| Table 1. Defining Fixed Points of the ITS-90 | |||||
| Number | Temperature | Substance a | State b | Wr (T90) | |
| T90/K | t90/°C | ||||
| 1 | 3 to 5 | -270.15 to -268.15 | He | V | |
| 2 | 13.8033 | -259.3467 | e-H2 | T | 0.001 190 07 |
| 3 | ~17 | ~-256.15 | e-H2 (or He) | V (or G) | |
| 4 | ~20.3 | -252.85 | e-H2 (or He) | V (or G) | |
| 5 | 24.5561 | -248.5939 | Ne | T | 0.008 449 74 |
| 6 | 54.3584 | -218.7916 | O2 | T | 0.091 718 04 |
| 7 | 83.8058 | -189.3442 | Ar | T | 0.215 859 75 |
| 8 | 234.3156 | -38.8344 | Hg | T | 0.844 142 11 |
| 9 | 273.16 | 0.01 | H20 | T | 1.000 000 00 |
| 10 | 302.9146 | 29.7646 | Ga | M | 1.118 138 89 |
| 11 | 429.7485 | 156.5985 | In | F | 1.609 801 85 |
| 12 | 505.078 | 231.928 | Sn | F | 1.892 797 68 |
| 13 | 692.677 | 419.527 | Zn | F | 2.568 917 30 |
| 14 | 933.473 | 660.323 | Al | F | 3.376 008 60 |
| 15 | 1234.93 | 961.78 | Ag | F | 4.286 420 53 |
| 16 | 1337.33 | 1064.18 | Au | F | |
| 17 | 1357.77 | 1084.62 | Cu | F | |
a All substances except 3He are of natural isotopic composition, e-H2 is hydrogen at the equilibrium concentration of the ortho- and para-molecular forms. b For complete definitions and advice on the realization of these various states, see "Supplementary Information for the ITS-90". The symbols have the following meanings: V: vapour pressure point; T: Triple Point (temperature at which the solid, liquid and vapour phases are in equilibrium); G: gas thermometer point; M,F melting point, freezing point (temperature, at a pressure of 101 325 Pa, at which the solid and liquid phases are in equilibrium) | |||||