calomelene（calomelene is the mixture of gold and mercury); the mercury evaporates and gold remains. It waste money on mercury, and also bad for worker health and environment.
The following is a mercury recoverer. The working process is :
A. Unscrew the screw & nut, put calomelene inside, screw the screw & nut.
B. Put recoverer on fire. When it heat up, the calomelene becomes mercury steam and gold. Adjust the pressure by switch 3, so steam won’t eject out.
C. Arrage water, water flow in from 1 and flow out from 2. The mercury steam will be cool down and become mercury liquid.