The mercury barometer Torricelli filled a tube with mercury and inverted it into an open container of mercury. Air pressure Po acting on the mercury in the dish can support a column of mercury 76 cm in height.
Standard atmospheric pressure The pressure that will support a column of mercury of 760.0 mm heigh is known as standard atmospheric pressure or 1 atmosphere (1 atm). 1 atm = 76 cmHg = 1.013 x 10 5 Pa = 10 3 millibar (mb)
Pressure from the air As the air is removed from the inside the external pressure crashes the can.