WATER OF CRYSTALLIZATION. 



35 



CANE SUGAR (C u HOu). 

 (Melted between rock salt; t = o.i. Figs. 20 and 200.) 



In fig. 20 are given a series of curves for different samples of cane 

 sugar, which is supposed not to contain water of crystallization. It is 

 one of the most conspicuous exceptions to the rule, if it really be anhy- 

 drous. Curve a represents the transmission for barley sugar, which is 

 the name given to cane sugar after it has been melted, when it becomes 

 an amorphous mass. Curve b is another sample, partially dehydrated 

 and decomposed, called "caramel." It was light brown. Curve c is for 



90% 



60 



70 



60 



<n 

 ,5 



1*0 

 <0 



u 



30 



to 



a 



d 





to /4 u, 



FIG. 20. Cane sugar. 



a dark-brown caramel made by driving off some 15 per cent of the 

 water. In this sample it will be noticed that the 1.5 and 4.75 p, water 

 bands have quite disappeared, which is to be expected. 



Curve d shows the transmission through a film ( = 0.2 mm.) of 

 chemically pure sugar. It was an amorphous solid melted between 

 two plates of rock salt. It was originally crystallized from alcohol and, 

 hence, was free from water. The amorphous film was colorless, showing 

 that there was no decomposition in melting. Nevertheless the water 

 bands at 1.5, 2 and 4.75^ are present. 



