96 PROCEEDINGS OP THE AMERICAN ACADEMY 



added to the hot solution, and the whole hoiled on the steam hath 

 for ahout three hours. As with benzoic acid, the phosphorpent- 

 oxide did not dissolve, but settled to the bottom of the flask as 

 an amorphous, gelatinous mass, which became gradually darker- 

 colored as the heating progressed, until, at the end of the operation, 

 it was almost black. The amber-colored, supernatant liquid was 

 decanted hot through a plaited filter and allowed to crystallize. 

 After standing over night it had thrown down a considerable 

 quantity of large, feather-shaped crystals, which, as their amount 

 did not appear to increase on longer standing, were filtered, and 

 washed with dry benzol. Their melting point, 147°, and ready 

 solubility in alkalies, as well as their characteristic sweet taste, 

 showed them to be the unchanged o-nitrobenzoic acid. 



The mother-liquor from these crystals was concentrated to about 

 one third of its original volume and allowed to stand. The result 

 was a precipitate of short, thick, prismatic crystals, entirely dif- 

 ferent from the feather-shaped forms of the nitro acid, and melting 

 at 128° to 130°. By repeated crystallization from benzol, this 

 melting point was raised to 133°, at which temperature it remained 

 constant. The analyses gave the following results : — 



0.3393 grm. substance gave 25 c.c. nitrogen at 3.2° and 749.8 mm. 

 0.2564 grm. substance gave 0.5016 grm. C0 2 and 0.0700 grm. H 2 0. 



In its properties the substance agrees with those assigned to the 

 anhydride of orthonitrobenzoic acid by Bischoff and Roch,* viz. 

 difficultly soluble in water and ether, more readily in alcohol, ben- 

 zol, and glacial acetic acid. Heated quickly upon platinum foil it 

 explodes. Continued treatment with boiling water or with alka- 

 lies converts it into the acid. Bischoff and Roch place the melt- 

 ing point of the anhydride at 135°, while we have not been able to 

 raise it above 133°. 



* Berichte, XVII. 2789. 



