In 1960 David and Ewald [1] developed a technique for photographing the absorption spectra of solutions under shock wave conditions. A photograph of the spectrum of a uranyl nitrate solution exposed to a shock wave of 75 kbar showed the absorption to extend beyond 500 nm, the long wavelength limit for uranyl solutions under ordinary conditions. A.H. Ewald (unpublished, 1963) found that at room temperature pressure up to 6 kbar had no appreciable effect on absorption. Bell and Biggers [2,3] published an analysis of the spectrum of uranyl perchlorate solutions. The longest wavelength absorption band was at 486 nm but Bell [4] later found bands at 508 and 531 nm. The intensity of these very weak bands increased when the solution was heated to 95° C, and they were interpreted as “hot bands” due to absorption from an excited ground state. This paper reports new absorption measurements made on uranyl solutions heated to 250°C at low pressure and offers an interpretation of the effect observed in the shock experiments.