WATER OF CRYSTALLIZATION. 

 d-FRUCTOSE 



33 



(f = o.i mm. Fig. 18.) 



The sugars are complex carbohydrates, the constitution of which is 

 not well known. They are rich in hydroxyl groups similar to the 

 alcohols, and hence one would expect to find a band at 3 /*. We would 

 also expect a band at 3.43 /* due to CH 2 or CH 3 groups, so that as a 

 whole the curve will be complex at 3^. The water bands at 1.5, 2, 



80% 



345 



FIG. 18. rf-Fructose. 



and 4.5 /x, should appear in those compounds containing water of crys- 

 tallization. The region from 4 to 6/x ought to be one of great trans- 

 parency if previous results hold. It is a property of sugars that they 

 decompose and give off water when heated above the melting-point. 



In rf-fructose (C 6 H 12 O G ) the constitutional formula is written 

 CH 2 OH(CHOH) 3 COCH 2 OH. The curve (fig. 18) shows no absorp- 

 tion in the region of the water bands. There is a large band at 3.25 //, 

 and a small one at 5.85, while beyond 7/x, there is complete opacity. 



3 c 



