The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of
mercury at and standard gravity (
gn = ). It was used as a reference condition for physical and chemical properties, and the definition of the
centigrade temperature scale set 100 °C as the boiling point of water at this pressure. In 1954, the 10th
General Conference on Weights and Measures (CGPM) adopted
standard atmosphere for general use and affirmed its definition of being precisely equal to
dynes per
square centimetre (). This defined pressure in a way that is independent of the properties of any particular substance. In addition, the CGPM noted that there had been some misapprehension that the previous definition (from the 9th CGPM) "led some physicists to believe that this definition of the standard atmosphere was valid only for accurate work in
thermometry." ==Pressure units and equivalencies ==