In reading Atkins' Physical Chemistry, the first section of the first Chapter, the author says that the conversion equation between the absolute temperature and celsius is exact and at the same time the author explains that the Kelvin is defined by setting the triple point as 273.16 [K], and it happens to be the melting point of water is 0.01[K] under this point. How can this be exact? At the first glance ,if Celcius is defined with the melting point and boiling point setting as 0 and 100, it should be empirical.

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    $\begingroup$ As Kelvin scale was redefined via the Planck constant and as Celsius scale was redefined to keep following the former by 273.15 offset, the standard water melting and boiling point does not exactly match 0 and 100 deg C. But it does for very most practical purposes. See more at wikipedia - Kelvin $\endgroup$
    – Poutnik
    Commented May 13, 2022 at 6:40
  • $\begingroup$ chemistry.stackexchange.com/questions/122828/… $\endgroup$
    – Mithoron
    Commented May 13, 2022 at 13:03


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