Mercury-Quartz Lamp

MERCURY-QUARTZ LAMP consists mainly of an evacuated quartz tube, the ends of which terminate on both sides in extensions filled with mercury; metal electrodes connected to a current source are immersed in the latter (Fig. 1). The first mercury lamps, manufactured by Arons in 1892, had a glass tube. Subsequently, it became possible to melt rock crystal and manufacture a transparent mercury-quartz burner from it. The mercury-vapor arc formed in it produces a line spectrum composed of individual lines, which are especially numerous in the ultraviolet part of the spectrum. Practically, it can be considered that the emission spectrum of a mercury lamp does not contain infrared or red rays. Due to this, the light of such a lamp differs greatly from sunlight. Under the light of a mercury lamp, all objects, especially red ones, completely change their color. The quartz tube transmits all visible rays, as well as ultraviolet rays with a wavelength down to 180-150 mµ. Figure 1. Longitudinal section of a mercury-quartz burner.

Previous glass lamps, which were not very transparent to ultraviolet rays, transmitted only a small amount of them, and only with a wavelength down to 330-320 mµ; later, mercury lamps made of Uviol glass were released, which already transmitted a larger amount of ultraviolet rays with a wavelength down to 280 mµ. Figure 2. Spectrum of a mercury-quartz lamp. Quartz lamps are more refractory than glass ones and withstand a greater load; the increasing pressure of mercury vapors in the burner leads to an increase in the intensity of ultraviolet radiation.

Figure 3. Mercury-quartz lamp of the Jesionek type for alternating current: A-burner; B-reflector; C-transformer.

At the same time, the radiation of the mercury-quartz lamp contains a significantly larger amount of ultraviolet rays compared to sunlight, and with a shorter wavelength (in solar radiation, the shortest ultraviolet rays have a wavelength of 289 mµ) (Fig. 2). At present, mercury-quartz lamps are produced in various models. The most common is the Bach lamp (see Bach mercury-quartz lamp). The lamp according to the model of Prof. Jesionek is also widely used and is convenient for conducting group lighting. This lamp has a special reflector mounted on a stand in the shape of a truncated quadrangular pyramid, with its base facing the patient. The reflecting surface of the reflector is made of magnalium (an alloy of aluminum and magnesium), which reflects a significant part of the ultraviolet rays falling on it, thanks to which the amount of ultraviolet rays reaching the patient is increased (Fig. 3).

Figure 4. Diagram of a mercury-quartz burner for the Kromayer lamp: 1-mercury; 2-electrodes.

Figure 5. Kromayer lamp: 1-casing for the mercury-quartz burner; 2-quartz window; 3-handle for tilting the lamp during ignition; 4-electrical wires; 5 and 6-rubber tubes- inlet and outlet water for cooling.

Less frequently used at present is the mercury-quartz lamp according to Prof. Kromayer, which is used by dermatologists, dentists, and others in cases where they are limited to irradiating small surfaces, but usually, they aim to obtain a strong reaction from the illuminated skin or mucous membrane. This lamp has water cooling; thanks to this, it is possible to intensify the effect by directly pressing the lamp against the area of skin undergoing treatment (Figs. 4 and 5). All these lamps are manufactured for operation on both direct and alternating current. In the latter case, a special three-pole mercury-quartz burner is required, and in addition, a special transformer with a choke coil and rheostats is necessary; such an installation operates on the principle of a mercury rectifier. Direct current lamps are equipped only with rheostats. Until recently, we used exclusively imported burners; at present, mercury-quartz burners and the necessary fittings for them are already being manufactured in the USSR (with the exception of Kromayer lamps).

Figure 6. Self-igniting mercury-quartz burner Jaenicke: 1-mercury in the pole vessels; 2-light tube; 3-heating coil.

The power consumption when using a mercury-quartz lamp is extremely low. In recent years, new models of mercury-quartz lamps have been released that ignite automatically without tilting the burner and pouring the mercury. They are not yet widely used (Fig. 6). Mercury-quartz lamps are widely used at present in medicine, especially in cases where it is necessary to obtain an intensive effect of ultraviolet rays, predominantly rays with a shorter wavelength, i.e., those that are not contained in solar radiation or in the radiation of carbon-arc or incandescent lamps. Treatment with a mercury-quartz lamp is used for extrapulmonary tuberculosis, especially skin tuberculosis; for rickets, for poorly healing fractures, for the treatment of purulent and long-unhealing wounds and ulcers; for the treatment of a number of skin diseases (impetigo, furunculosis, psoriasis, some forms of eczema, etc.); as a method of treatment to abort erysipelas; furthermore, for general malnutrition after an infectious disease, for the treatment of neuralgia, etc.

For more details on indications and contraindications, as well as on the methodology of application and dosage, see Light therapy. On luminescent analysis in filtered ultraviolet lighting, see Wood's rays.