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.
