320 



Tables 318 and 319 



radiation emissivities 



TABLE 318. — Relative Emissive Powers for Total Radiation 



Emissive power of black body = i. Receiving surface platinum black at 25 C; oxidized surfaces oxidized at 

 600 + ° C. Randolph and Overholzer, Phys. Review, 2, p. 144, 1913. 



Silver 



Platinum (1) 



Oxidized zinc 



Oxidized aluminum 



Calorized copper, oxidized 



Cast iron 



Oxidized nickel 



Oxidized monel 



Calorized steel, oxidized. . 



Oxidized copper 



Oxidized brass 



Oxidized lead 



Oxidized cast iron 



Oxidized steel 



Black body 



Temperature, Deg. C 



0.020 

 0.060 



0.113 



0.180 

 0.210 

 0.369 

 0.41 1 

 0.521 

 0.568 

 0.610 

 0.631 

 0.643 

 o. 790 

 1 .00 



Remark: For radiation properties of bodies at temperatures so low that the radiations of wave length 

 greater than 20/x 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 wave lengths or greater. For 

 instance, see Tables 455 and 460 for the transparency of soot. 



TABLE 319. — Emissivities of Metals and Oxides 



Emissivities for radiation of wave-length 0.55 and 0.65 fx. Burgess and Waltenberg, Bui. Bureau of Standards, 

 11, 591, 1914. 



In the solid state practically all the metals examined appear to have a negligible or very small temperature coeffi- 

 cient of emission for X = 0.55 and 0.65 ix within the temperature range 20° C to melting point. Nickel oxide has a 

 well-defined negative coefficient, at least to the melting point. There is a discontinuity in emissivity, for X = 0.65 fx 

 at the melting point for some but not all the metals and oxides. This effect is most marked for gold, copper, and 

 silver, and is appreciable for platinum and palladium. Palladium, in addition, possesses for radiation a property 

 analogous to suffusion, in that the value of emissivity (X = 0.65 fj.) natural to the liquid state may persist for a time 

 after solidification of the metal. The Violle unit of light does not appear to define a constant standard. Article con- 

 tains bibliography. 



Smithsonian Tables. 



