Definify.com

Webster 1913 Edition

Vacuum

Vac′u-um

(văk′ū̍-ŭm)
,
Noun.
;
pl. E.
Vacuums
(văk′ū̍-ŭmz)
, L.
Vacua
(văk′ū̍-ȧ)
.
[L., fr.
vacuus
empty. See
Vacuous
.]
1.
(Physics)
A space entirely devoid of matter (called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means;
as, water boils at a reduced temperature in a
vacuum
.
2.
The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.;
as, a
vacuum
of 26 inches of mercury, or 13 pounds per square inch
.
Vacuum brake
,
a kind of continuous brake operated by exhausting the air from some appliance under each car, and so causing the pressure of the atmosphere to apply the brakes.
–
Vacuum pan
(Technol.)
,
a kind of large closed metallic retort used in sugar making for boiling down sirup. It is so connected with an exhausting apparatus that a partial vacuum is formed within. This allows the evaporation and concentration to take place at a lower atmospheric pressure and hence also at a lower temperature, which largely obviates the danger of burning the sugar, and shortens the process.
–
Vacuum pump
.
Same as
Pulsometer
, 1.
–
Vacuum tube
(Phys.)
,
(a)
a glass tube provided with platinum electrodes and exhausted, for the passage of the electrical discharge; a Geissler tube.
(a)
any tube used in electronic devices, containing a vacuum and used to control the flow of electrons in a circuit, as a vacuum diode, triode, tetrode, or pentode.
–
Vacuum valve
,
a safety valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere, in order to prevent collapse.
–
Torricellian vacuum
.
See under
Torricellian
.

Webster 1828 Edition

Vacuum

VAC'UUM

,
Noun.
[L.] Space empty or devoid of all matter or body. Whether there is such a thing as an absolute vacuum in nature, is a question which has been much controverted. The Peripatetics assert that nature abhors a vacuum.
Torricellian vacuum, the vacuum produced by filling a tube with mercury, and allowing it to descend till it is counterbalanced by the weight of the atmosphere, as in the barometer invented by Torricelli.

Similar Results