Example. A saturated
solution of glutamic acid (an amino acid) in water has 1.50
g of glutamic acid per 100 g of water. The observed freezing
point of the solution is -0.189íC. What is the molecular weight
of glutamic acid?
Example. A 200-mg sample
of cytochrome c (a protein) is dissolved in 10 ml of water.
The molecular weight of cytochrome c is 12,400. What is the
expected freezing point depression?
The sensitivity of molecular weight measurements can be increased
somewhat by choosing solvents with larger kf
or kb. Camphor, an
organic compound, often is used because it has a kf
of 40.0. Using molten camphor as a solvent increases the sensitivity
by more than twenty times, but this is practical only if the
molecule whose molecular weight is to be found is both soluble
in camphor and stable at the camphor melting point of 180°