During the operation of a fluorescent lamp mercury chemically combines with various components inside the lamp. For some types of lamps most of the bound mercury is observed to reside in the glass, despite the intervening phosphor layer. This consumption of mercury by the glass only occurs when a mercury/rare-gas plasma is present. Experiments were performed to isolate the various factors arising from the operation of the plasma in order to determine which ones are important in driving mercury consumption in the glass. These experiments include shielding samples from the plasma, measuring the line-of-sight transmission of the phosphor, and applying small radial de electrical biases to the lamp. In addition, various analytical techniques, including x-ray photoelectron spectroscopy, Rutherford baekscattering, scanning electron microscopy, and thermally stimulated evolution where used to study the glass surface after exposure to a mercury/ rare-gas plasma. From these studies it is postulated that electrochemical effects play a major role in binding mercury to the glass.

Mercury vapor is essential to the high efficiency conversion of electrical power to light in fluorescent lamps. However, the amount of mercury that must be added to the lamp to achieve a 20,000 h operating life is much larger than the amount of vapor needed for the discharge. This is a result of processes that bind the mercury during lamp operation and make it unavailable as mercury vapor. As part of an effort to determine the amount of mercury that must be added to standard GE F40TI2 lamps with halophosphate phosphors we have measured the mercury bound in the soda-lime glass under the phosphor in the positive column in a series of these lamps. From these measurements we have developed an empirical model which describes the amount of mercury per unit area that is bound in the glass as a function of operating time and the weight of phosphor over the glass.