300 



Tables 363-365. 



REFLECTING POWER. 



TABLE 363. — Reflecting Power of Powders (White Light). 



Various pure chemicals, very finely powdered and surface formed by pressing down with glass plate. White (noon 

 sunlight) light. Reflection in per cent. Nutting, Jones, Elliott, Tr. 111. Eng. Soc. 9, S93, 1914. 



Aluminum oxide 83 . 6 



Barium sulphate 81. i 



Borax 81.6 



Boric acid 83 . 2 



Calcium carbonate 83 . 8 



Citric acid 81.5 



Magnesium carbonate 86 . 6 



(block) 88.0 



Magnesium oxide 85 . 7 



Rochelle salt 79-3 



Salicylic acid 81. i 



Sodium carbonate 81.8 



Sodium chloride 78. i 



Sodium sulphate 77. & 



Starch 80.3 



Sugar 87 . 8 



Tartaric acid 79. i 



TABLE 364. — Variation of Reflecting Power of Surfaces with Angle. 



Illumination at normal incidence, ij watt tungsten lamp, reflection at angles indicated with normal. 111. Eng. Soc., 

 Glare Committee, Tr. 111. Eng. Soc. 11, p. 92, 1916. 



Angle of observation. 



do- 



Magnesium carbonate block 



Magnesium oxide 



Matt photographic paper . . , 



White blotter 



Pot opal, ground 



Flashed opal, not ground . . , 



Glass, fine ground 



Glass, course ground 



Matt varnish on foil 



Mirror with ground face. . . . 



0.69 

 [1-3 

 o. 29 



0.78 



0.80 

 0.78 

 o. 76 

 0.69 



0.31 



o. 29 



O. 20 



o. 72 

 4SS 



0.80 

 0.78 



o. 76 

 0.69 



O. 22 



o. 27 

 o. ig 

 0.62 



0.87 

 0,80 

 0.78 



o. 76 

 0.69 



o. 16 

 O 49 

 3 03 



0.83 



0.77 

 0.78 

 .0.73 

 0,68 

 o. 20 



0.72 



0.7s 



o. 76 

 o. 70 

 0.66 

 o. 20 



013 



o. ri 

 0.21 

 0.42 



0.66 

 0.72 

 0.67 

 0.64 

 0.18 

 0.12 

 0.12 

 0.16 

 0.3s 



The following figures, taken from Fowle, Smithsonian Misc. Col. 58, No. 8, indicate the amount of energy 

 scattered on each side of the directly reflected beam from a silvered mirror; the energy at the center of the 

 reflected beam was taken as 100,000, and the angle of incidence was about 3°. 



Angle of reflection, 3° 

 Energy 



Wave-length of max. energy of Nemst lamp used as source about 2/1. 



TABLE 365. — Infra-red Reflectivity of Tungsten (Temperature Variation). 



Three tungsten mirrors were used, — a polished Coolidge X-ray target and two polished flattened wires mounted 

 in evacuated soft-glass bulbs with terminals for heating electrically. Weniger and Pfund, J. Franklin Inst. 



See also Weniger and Pfund, Phys. Rev. 15, p. 427, 1919. 



Smithsonian Tables. 



