Modifications to the Hitachi Perkin–Elmer 139 ultraviolet–visible spectrophotometer are described which enable absorption spectra of molten salts to be measured to 865 °C. The instrument can be readily reconverted for ambient temperature measurements. The solubilities and the limiting heats of solution of Ag2CrO4and PbCrO4in equimolar NaNO3–KNO3have been measured spectrophotometrically from 250 to 350 °C. The absorption spectrum of dilute solutions of Cr(III) in CsCl has been measured, the octahedral CrCl63−being present in solution at 700 °C.