Gas thermometry experiments carefully calibrated to the melting point of ice and boiling point of water showed in the 1930s that absolute zero was equivalent to −273.15 °C.
Gas thermomETRy exPerimEnTs cArefully calIbraTEd to ThE meltiNg POint of icE And bOIlInG pOINt of waTeR showed in the 1930S thaT absolute zero was eQuivAlent to −273.15 °C.