An absolute temperature scale is independentof the properties of the substances.The temperatures are always measured by making use of properties e.g. thermal expansion of liquids and gases, the variation of thermo e.m.f. and electrical resistance with temperature etc.
Lord kelvin from the study of the effeciency of reversible engion could define a new scale of temperature which a independent of the particular substance because the efdficency of a reversible engion itself is independent of the working substance
6.2 The Thermodynamic Temperature Scale;-
suryakanu.blogspot.comso that the ratio of the heat exchanged is a function of the temperature. We could choose any function that is monotonic, and one choice is the simplest: . This is the thermodynamic scale of temperature, . The temperature defined in this manner is the same as that for the ideal gas; the thermodynamic temperature scale and the ideal gas scale are equivalent..