The values of Kf and Kb, which depend upon the nature of the
solvent, can be ascertained from the following relations Kf
=
2
1
f
fus
 × 
 × 
1000 × 
R
M
T
H
(1 37)
Kb
=
2
1
b
vap
 × 
1000 ×  × 
R
M
T
H
(1 38)
Here the symbols R and M1 stand for the gas constant and molar
mass of the solvent, respectively and Tf and Tb denote the freezing point
and the boiling point of the pure solvent respectively in kelvin