What is R ?
39
Rankine
mark °R, or °Ra. (in that the need to discriminate difference, degree Rømer and Réaumur. of °Ra is used)
like grading Kelvin zero is absolute zero, but in dividing the degrees of the scale, in degrees Fahrenheit, is used so the result is °R 1 the same 1 °F, but zero degrees against 459. the 67 - Fahrenheit.
grading for use in the cycle, thermodynamic steam engines, for example, that Steam work ideal.