The steam rising from the latter is passed into a similar pan, in which it circulates round another set of pipes, but as it could not bring the liquid in the latter to boil under ordinary conditions, the second pan is connected with a vacuum-pump so that the boiling-point of the liquid in this pan is lowered.
Fleuss consists of a vacuum pump capable of reducing the air pressure to a fraction of a millimetre, the suction pipe of which is connected first with a vessel containing sulphuric acid, and second with the vessel containing the water to be frozen.
For a cheaper alternative, many people use a home built vacuum pump made from one, or preferably two small refrigeration compressors.
Von Guericke had earlier prepared a large hollow sphere from which he had removed the air using a vacuum pump of his invention.
These uncharged particles will simply get lost in the machine - eventually, they get removed by the vacuum pump.
