39° 



Table 446 



TRANSPARENCY OF THE VARIOUS SUBSTANCES OF 

 TABLES 394 TO 402 



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



Metallic reflection at 9.05/1 and 30 to 40/t. 

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

 a 1 cm. thick plate in % : 



Pfliiger (Phys. Zt. 5. 1904) gives the following for the ultra-violet, same thickness : 280/1/1, 95.5% ; 



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

 Metallic reflection at o.uo/i, 0.156, 51.2, and 87/t. 

 Sylvite : Transparency of a 1 cm. thick plate (Trowbridge, Wied. Ann. 60, 1897). 



Metallic reflection at 0.1141*, 0.161, 61. 1, 100. 

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



Rubens and Trowbridge give the following for a 1 cm. plate (Wied. Ann. 60, 1897) 



Metallic reflection at 24/1, 31.6, 40/1. 

 Iceland Spar: Merritt (Wied. Ann. 55, 1595) gives tne following values of k in the formula 

 i= i e~ ka (d in cm.) : 

 For the ordinary ray : 



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

 a plate 1 cm. thick: at 0.222/*, 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 /t, becomes opaque, metallic reflection at 8.50/1, 9.02, 20.7 5-24.4/t, then trans- 

 parent again. 



The above are taken from Kayser's " Handbuch der Spectroscopic," vol. Hi. 

 Smithsonian Tables. 



