Bill Potts said USMA:24400, >The kelvin is most certainly not based on the triple point, >though its relative value (between n k and n+1 k) is >equal to the that of the degree Celsius.
Well, NIST says: The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. (http://physics.nist.gov/cuu/Units/current.html) In other words, it is defined by the triple point of water, which is what I meant when I said it was "based" on the triple point. NIST further says: "The definition of the unit of thermodynamic temperature was given in substance by the 10th CGPM (1954) which selected the triple point of water as the fundamental fixed point and assigned to it the temperature 273.16 K, so defining the unit." I assumed from this that before 1954 the triple point did not figure into the definition, and therefore the definition was based on the freezing and boiling points of water. If Celsius and Centigrade have always been considered interchangeable terms for the same thing, then the differences I suggested in the last email are wrong, but I don't know of any authoritative source for this. Carl
