OF ARTS AND SCIENCES. 163 



For analysis the substance was crystallized from aloohul and dried 

 at 100°. 



I. 0.2673 grm. substance gave 0.7341 grm. CO., and 0.1279 grm. 



11,0. 



II. 0.2432 grm. substance gave 0.6690 grm. CO.^ and 0.1141 grm. 



H,0. 



Calculated for CieH,jOs. Found. Apjohn and Gregory. 



C 75.00 74.91 75.01 74.27 



H 5.00 5.31 5.25 5.61 



Since the substance was very refractory and needed a high tempera- 

 ture in a stream of oxygen for complete combustion, my results show 

 a sufficiently close agreement with those of Apjohn and Gregory. 



This substance melts at 162° and volatilizes with partial decompo- 

 sition at a higher temperature, although it may be sublimed without 

 difficulty by careful heating in a current of air. In concentrated sul- 

 phuric acid it dissolves with an intense purple, and in hydrochloric or 

 hydrobromic acid with a crimson color. From these solutions water 

 precipitates the substance apparently unchanged. In alkaline solutions 

 it is completely insoluble, and by melting caustic potash it is merely 

 carbonized. Bromine attacks it vigorously, and, under certain condi- 

 tions, forms well-crystallized products. 



Dibrompyroxanthintetrabromide^ C^HjoBrgOgBr^. When pyroxan- 

 thin is suspended in ten times its weight of carbonic disulphide, and 

 three and a half parts of bromide diluted with an equal weight of car- 

 bonic disulphide are added, the pyroxanthin instantly dissolves and 

 forms a clear deep-red solution. After standing for a short time, clouds 

 of hydrobromic acid are given off, and soon after the separation of a 

 beautifully crystalline substance begins. After twenty-four hours the 

 carbonic disulphide is poured off, and the crystals which have separated 

 are thoroughly washed with ether. For analysis I recrystallized the 

 substance from boiling chloroform and dried it in vacuo. 



I. 0.5598 grm. substance gave 0.5136 grm. COg and 0.0842 grm. 

 H,0. 



II. 0.6814 grm. substance gave 0.5758 grm. COj and 0.0845 grm. 



R,0. 



III. 0.3094 grm. substance gave 0.4884 grm. AgBr.* 



IV. 0.3128 grm. substance gave 0.4936 grm. AgBr. 



* All the determinations of halogens in this and the subsequent investiga- 

 tions were made according to the method of Carius. In most cases the asbestos 



