OF ARTS AND SCIENCES. 167 



I found, however, tliat the substance turned brown on standing over 

 sulphuric acid, and tJie analysis of two diflerent preparations showed 

 conclusively that no constant results could be obtained in this way. 



I. 0.3726 grm. substance gave 0.3142 grm. COg and 0.0594 grm. 



11,0. 

 IT. 0.2016 grm. of the same preparation gave 0.2773 grm. AgBr. 



III. 0.5255 grm. substance gave 0.4142 grm. COj and 0.0734 grm. 



H,0. 



IV. 0.3853 grm. of the same preparation gave 0.5731 grm. AgBr. 



I. n. ni. IV. 



C 23.00 21.50 



H 1.77 1.55 



Br 58.53 63.30 



These results showed merely that oxidation had taken place together 

 with the substitution .of hydrogen by bromine. 



On boiling with bromine-water, total decomposition seemed to en- 

 sue, and no definite products could be isolated except oxalic acid and 

 a small quantity of a volatile oil which had the odor of bromoform, 

 and gave the characteristic odor of phenyl isocyanide when heated 

 with anilin and alcoholic potash. 



Although I have already carried on the investigation of pyroxan- 

 thin in several other directions, I have not as yet been able to study 

 the reactions involved as much in detail as I could wish, and I must 

 therefore reserve for a subsequent paper all description of these ex- 

 periments. 



Concerning the origin and mode of formation of the pyroxanthin, I 

 can at present add nothing. Its high melting point, and its general 

 behavior when compared with the properties of the oil from which it 

 is made, lead directly to the conclusion that it results either from 

 polymerization or condensation. Its formula, Cj^Hj^Og, naturally sug- 

 gests a trimolecular polymeric form ; the composition of its bromine 

 derivatives, on the other hand, favors rather the view that its mole- 

 cule is the product of condensation. 



Schweizer,* in 1848, prepared from pyroligneous acid an oil to 

 which he gave the name pyroxanthogen, as the substance from which 

 the pyroxanthin was formed. He attempted no explanation of the 

 mode of formation, and made no analysis of his product. Although 



* Jour, pract. Chem., xliv. 129. 



