Allow me to correct my own error before others notice it. The zero on the "Celsius" scale is 273.15 kelvin, not 273.16 kelvin. (NIST SP 811, page 5)
These temperatures are, however, correctly stated as the "ice point" and the "tripple point" respectively, and the "tripple point" is more accurately realized in laboratories, as stated below. The subtle difference between the centigrade and Celsius scales is not so simply explained as I attempted to do below. What is the difference? Gene. ....................................... On Sat, 2 Mar 2002, Gene Mechtly wrote: > On Thu, 28 Feb 2002, Stephen Davis asked: > > > ... why Centigrade was replaced by Celsius!! > > Steve, > > The kelvin scale of temperature is *defined* by fixing a *single* > reference temperature, the "triple point" temperature of pure water, > at exactly 273.16 kelvin. (where "triple point" means the temperature > of ice, water, and water vapor in equilibrium) > > > The zero on the Celsius scale is fixed at the "triple point" of water; > at 273.16 kelvin. > > On the other hand, the zero on the centigrade scale had been set at > the "ice point" of water, at 273.15 kelvin. (the temperature of melting > ice) > > Although the difference is only 0.01 kelvin, the "triple point" is more > accurately realized in laboratories than the "ice point", and therefore > the Celsius scale is preferable to the centigrade scale. > > See Resolution 3 of the 9th CGPM of 1948, Page 122 in the BIPM Booklet. > > Gene. >
