176 



Mr. P. Griess on some 



[Feb. 15, 



is acted upon by sodium nitrate, a white crystalline azo-acid immediately 

 separates, and that whether the hydrochloric acid is in excess or not. 

 The azo-acid thus obtained from the (3 diamidobenzoic acid crystallizes 

 in short needles, which are soluble with difficulty in hot water, and 

 scarcely at all in cold. "When heated in a dry state it melts and blackens, 

 a small portion subliming, whilst the greatest part is decomposed, leaving 

 behind a difficultly combustible carbonaceous residue. The composition 

 of this azo-acid corresponds with the formula C 7 EL N 3 2 . Its barium salt 

 has the composition (C 7 H 4 N 3 2 ) 2 , Ba + 4H 2 0, and crystallizes in very 

 slender colourless needles, which dissolve readily in hot water, but only 

 sparingly in cold. 



The azo-acid prepared from the y diamidobenzoic acid, although iso- 

 meric with that just described, differs considerably from it, crystallizing in 

 long hair-like silky needles, which, on drying, shrink together to a felt-like 

 mass. It is rather more easily soluble in hot water than the corresponding 

 a acid, and when gently heated melts to a yellow oil, partial sublimation 

 taking place at the same time ; at a higher temperature it decomposes 

 with slight explosion. Its barium salt crystallizes in white needles, which 

 are rather difficultly soluble in hot water, and very sparingly so in cold. 

 Its composition is expressed by the formula (C 7 H 4 N 3 2 ) 2 , Ba+2H 2 0. 



The formation of these two azo-acids may be thus expressed : — 



C 7 H 8 N 2 2 + NH0 2 = CLILN^ + 2H 2 0. 



/3, I diaWoben- Nitrous ft 1 Water. 



y j zoic acids. acid. y J 



I may add that both these acids contain water of crystallization, which is 

 expelled at 100° C, and at the same time call attention to their great 

 stability, in which respect they differ very remarkably from most other azo- 

 compounds. Finally, I would remark that three other compounds, having 

 the same formula as these azo-acids, are already known, to which I gave 

 the names diazobenzimide, diazodracylimide, and diazosalylimide*. They 

 were obtained by the action of ammonia on the perbromides of the corre- 

 sponding diazo-acids, as shown in the equation — 



C 7 H 4 N 2 2 ,HBr,Br 2 + 4NH 3 = (C 7 H 4 N 2 2 )^ J N + 3N H 4 Br. 



Perbro- f diazobenzoic acid, Ammonia. Diazobenzimide, Anrnomum 



mides \ diazodracylic acid, diazodracylimide, bromide, 



of ... L diazosalylic acid. diazosalylimide. 



These bodies also form saline compounds with metals, but in their re- 

 actions, as well as in other respects, differ entirely from the azo-acids just 

 described, rendering it certain that they have a different constitution from 

 them. 



* Zeits. Chem. 18G7, p. 164. 



