WATER OF CRYSTALLIZATION. 



39 



transparency. The crystal section was examined with difficulty because 

 of its low melting-point. Curve c shows the band at 4.75 yu, magnified 

 10 times. The water bands at 1.5, 2, and 4.75 //, are very apparent, while 

 the one at 3 /* is obliterated, as with the sugars. 



BRUCINB (C 28 H2eN a 

 (Thickness: = 0.05; b=i.i$ mm; c = o.i5 mm. Fig. 25.) 



Brucine belongs to the alkaloids, which have a complicated and 

 unknown structure. As will be noticed from the curves it is very 



50 



40 



C. 



o 

 'w 



30 



c 



<D 



20 



10 



a 



0/2345 



FIG. 24. Rochelle salt. 



transparent to contain 4 molecules of crystal water. The 6 p. band is 

 the only one that is conspicuous, while the strong one at 3 p. is entirely 

 absent. The water is easily expelled at a low temperature. Curve b 

 is for a thick layer of amorphous material melted on a plate of rock 

 salt. It shows the general carbohydrate band at 1.7^, and the 3.43 /i 

 band characteristic of compounds rich in CH 2 or CH 3 groups. For 

 curve a the film was made by placing the solid powder between two 

 plates of rock salt, which were heated on a metal plate, and as soon as 



