Robert Bushnell in USMA 18771 confuses a change of name with a change of
definition:
>This list has discussed centigrade and Celsius. It has been said that
>the values are the same.
>The Celsius and centigrade temperature scales are defined differently.
>There may be small differences in values.
>
>Centigrade has 0 defined as the freezing temperature of water and has 100
>defined as the boiling temperature of water, both at STP.
>
>Celsius has 0 defined as 273.15 K and increments are kelvins.
>
>So zero degrees Celsius may not be the freezing temperature of water and
>100 degrees Celsius may not be the boiling temperature of water.
>An increment of one degree centigrade may not be an increment of one kelvin.
>
>For use by standards laboratories, the definitions are different so the
>values may not be the same. Result: for temperature, in SI centigrade
>does not exist.
>
> Robert Bushnell
I found that the centigrade scale was called Celsius when I visited Germany
in 1936. The BBC was still calling it "centigrade" in the 1980s. On page
123 of the BIPM bible we find "
"*CIPM, 1948 and 9th CGPM, 1948: adoption of "degree Celsius"8
"From the three names ("degree centifrade", "centesimal degree", "degree
Celsius") proposed to denote the degree of temperature, the CIPM has chosen
"degree Celsius (PV, 21, 88).
"This name is also adopted by the 9th CGPM (CR, 64)."
That is the history of the name change, which had nothing to do with the
physical definition . The change in the physical definition did not take
place until 1954, this is six years later.
"*10th CGPM, 1954, Resolution 4 (CR, 79): definition of the thermpdynamic
temperature scale*
"The 10th Conf�rence G�n�rale des Poids et Mesures decides to define the
thermodynamic temperature scale by choosing the triple point of water as
the fundamental fixed point, and assigning to it the temperature of 273.16
degrees Kelvin exactly."
"*The 13th CGPM, 1967-1968, Resolution 3: SI unit of thermodynamic
teperature (kelvin)*
.............................................................................
3. a temprature interval may also be expressed in degrees Celsius;
Resolution 4 decided:
"The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of
the thermodynamic temperature of the triple point of water."
I apologize for repeating what I wrote some months ago.
Joseph B.Reid
17 Glebe Road West
Toronto M5P 1C8 TEL. 416-486-6071
