106 The Philippine Journal of Science im 



results upon the spectra. The theory was advanced that such 

 energy was supplied through the medium of conjugation between 

 the solute and the sulphur atom of the acid, resulting, under 

 certain favorable instances, in a conjugated ring characterized . 

 by selective absorption and the production of color. Several 

 such cases were discussed, among which may be mentioned 

 phthalophenone and its anihde. It was also pointed out that 

 the substitution of thionyl for carbonyl in compounds of this 

 type results in a very marked increase of activity. It has 

 long been known that many such sulphur compounds are colored, 

 generally a brilliant red, and this has been explained by attribut- 

 ing greater chromophoric power to thionyl than to carbonyl. 

 Certain known compounds of this type and several new thio 

 derivatives of phthalide have been prepared and their absorption 

 spectra obtained. 



DESCRIPTION OF THE ABSORPTION SPECTRA 



The spectra were photographed in the usual manner, using 

 an iron-nickel arc and Cramer's spectrum plates where neces- 

 sary. The curves are plotted as in the previous paper. Absolute 

 alcohol, glacial acetic acid, and concentrated sulphuric acid were 

 used as solvents. 



THIOPHTHALIC ANHYDRIDE 



c=o 



C6H4<^^S 



c-=o 



Thiophthalic anhydride was prepared from phthalic anhydride 

 and sodium sulphide according to the excellent method of Reissert 

 and Holle.2 The product was repeatedly recrystallized from 

 alcohol and obtained as colorless needles melting at 114° 

 (corrected). 



Analysis of thiophthalic anhydride* 



Substance. '^' 



>riura sul- 

 phate. 



Sulphur. 



Gram. 



Gram. 



Per cent. 



0.2255 



0.3355 



20.44 



Calculated for 



C8H,0.S 



19.54 



'Ber. d. deutsch. chem. Ges. (1911), 44, 3029. 



' Due to the rapid deterioration of hard glass in the tropics, Carius 

 determinations are very difficult to carry out satisfactorily. This fact 

 should be borne in mind in reference to the sulphur analyses here pre- 

 sented. 



