60 HADIATION HIOI-OC.Y 



per steradiiui is uii unsatisfactory description of the output of linear 

 sources. 



2050 A i:cn IVALKVCE 



Since 25;i7 A (Micrj>;y has only about 85 per cent of the hactcricidal 

 action of 2050 A energy (Table 2-1), the ultraviolet watts output and 

 ultraviolet microwatts of Table 2-3 must be multiplied by 0.85 for the 

 2050 A bactericidally equivalent ultraviolet watts of Table 2-0. 



INTENSITY 



RELATIVE ENERGY DISTRIBUTION 



The inherent spectra of all low-pressure mercury arcs are dominated 

 by the 2537 and 1849 A lines. Other lines are so relatively weak and 

 from such low-intensity sources that they are of little practical value 

 (Table 2-5 and Fig. 2-56). The output of the 1849 A line is determined 



Table 2-5. Relative Energy in Various Spectral Lines or Groups of 



Typical Low-pressure Lamps 



Wave Length, A Relative luiergy, % 



2537 100 



2652 0.14 



2753-2893 0.12 



2967 . 37 



3022 0.17 



3126-3132 1.43 



3650-3()63 1 . 30 



3906-4077 1 . 60 



4339-4358 3 . 40 



5461 2.25 



5770-5791 0.60 



over a wide range by the fused cjuartz and the special glasses, in various 

 thicknesses, whose transmissions are shown in Fig. 2-5a. Since the 

 1849 A energy is rapidly absorbed by air (about 50 per cent in 1 in.) and 

 since it penetrates licjuids and cellular proteins much less effectively than 

 the 2537 A, little practical bactericidal application has been found for 

 energy of this wave length. Since 1849 A energy is only slightl}^ absorbed 

 by nitrogen but is readily absorbed by oxygen, it provides ozone in air, 

 relatively uncontaminated by oxides of nitrogen, and some practical 

 application of this energy for this purpose is being made. Commercially 

 available sources in thin glass provide 1849 A energy to an extent 1-2 per 

 cent that of 2537 A energy. Greater 1849 A energy output is possible 

 through thin fused-fjuartz glass. 



RESEARCH SPECIFICATIONS OF ULTRAVIOLET INTENSITY 



The ultraviolet power output and intensity ratings of Table 2-3 are 

 average values for new sources. The variation and service depreciation 



i 



