Torr

The torr (symbol: Torr) is a non-SI unit of pressure defined as ⁄760 of a standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimeter of mercury, i.e. a pressure of 1 Torr is approximately equal to 1 mmHg. Note that the symbol is spelled exactly the same as the unit, but the symbol is capitalized, as is customary in metric units derived from names. It was named after Evangelista Torricelli, an Italian physicist a... more

The torr (symbol: Torr) is a non-SI unit of pressure defined as ⁄760 of a standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimeter of mercury, i.e. a pressure of 1 Torr is approximately equal to 1 mmHg. Note that the symbol is spelled exactly the same as the unit, but the symbol is capitalized, as is customary in metric units derived from names. It was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644. Torricelli attracted considerable attention when he demonstrated the first mercury barometer to the general public. He is credited with giving the first modern explanation of atmospheric pressure. Scientists at the time were familiar with small fluctuations in height that occurred in barometers. When these fluctuations were explained as a manifestation of changes in atmospheric pressure, the science of meteorology was born. Over time, 760 millimeters of mercury ... less