100 



TABLE 79.— CORRECTIONS IN °C TO ADD TO BRIGHTNESS TEMPERATURE 



READINGS, FOR DIFFERENT EMISSIVITY, TO OBTAIN THE 



TRUE TEMPERATURE (concluded) 



Pyrometer using red light, wavelength, X = .665^. and c? — 14380/i °K at observed 

 temperatures degrees Kelvin, of 



TABLE 80, 



-COMPUTATION OF TOTAL EMISSIVITY VALUES FOR VARIOUS 

 GLASS SAMPLES AT LOW TEMPERATURES' 18 



Dissipating of energy by lamp bulbs.— The bulb of a 120-volt 500-watt lamp dissi- 

 pates 18.5 percent of the input energy to the lamp. About 10 percent is lost by radiation 

 and 8.5 percent by conduction and convection by the surrounding air. The losses from other 

 similar lamp bulbs probably agree with this. 



38 Barnes, B. T., Forsythe, W. E., and Adams, E. Q. Journ. Opt. Soc. Amer., vol. 37, p. 804, 1947. 

 * Assuming no radiation transmitted through sample from heater and no temperature gradient. 

 t Assuming all of sample at heater temperature. t Between front and back surfaces. 



TABLE 81.— RELATIVE EMISSIVITIES FOR TOTAL RADIATION 



Emissive power of blackbody = 1. Receiving surface platinum black at 25°C; oxidized 

 at 600 + °C. 



Temperature, °C 



200 



Silver 020 



Platinum (1) 060 



Oxidized zinc — 



Oxidized aluminum 113 



Calorized copper, oxidized 180 



Cast iron 210 



Oxidized nickel 369 



Oxidized monel 411 



Calorized steel, oxidized 521 



Oxidized copper 568 



Oxidized brass 610 



Oxidized lead 631 



Oxidized cast iron 643 



Oxidized steel 790 



400 



.030 

 .086 

 .110 

 .153 

 .185 



.424 

 .439 

 .547 

 .568 

 .600 



.710 

 .788 



600 



.038 

 .110 



.192 

 .190 



.478 

 .463 

 .570 

 .568 

 .589 



.777 

 .787 



For radiation properties of bodies at temperatures so low that the radiations of wave- 

 length greater than 20^ or thereabouts are important, doubt must exist because of the 

 possible and perhaps probable lack of blackness of the receiving body to radiations of those 

 wavelengths or greater. For instance, see Tables 568 and 573 for the transparency of soot. 



SMITHSONIAN PHYSICAL TABLES 



