62 



INFRA-RED TRANSMISSION SPECTRA. 



MALIC ACID (C 2 H 3 (OH) (CO 2 H) a ). 

 (f = o.o8. Curve b, fig. 48.) 



This compound belongs to the trivalent dibasic acids (C n H 2n _,,O 6 ), 

 and, like the acids previously studied, is very opaque, with wide absorp- 

 tion bands at 3.5, 5.9, and 7.2 p.. 



SODIUM BIBORATE (Na 2 Br 4 Oi). 

 (Fused glass, transparent, ground to t = o.i2 mm. Curve a, fig. 49.) 



This compound is formed on fusing borax (Na 7 B 4 O 7 ), which con- 

 tains 10 molecules of crystal-water. It is difficult to decide whether or 

 not the bands at 3 and 4.8 p. are due to H 2 O. There are other bands at 

 1.9 and 3.7/1. 



90% 



80 



70 



60 



' 50 



V) 



(0 



h 



30 



20 



IO 



IO to 14- u 



3 3 * -5 6 7 8 



FIG. 49- Sodium biborate (a) ; Silver nitrate. 



SILVER NITRATE (AgNOa). 

 ( = 1.65 mm. Curve b, fig. 49.) 



This crystal was ground, but not highly polished. Its transmission 

 curve is marked for its sharp bands at 2.7, 3.6, 4.1, 4.78, and 5.65 /x. 



