ABSTRACT
INTRODUCTION In metal halide lamps in which a sufficiently high salt dose is present, the metal halide components form a saturated vapour directly above the position of the excess salt that is present in liquid form, the salt pool. The plasma temperature distribution, the gas convection pattern and the temperature of the salt pool determine the partial pressures of the compounds in the discharge tube. In first instance, assuming the thermodynamical data of the salt mix are available, only the pressures above the salt pool are known. To obtain a rough estimate of the partial component pressures pa in the discharge tubes, without using very complex transport models, the pressures are calculated as a function of the temperature by using far-reaching simplifications.
