Barometers

Torricelli made the experience showing how air pressure can counterbalance the pressure of liquid column. He took a glass tube with a length of about 1 meter zasklepił at one end and filled with mercury. Then zatkał tube with your finger, and turned away and put in a small open end of the vessel containing mercury. When he took a finger, part of Mercury przepłynęła tube to the dish and the liquid column over the vacuum created. However, a certain part of the mercury remained in the pipe, creating a column with a height of 76 cm. The level of mercury is maintained by air pressure that was exerted on the mercury contained in the vessel. As a result of experience, the amount of mercury is a measure of air pressure. Thus, to measure pressure, mercury is used mainly because it has the best properties.