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A mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube. Mercury vapor lamps are more energy efficient than incandescent and most fluorescent lights, with luminous efficacies of 35 to 65 lumens/watt. Their other advantages are a long bulb lifetime in the range of 24,000 hours and a high intensity, clear white light output.〔 For these reasons, they are used for large area overhead lighting, such as in factories, warehouses, and sports arenas as well as for streetlights. Clear mercury lamps produce white light with a bluish-green tint due to mercury's combination of spectral lines.〔 This is not flattering to human skin color, so such lamps are typically not used in retail stores.〔 "Color corrected" mercury bulbs overcome this problem with a phosphor on the inside of the outer bulb that emits white light. They offer better color rendition than the more efficient high or low-pressure sodium vapor lamps. They operate at an internal pressure of around one atmosphere and require special fixtures, as well as an electrical ballast. They also require a warm-up period of 4 – 7 minutes to reach full light output. Mercury vapor lamps are becoming obsolete due to the higher efficiency and better color balance of metal halide lamps. ==Origins== Charles Wheatstone observed the spectrum of an electric discharge in mercury vapor in 1835, and noted the ultraviolet lines in that spectrum. In 1860, John Thomas Way used arc lamps operated in a mixture of air and mercury vapor at atmospheric pressure for lighting.〔Maxime F. Gendre (Two Centuries of Electric Light Sources Innovations ). p. 4. (PDF) . Retrieved on 2012-01-02.〕 The German physicist Leo Arons (1860–1919) studied mercury discharges in 1892 and developed a lamp based on a mercury arc.〔Clement D. Child '' Electric Arcs-Experiment Upon Arcs Between Different Electrodes in Various Environments'', reprint by Watchmaker Publishing, 2002 ISBN 0-9726596-1-7, p. 88〕 The first mercury vapor lamp to achieve widespread success was invented in 1901 by American engineer Peter Cooper Hewitt.〔(【引用サイトリンク】publisher=Encyclopædia Britannica )〕 Hewitt was issued on September 17, 1901.〔(【引用サイトリンク】publisher=United States Patent and Trademark Office )〕 In 1903, Hewitt created an improved version that possessed higher color qualities which eventually found widespread industrial use.〔 The ultraviolet light from mercury vapor lamps was applied to water treatment by 1910. The Hewitt lamps used a large amount of mercury. In the 1930s, improved lamps of the modern form, developed by the Osram-GEC company, General Electric company and others led to widespread use of mercury vapor lamps for general lighting. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mercury-vapor lamp」の詳細全文を読む スポンサード リンク
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