Table 372. 20^ 



TRANSMISSIBILITY OF RADIATION. 



Transmlsslbllity of the Various Substanceg of Tables 330 to 338. 



Alum : Ordinary alum (crystal) absorbs the infra-red. 



Metallic reflection at 9.05/t and 30 to 40/i. 

 Rock-salt : Rubens and Trowbridge (Wied. Ann. 65, 1898) give the following transparencies for 

 a I cm. thick plate in % : 



Pfliiger (Phys. Zt. 5. 1904) gives the following for the ultra-violet, same thickness : zSofi/i, 95.5% ; 



231,86%; 210,77%; 186,70%. 

 Metallic reflection at o.iioyu, 0.156, 51.2, and 87/*. 

 Sylvite: Transparency of a i cm. thick plate (Trowbridge, Wied. Ann. 60, 1S97). 



Metallic reflection at o.ii4ju, 0.161, 61. i, 100. 

 Fluorite : Very transparent for the ultra-violet nearly to o.i^i. 

 Rubens and Trowbridge give the following for a i cm. plate (Wied. Ann. 60, 1897) : 



Metallic reflection at 24//, 31.6, 40 fi. 

 Iceland Spar: Merritt (Wied. Ann. 55, 1895) gives '^^ following values of k in the formula 

 i= i„e~'"' (d in cm.) : 

 For the ordinary ray : 



Quartz : Very transparent to the ultra-violet ; Pfliiger gets the following transmission values for 

 a plate i cm. thick : at 0.22 2;u, 94.2% ; 0.214,92; 0.203,83.6; 0.186,67.2%. 

 Merritt (Wied. Ann. 55, 1895) gives the following values for k (see formula under Iceland Spar) : 

 For the ordinary ray : 



For X>7 /It, becomes opaque, metallic reflection at 8.50/4, 9.02, 20.7 5-24.4JU, then trans- 

 parent again. 



The above are taken from Kayser's " Handbuch der Spectroscopie," vol. iii. 

 Smithsonian Tables. 



