IX, A, 2 



Pratt and Brill: Phthalide Compounds 



107 



The glacial acetic acid solution was colorless, and gave a 



well-marked absorption band heading at - 



A 



3340 and show- 



ing considerable persistence. The anhydride in concentrated 

 sulphuric acid gives a similar band heading nearer the red 



at = 3130 and appearing at somewhat lower concentration. 



11 

 Two new bands heading at ^ = 3860 and - = 4200 also show, 



A A 



the former being shallow and the latter well defined. General 

 absorption more nearly approaches the visible region (fig. 1). 



Oscillation frequency. 

 2S 23 3000 32 3-f 36 38 4000 4-Z 44 



46 



^4 



3.2 



3.0 



2.8 



2.6 



2.4 



22 



2.0 



18 



^- 1.6 



E 



o 



2. /. 



\ I 



I I f i \ \ 



1.4 

 1.2 

 1.0 



Fig. 1. Curve 1. Thiophthalic anhydride in glacial acetic acid. Curve 2. Thiophthalic anhydride 



in sulphuric acid. 



