Osmolality/osmolarity data and calculations

In view of the increasing interest in the osmolarity of parenteral solutions, an extensive compilation of pertinent numerical data is described. This compilation tabulates values of density, molar concentration, freezing point lowering,real osmolality, and molar concentration of the isotonic sodium chloride solution for 99 compounds, two-thirds of which are of use in pharmacy. A wide range of concentrations is covered for each compound, the values being listed in increments of 0.50, 1.00, or 2.00 percent w/w. Simple equations to convert molar into molal concentrations and to correlate freezing point lowering, osmotic pressure, osmolality and molality are presented. The practical use and theoretical meaning of the osmotic coefficient are discussed. As an example of a solution with several solutes, the real osmolality and osmolarity of Ringer's Solution is computed from the tabulated values of the freezing point depressions of the component salts.