vacuum-gage

Century Dictionary and Cyclopedia

1. n. A form of pressure-gage for indicating the internal pressure or the amount of vacuum in a steam-condenser, a boiler in which the steam has condensed, the receiver of an airpump, etc. A common form consists of an inverted graduated siphon of glass, open at one end, and connected at the other with the condenser or vessel to be tested, and containing a quantity of mercury. When not in use, the mercury rises equally in both legs of the siphon; on connecting the instrument with a vacuum, the mercury rises in the leg next the condenser or other vessel, and sinks in the other leg, the difference between them indicating the amount of the vacuum. This form is also called barometer-gage. E. H. Knight.