History
The first clinically useful osmometer used the freezing point method and was available in the 1950’s, while a vapor pressure osmometer was available starting in the 1970’s.

Direct osmolality measurements are usually performed by freezing point or vapor pressure depression osmometers. Both instruments can provide reliable measurement of osmolality. However, freezing point depression osmometry is capable of measuring all osmotically active solutes, including volatile substances, making it the most sensitive and accurate technology available.