Near Infrared Spectrophotometric Method for the Determination of Hydration Numbers.

The 980 m absorption band of water is employed in a new method for the determination of hydration numbers. The decrease in the concentration of "free" water is calculated from the change in absorbance resulting on the addition of an electrolyte. Data are given for chromic chloride and nitrate salts in water-methanol solutions, and an extrapolation is made to give the hydration number in pure water. The results obtained by this technique agree with the values reported using other methods.