torr /tôr/ [Evangelista Torricelli, Italian physicist, 1608–1647] , a unit of pressure equal to 1333.22 dynes/cm2, or 1.33322 millibars. One torr is the pressure required to support a column of mercury 1 mm high when the mercury is of standard density and subjected to standard acceleration. These standard conditions are 0° C and 45° latitude, where the acceleration of gravity is 980.6 cm/sec2. In reading a mercury barometer at other temperatures and latitudes, corrections commonly exceeding 2 torr may be required to compensate for the thermal expansion of the measuring scale used.
