A simple instrument for ultraviolet-visible absorption spectrophotometry in high temperature molten salt media

Abstract

An inexpensive (<US$5000) spectrophotometer of simple design was constructed from commercially available components for absorption spectroscopic studies in molten chloride salts. The spectrometer consists of a replaceable fused silica cell of 9×9 mm square exterior cross-section housed in a temperature-controlled ceramic tubular furnace of 13 mm inner diameter. Light communication to and from the cell occurs via a pair of 1 mm core silica-on-silica optical fibers from diametrically opposite sides. The light source is a pulsed xenon flash lamp and detection is accomplished by a photodiode array spectrometer card housed in a personal computer. The system has been operated up to temperatures of 950 °C. The effective spectral range is 280–650 nm at 900 °C; higher wavelengths can be accessed at lower operating temperatures. A spectral snapshot can be acquired in as little as 1 ms. With 1 s integration time, the intrinsic system noise level is ∼2×10−4 absorbance units. The system is compact and energy efficient. Applications of the system are demonstrated with spectral studies of some metal chloride systems in an equimolar sodium and potassium chloride eutectic.