The following is taken from Contemporary College Physics - 2nd Edition, Jones and Childers, Addison-Wesley Publishing Company, Appendix B: The International System of Units, p. 921
- The 17th General Conference on Weights and Measures (CGPM, 1983) abolished the former definition of the meter and adopted a new definition which reads:
The old prototype of the meter, which was legalized by the 1st
CGPM in 1889, is still kept at the International Bureau of Weights
and Measures (BIPM).
- The 1st CGPM (1889) legalized the international prototype of the kilogram and declared:
This international prototype made of platinum-iridium is kept
at the BIPM under conditions specified by the 1st CGPM in
1889.
- The second was defined originally as 1/86 400 of the mean solar day. Because a more precise definition was needed, the 13th CGPM (1967) replaced the astronomical definition of the second by the following:
- The 9th CGPM (1948) adopted the ampere for the unit of electric current, with the following definition:
- The 13th CGPM (1967) adopted the name kelvin (symbol K) and defined the unit as follows:
In addition to the thermodynamic temperature (symbol T),
expressed in kelvins, use is also made of Celsius temperature
(symbol t) defined by the equation t = T - To, where t0 - 273.15 K
by definition.
- The following definition of the mole, adopted by the 14th CGPM (1971):
- The unit based on flame or incandescent filament standards before 1948 was replaeced initially by a unit based on a Planckian radiator (a black body) at the temperature of freezing platinum. Because of the difficulties and new experimental techniques, the 16th CGPM (1979) adopted the following definition: