HYDRONIUM ION ABSORPTION IN THE REGION 1.7 µ

Abstract
Optical absorption of the hydronium ion in the region 1.7 µ was measured in solutions of nitric acid and perchloric acid in the concentration range 0.01 to 4.0 moles per liter. Above 0.1 molar the absorption did not follow Beer's Law, being smaller than predicted from the low concentration behavior. This enhanced transparency is attributed to a "negative absorption" band, associated with the change in solvent structure, found in this spectral region.