ABSTRACT
This chapter covers only lamps with “almost white colors” and good color rendering capabilities—i.e., lamps with radiation throughout the visible spectrum and discusses mercury and metal halide lamps. In metal halide lamps containing molecule vapors additional thermodynamic reactions occur—e.g., chemical dissociation and recombination of the metal halides, which participate significantly in the generation of light. Metal halide lamps are high pressure mercury lamps with metal halide additives. In general, most metal halides have higher vapor pressures than pure metals. Metal halide lamps of the type HTI with even shorter electrode spacings are used for optical purposes. Two types have been developed with an integrated dichroic reflector for use in medical and technological applications. The types of halides that offer good photometric properties cannot be used at the preferred high temperature in discharge tubes made of quartz, due to various undesirable chemical reactions of the metal halide additives with the quartz glass arc tube.
