Dilute nitric, sulfuric, and perchloric acids are applicable as solvents for spectrophotometry up to 250°C over the following ranges: 0 to 1.0 f HNO3 from 0.6 to 1.2 μ; 0 to 0.2 f H2SO4 from 0.25 to 1.2 μ; and 0 to 1.0 f DClO4 from 0.25 to 1.8 μ. Each of these acids reacts measurably with the titanium cell wall and the sapphire windows at rates which increase with acidity and temperature. This corrosion affects the spectral measurements as a function of time and is associated with deterioration of cell window surfaces and the presence in the sample of dissolved and suspended corrosion products. These results are part of our more general program for the development of equipment and technique for routine spectrophotometry of pure liquids and solutions over a wide range of temperature and pressure.
W. C. Waggener, A. J. Weinberger, and R. W. Stoughton, "Spectrophotometry of Aqueous HNO3, H2SO4, and DClO4 from 25° to 250°C," Appl. Spectrosc. 22, 545-548 (1968)