International Practical Temperature Scale IPTS

Primary Temperature Points Defined by the International Practical Temperature Scale (IPTS-90)... 

In 1954 the General Conference wanted to redefine the temperature scale using various primary points in addition to the two points of freezing and boiling water. The triple point of water (at 273.16 K) proved easy to obtain and very accurate (one part in a million). In 1960 the triple point of water and five other fixed points were accepted for an International Practical Temperature Scale. This scale was superseded in 1968 by the International Practical Temperature Scale (IPTS 1968), which added eight more fixed points. The current scale is shown in Table 2.29. 

The 1968 International Practical Temperature Scale (IPTS-68) relies on seven fixed points (Table 10.7). Above 1064.43°C, IPTS-68 uses Planck s equation for blackbody radiation, Eq. (5.7.4). 

The temperature at which a particular event occurs, or the temperature range over which a reaction happens, are often characteristic of the nature and history of a sample, and sometimes of the methods used to study it. Sharp transitions, such as the melting of pure materials, may be used to calibrate equipment and as the fixed points of thermometry and of the International Practical Temperature Scale (IPTS). 

The platinum resistance thermometer is the interpolating instrument for the International Practical Temperature Scale, IPTS-48 and as revised, IPTS-68. IPTS-48 used the Callendar equation,... 

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