TABLE 549.— INDEX OF REFRACTION OF MISCELLANEOUS 

 BIAXIAL CRYSTALS 



529 



Index of refraction 



Spectrum 



Crystal line 



Ammonium oxalate, (NH 4 ) 2 C 2 4 -H 2 D 



Ammonium acid tartrate, 



(NH«)H(C«H«0.) D 



Ammonium tartrate, (NH 4 ) 2 C 4 H 4 O e D 



Antipyrin, CuHi 2 N0 2 D 



Citric acid, CeHsCvH.O D 



Codein, C 18 H 21 NCvH 2 D 



Magnesium carbonate, MgC(V3H 2 D 



sulfate, MgS0 4 • 7H 2 D 



Cd, .226^ 



H, .656^ 



Potassium bichromate, K 2 Cr 2 0v D 



chromate, K 2 Cr0 4 D 



red 



nitrate, KN0 3 D 



sulfate, K 2 S0 4 F 



D 



" C 



Racemic acid, C 4 H e CvH 2 yellow 



Resorcin, C«H 8 C)2 D 



Sodium bichromate, Na 2 Cr 2 CV2H 2 D 



acid tartrate, NaH(C 4 H 4 O fl )-2H 2 0.. red 



Sugar (cane), G 2 H 22 0n Tl 



" D 



" Li 



Tartaric acid, C 4 H 6 O a (right-) D 



Zinc sulfate, ZnS0 4 -7H 2 F 



D 



" C 



1.4381 



1.5475 



1.5950 



TABLE 550.— SPECIFIC GRAVITY, COEFFICIENT OF EXPANSION, AND STAIN 



CLASS OF OPTICAL GLASS * 



Specific gravity 



Cofficient of expansion 

 mean values X 10 7 



Glass type 



BL 



CG 



40° to C 

 BL 



73.0 

 62.0 

 75.8 

 70.2 

 74.2 



76.2 



57.8 

 60.8 

 70.8 



0° to 40° 

 BL 



77.0 

 65.2 

 80.2 

 73.0 

 78.0 



80.6 



61.2 



64.0 

 73.0 



0° to 100° 

 BL 



79.6 



67.5 

 83.0 

 74.5 

 80.0 



81.9 



64. i 



66.9 

 74.2 



0° to 300° 

 CG 



80 



99 



86 

 70 

 71 



89 

 72 

 87 

 85 



Stain 

 class 

 for 

 BL 



511635 2.48 



517645 2.53 2.53 



523586 2.53 



529516 2.73 



573574 3.21 



580410 3.27 3.21 



584460 3.31 



605381 3.49 3.47 



611572 3.57 3.56 



611588 3.58 3.40 



617366 3.64 3.58 



617550 3.66 3.50 ... ... ... 72 5 



620362 3.67 3.61 ... ... ... 87 1 



649338 3.91 3.89 ... ... ... 85 2 



720293 4.51 ... 73.5 75.2 77.3 .. 3 



Melt No. 



EK-1 10-5328 4.1 



EK-32-2641 ' 4.5 



EK-33-2734s *" 4.7 



EK-45-29 4.6 



BL, Bausch & Lomb Optical glass. EK, Eastman Kodak glass. CG, Corning glass. 

 The first IS glass types in column 1 are described in Table 524 of NBS glasses. 



Types of glass in class 1 or 2 are not likely to stain even when used as exposed surfaces in tropical climates. 

 Glasses in class 5 are liable to stain when exposed to rain, moisture condensation, or fingerprints in any climate. 

 Other glasses are intermediate in stain resistance. 



SMITHSONIAN PHYSICAL TABLES 



