INFRA-RED TRANSMISSION SPECTRA. 



of the films was about o.i mm., and in the case of lactose the color was 

 slightly tinged, due to decomposition. The water bands are present as 

 noted elsewhere. The region from 3 to 4 p. is complex, with the maxi- 

 mum at 34ft. 



RAFFINOSE (Ci 8 HaO 

 (Amorphous solid melted between rock salt; t = o.2 and 0.05 mm. Fig. 22.) 



This sugar melts very easily and forms perfectly transparent solid 

 films. The transmission curve shows all the water bands, viz, 1.5, 2, 



3, 4.75, and 6.05^. The 

 band at 3 p. is quite dis- 

 tinctly resolved into the sec- 

 ond component lying in the 

 region of 3.3 p. The trans- 

 parent region at n p. is just 

 the reverse of the alcohols, 

 which have an absorption 

 band at 11.3 /*. 



GUM ARABIC (2C 8 H 10 O B +H a O). 

 (f = 0.1805. Fig. 23.) 



Two samples were exam- 

 ined. The first was a film 

 of the gum dissolved in 

 water and placed between 

 two plates of thin micros- 

 cope cover-glass, which was 

 kept over P 2 O 5 for several 

 days. The second was the 

 combination of two films 

 6//, which were spread over 

 cover-glass and dried over 

 P 2 O 5 for several days. The 



cracked and peeled off, so that it was necessary to place two facing 

 other. The water bands are of course visible, while the region at 

 is complex. 



Fio. 23. Gum arable. 



films 

 each 

 3.5 fj. 



RocHlXue SAi,T(CHOKNa+4H a O). 

 (t 1.27 and o.i mm. Fig. 24.) 



Curve a shows the transmission through a transparent crystal section, 

 while curve b is for a solid film melted between two thin plates of 

 cover-glass. In the latter case the film was flaky, which decreased the 



