66 



INFRA-RED TRANSMISSION SPECTRA. 



In fig. 53, curve a, is shown the transmission curve or ordinary soft 

 glass which has been blown into a bulb of such a thickness that it 

 showed interference colors. This is the thinnest film yet examined. 

 There is one large complex absorption (reflection) band extending from 

 8.5 to 10.7 p., the maximum being at 9.7 p. 



ALBITE (NaAlSi 8 O 8 ). 

 (/ = o.i4. Curve b, fig. 53-) 



This mineral is more transparent than orthoclase (fig. 51, curve a). 

 The absorption bands at 2.9, 5.7, and 6.3 fi coincide with those of ortho- 

 clase. 



ENSTATITE (MgSiO 8 ). 

 ("Bronzite." t = i mm. Curve c, fig. 53.) 



This specimen was a mixture of several crystals. The transmission 

 curve shows a large absorption band at 1.85^, and smaller depressions 

 at 2.9 and 5.2 p. 



~1 



/ .? 3 ? S 5 89 



FIG. 54. Ebonite (a) ; Rubber. 



EBONITE. 

 (t o.i mm. Curve a, fig. 54.) 



In fig. 54 is shown the transmission curve of ordinary ebonite, which 

 has been ground thin, so that it was subtranslucent. It is quite trans- 

 parent to 14 p., with absorption bands at 3.4, 5.9, 6.9, 8.3, 9.1, and 10 p., 

 which are in coincidence with bands belonging to carbohydrates. 



PARA RUBBER. 

 (Subtranslucent; t = 0.27 mm.) 



In curve b, fig. 54, is given the transmission curve of a thin piece of 

 sheet rubber. It is very opaque, but shows a large band at 3.3 p.. 



STIBNITE (Sb 2 S 3 ). 

 (Cleavage piece parallel to b; = 0.45, 0.98 and 4.9 mm. Fig. 55.) 



This is one of the most remarkable substances examined. It has a 

 metallic luster, which is highly splendent on fresh cleavage surfaces. 



