80%r 



30 INFRA-RED TRANSMISSION SPECTRA. 



Curve f, fig. 2oa, is for an amorphous film of beet sugar, which also 

 shows the 1.5 /x, band. Curves e and h are for two large, clear crystals 

 of rock candy, respectively 2 and 1.7 mm. in thickness, in which the 1.5/1, 

 band is unusually strong, which would indicate that there was no decom- 

 position in melting the other films. An analysis by Dr. J. C. Blake 

 showed that the rock candy contained 99.81 per cent pure sugar, while 

 the water content was about 0.05 per cent. Now, it has never before 

 been suspected that cane sugar has water of crystallization, and the 

 present disagreement with the results of chemists who have made a 



life-long study of sugars in 

 general must be considered 

 with caution. A compari- 

 son with lactose, maltose, 

 and dextrose would indicate 

 the presence of a molecule 

 of water of crystallization. 

 There may be other ex- 

 planations for this excep- 

 tion. It has already been 

 noted that the sugars are 

 rich in OH groups, which 

 will confuse matters at 3 /x. 

 where the OH radical has a 

 characteristic band, so that 

 the effect of water must be 

 based upon the small bands 

 at 1.5 and 4.75 /x. In the 

 present work on mannite 

 (C 6 H 8 (OH) 6 ) and in pre- 

 vious work 1 on ethyl alcohol 

 (C 2 H 5 OH) and myricyl alcohol (C 30 H 61 OH), as well as on glycerin 

 and on phenols, there is no indication of absorption bands at 1.5, 2, 

 4.75, and 6/x,, so that their presence in the cane-sugar spectrum can 

 hardly be attributed to the OH group. In Puccianti's curves 2 the alco- 

 hols show depressions at i-5/x,, but they are not very sharp, although 

 he used a larger dispersion and a thicker cell. As a whole, the question 

 is in an unsettled state with the results obtained by the method of 

 absorption spectra indicating the presence of a molecule of water of 

 crystallization in cane sugar which has heretofore been considered to be 

 composed entirely of water of constitution. 



FIG. 2oa. Cane sugar. 



1 Investigations of Infra-red spectra, Washington, 1905. 

 3 Puccianti : Nuovo Cimcnto, II, p. 241, 1900. 



