140 BIOPHYSICALLY ACTIVE LIGHT 



lengths: 2536, 2652, 2894, 2967, 3021, and 3130 A; less strongly at 

 2752 and 2804 A; and weakly at 2378, 2399, 2482, and 2698 A. The 

 newer high-potential " SC-2537 Hanovia " mercury-vapor arc has as 

 much as 85 per cent or more of its energy of emission concentrated at 

 2537 A. 



" Sterilamp " 



This lamp was designed and constructed by the Westinghouse Lamp 

 Company to emit its predominant radiations at wavelengths having 

 the highest bactericidal properties and the least erythemal effect. Radi- 

 ations from these lamps produce a mercury spectrum with the greater 



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portion of the radiant energy in the region of 2537 A. There is also 

 some radiation in the region of 1849 to 1960 A. The shortest radiations 

 are readily absorbed by the surrounding air but are very strong in 

 bactericidal action. 



These lamps are tubular and are made in various lengths. A typical 

 example has an overall length of 14 in. and a f -in. diameter. Its start- 

 ing potential is 400 volts alternating current, operating, however, at 

 275 volts with a current of about 0.03 amp. They have two terminals, 

 one at each end, and burn in any position when connected to the 110- 

 volt a-c circuit with proper transformers. Hart and Gardner [1937] and 

 others have used this type of lamp for sterilization of the air in the 

 surgical operative region. 



" Sunlight Lamp " 



Of the number of tungsten-mercury arcs that have been patented, the 

 only one which has been commercialized is the sunlight (Type S-l) 

 lamp, developed by the General Electric Company. It consists of two 

 tungsten button electrodes at the terminals of a tungsten filament sup- 

 port, as shown in Fig. IV-3, a pool of mercury, and an argon-filled 

 " Corex D Glass " globe. The lamp starts in any position. When the 

 proper voltage is applied, the filament heats and the arc strikes between 

 the button terminals. The biologically active radiation becomes more 

 intensive as the bulb increases in temperature. It is essentially a low- 

 voltage lamp, and the attached transformer must deliver 9.5 amp at 

 approximately 30 volts in order to heat the filament. When the arc is 

 completed, the current rises to 30 amp and the voltage drops to about 

 11 volts. The lamp consists of two primary sources of energy, incan- 

 descent tungsten and mercury vapor. The emitted radiant energy of 

 the former consists of a continuous spectrum of all wavelengths extending 



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from the long-wave infra-red to about 3500 A in the violet region. The 



