162 



PEOCEEDINGS OP THE AMERICAN ACADEMY 



cold alcohol, they are recrystallized from boiling alcohol until the 

 substance has a bright, clear, orange-yellow color. Boiling the alco- 

 holic solution with bone-black facilitates the removal of the red 

 impurities. 



Pyroxanthin is completely insoluble in water, and very sparingly 

 soluble in ether or carbonic disulphide ; in hot alcohol, benzol, or 

 glacial acetic acid it dissolves abundantly, and crystallizes in well- 

 developed forms on cooling. From alcohol it crystallizes in small, 

 brilliant, orange-yellow needles with a blue reflex ; from benzol in 

 tolerably large reddish-yellow monoclinic prisms ; and from glacial 

 acetic acids in flat radiated needles, which are formed by the develop- 

 ment of the prism in the direction of the orthodiagonal. The crystal- 

 lographic examination which I made of the substance gave the 

 following results. 



ClLYSTALilNE FOJiil OF PtEOXANTHIN. 



ooi Z 



Monoclinic System. 

 Forms observed {001} ^TOl} |100| plO}. 



a: ^:c=: 2.748 : 1 : 1.413 ac = 87° 56' 



Angles between Normals. 



Found. 



110 :T10 40° 1' 



TOl : 001 26° 46' 



TOl :T00 61" 10' 



TlO : TOO 69° 54' 



TlO : TOl 80° 25' 



Calcalat*d. 



Fundamental angles. 



69° 59' 

 80° 30' 



