4 

 Fig. i 



5 6 7 8 



Smithsonite (a); Cerussite. 



10/t 



CHAPTER II. 



INFRA-RED REFLECTION SPECTRA OF VARIOUS SUBSTANCES. 



CARBONATES. 



Smithsonite (ZnC0 3 ). 

 (Stalactitic crystalline mass. From New Jersey. Curve a, fig. i.) 



The specimen examined was highly polished. The reflection curve is 



strong, and is a complex of two 

 bands, as will be noticed in 

 nearly all the carbonates exam- 

 ined. The maxima occur at 

 6.65 and 7.05 //. 



There seems to be a silicate 

 calamine (H 2 0-2ZnOSi0 2 ) hav- 

 ing the same name. In fact 

 the sample was purchased as a 

 silicate. The present examina- 

 tion shows that the specimen ex- 

 amined is the carbonate known 

 by that name. In other words, this is an independent method of analyzing 



such a mineral. 



Cerussite (PbC0 3 ). 

 (From New South Wales. Curve b, figs. 1 and 2.) 



This is a rare mineral and the present specimen was a fragment having 

 a surface about 1.5 by 2 cm. 

 The surface itself was cor- 

 rugated, with several plain 

 highly polished plates about 

 2 by 15 mm. It was the 

 only specimen obtainable 

 and no risk was taken in 

 attempting to grind it. The 

 reflection curve b, fig. 1, 

 therefore does not indicate 

 the true reflecting power. 

 The individual bands, how- 

 ever, are well resolved, the 

 maxima being at 6.9 and 

 7.25 p.. In fig. 2, curve c, the reflection curve is drawn on a larger scale, 

 which emphasizes these maxima. 

 10 



15% 



8 9 10/M 



Fig. a. Strontianite (a); Witherite (b)\ Cerussite. 



