Electric lamps high-pressure mercury

Lemington H.26X., made by the General Electric Co., is a very hard borosilicate glass of high softening temperature. Tte Mg point is 780°C. It is used in high pressure mercury vapour lamps. The linear expansion coefficient is 4-6 x 10 from 20 to 580°C. Sodium and potassiiun are absent and alumina is present in quantity in this glass. 

Measurement of Photochemical Reactivity. The polymer solution in THF was cast on a KRS plate and dried. The film obtained on the plate was irradiated by a high-pressure mercury lamp (Ushio Electric Co USH-250D) without a filter at a distance of 30 cm in air. The rate of disappearance of the C=C bonds at 1640 cm 1 was measured by IR spectrometry (JASCO A-202 model). 

Ultraviolet intensity is easily controlled through the selection of the lamp. Low-pressure mercury cathode lamps emit most of their energy at the optimal wavelength of 253.7 nm. The electrical input ranges from 15 to 30%. The advantage of medium-pressure, mercury-vapor lamps is their high electrical rating from 0.1 to 20 kW. However, medium-pressure mercury lamps have... 

The checkers used a 275-watt General Electric sunlamp. The submitters indicate that the type of sunlamp is not critical and that a 125-watt Philips E99/2 sunlamp or a 125-watt Philips 57203 high-pressure mercury lamp are suitable. If the heat from the sunlamp does not maintain reflux, the reaction flask should be about one-fourth submerged into a hot oil bath. 

On the other hand, medium-pressure (MP) Hg lamps can be operated with much higher electrical input power up to 30 kW, but with a reduced UV radiant power efficiency of 30 to 40%. Their dimensions are more compact than the dimensions of the LP Hg lamps, but their polychromatic emission ranges from the UV (UV-C - 15-23%, UV-B - 6-7 %, UV-A - 8%) over the VIS (-15%) to the IR (-47-55%) region of the electromagnetic spectrum (e.g. McClean, 2001). Lam-brecht (1999) reported the power balance of electromagnetic radiation of an industrially used high-pressure mercury lamp with a power density of 200 W cm as follows 13.2% UV-C, 7.15% UV-B, 7.15% UV-A, 21% VIS, and 14% IR... 

B) Data Analysis. Irradiation was performed with a high pressure mercury lamp (250W, Ushio Electrics Co.). The two dichroic absorbance components of HNMA and Cyclophane at 393.5tun and 402nm were monitored at room temperature after irradiating the sample over different time intervals with linearly polarized light at 365nm. The reorientation dynamics of these molecular tracers were obtained from the analysis of the time-dependent induction efficiency qft) which is defined as" r (t) = 100. ODx(t) - ODii (t) /ODo (1)... 

Apart for the use of lasers, which may be advantageous in a suitably built apparatus, irradiation is usually done by means of a mercury arc. A worry when considering a photoreaction is the high price of the lamp and the (monetary and environmental) cost incurred for the electrical power required. As one can see from the literature, high-pressure mercury arcs are often satisfactorily general-purpose sources and many laboratories use 400-500 W lamps of this type. These are in fact somewhat expensive and with a limited lifetime (hundreds of hours). However, 125-150 W mercury arcs are often... 

General Electric AH-6 high pressure mercury arc lamp. 

The high-pressure mercury lamp [Model UM-102, Ushio Electric Inc. (Japan)l emits the UV spectrum... 

Other sources are incandescent electric lamps (tungsten), the Welsbach mantle, hot glass, and the quartz-jacketed high-pressure mercury arc. The tungsten ribbon filament lamp makes a good secondary standard (compared to a primary blackbody) in the near... 

Mercury is directly below cadmium in the periodic table, but has a considerably more varied and interesting chemistry than cadmium or zinc. Elemental mercury is the only metal that is a liquid at room temperature, and its relatively high vapor pressure contributes to its toxicological hazard. Mercury metal is used in electric discharge tubes (mercury lamps), gauges, pressure-sensing devices, vacuum pumps, valves, and seals. It was formerly widely used as a cathode in the chlor-alkali process for the manufacture of NaOH and Cl2, a process that has been largely discontinued, in part because of the mercury pollution that resulted from it. 

Mercury-xenon lamp (Arc) An intense source of ultraviolet, visible, and near infrared radiation produced by an electrical discharge in a mixture of mercury vapor and xenon under high pressure. 

In this review of the high pressure sodium lamp, emphasis is placed on evidence concerning the interaction of resonantly excited sodium atoms with sodium, mercury or xenon atoms, which modifies the spectral radiance of lamps to improve the color or efficacy. The influence of mercury and xenon buffer gases on tne thermal and electrical conductivities and hence on lamp efficacy are also indicated. 

A high-intensity, electrodeless ultraviolet source has recently been introduced. This UV source is distinguished from other conunercially available UV lamps by the fact that no electrodes are Inside the lamp. Electrical energy is supplied in the form of radio frequency power that is coupled into an evacuated quartz tube containing mercury and other additives. As compared to conventional medium-pressure mercury arcs with electrodes, the electrodeless system has several attributes that make it unique (17). These are summarized as follows (1) instant on-off (2) modular lamp design (3) increased lamp lifetime (4) variable spectrum (5) excellent energy conversion. 

Mercury or xenon arc lamps are used. A schematic of a xenon arc lamp is given in Fig. 5.42. The quartz envelope is filled with xenon gas, and an electrical discharge through the gas causes excitation and emission of light. This lamp emits a continuum from 200 nm into the IR. The emission spectrum of a xenon arc lamp is shown in Fig. 5.43. Mercury lamps under high pressure can be used to provide a continuum, but low-pressure Hg lamps, which emit a line spectrum, are often used with filter fluorometers. The spectrum of a low-pressure Hg lamp is presented in Fig. 5.44. 

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