170 



Mr. P. Griess on some 



[Feb. 15, 



of which have the formula C 8 H 6 N 4 7 , so that they may be regarded 

 as isomeric dirritrouramidobenzoic acids, C 8 H 6 N 4 7 = C 8 H ti (N0 2 ) 2 3 . 

 Although I have not yet been able to completely separate these acids from one 

 another, owing to the great similarity of their properties, the following 

 facts leave no doubt as to the correctness of this view regarding their 

 nature. 



Decomposition of the Isomeric Dinitr our amid obenzoic Acids by boiling 

 with Aqueous Ammonia. 



"When the solution of the three isomeric dinitro-acids in aqueous am- 

 monia is boiled for some time, decomposition ensues, resulting in the for- 

 mation of three new isomeric acids of the formula C 8 H 7 N 3 5 , as repre- 

 sented in the following equation : — 



C 8 H 6 N 4 7 + H 2 = C 8 H 7 N 3 5 + NH0 3 . 



Isomeric dini- New isomeric Nitric 



tro-acids. acids, acid. 



From a consideration of the composition of these new acids, it will be evi- 

 dent that they may be regarded as mononitrouramidobenzoic acids, which 

 view is, moreover, confirmed by their chemical reactions. By taking ad- 

 vantage of the difference in the solubility of their respective barium salts, 

 they may be separated from one another. The following are the details 

 of their preparation : — The dilute ammoniacal solution of the mixed dini- 

 trouramidobenzoic acids is kept boiling for about an hour, when the 

 decomposition may be regarded as complete. A sufficient quantity of ba- 

 rium chloride is then added to the hot solution, and on cooling a consider- 

 able amount of needle-shaped crystals separate, which consist of the barium 

 salt of one of the new acids, the /3 nitrouramidobenzoic acid. When the 

 mother-liquor separated from these crystals is sufficiently concentrated by 

 evaporation, another barium salt begins to separate, the quantity of which 

 may be considerably increased by allowing the solution to stand for some 

 hours. The yellowish- white salt thus obtained appears amorphous to the 

 unassisted eye, but on careful inspection will be seen to consist of minute 

 needles. The acid corresponding to this salt I propose to call a nitroura- 

 midobenzoic acid. 



In order to obtain the barium salt of the third nitro-acid, the y nitro- 

 uramidobenzoic acid, the mother-liquor from the previous salt is evaporated 

 nearly to dryness on the water-bath, and the resulting mass washed with 

 cold water *. The residue, when crystallized from hot water, taking care 

 to avoid too long boiling, yields the pure barium salt of y nitrouramido- 

 benzoic acid in bright yellow scales. 



As regards the separation of the three nitro-acids in question from their 



* The washing contains, besides ammonium and barium chlorides, another barium 

 salt, crystallizing ir yellowish-red needles, which I shall revert to in another part of 

 the paper. 



