WHICH NITBOGEN IS SUBSTITUTED EOE HYDEOGEN. 
669 
Another method of preparing nitrate of diazobenzol is based upon the action of nitrous 
acid upon diazo-amidobenzol, a body described in a previous communication to the Royal 
Society. On dissolving this latter compound in cold ether, and passing a current of 
nitrous acid gas through the solution, long acicular crystals of the new substance soon 
appear. The action should be continued as long as crystals form. The compound so 
obtained is collected on a filter and washed with ether. The reaction is expressed by 
the following equation : — 
Diazo-amidobenzol. Nitrate of diazobenzol. 
However elegant and simple this method of preparation of the nitrate of diazobenzol 
may appear, it will scarcely ever be employed, since it involves the previous preparation 
of diazo-amidobenzol, a body which it is rather troublesome to obtain in large quantities. 
Nitrate of diazobenzol can also be procured by the direct action of nitrous acid upon a 
mixture of aniline with about four times its volume of alcohol. The gas is passed into 
the alcoholic solution till, on the addition of ether to a small portion of it, a copious 
precipitation of white acicular crystals is produced. When this point is reached, the 
whole of the reddish-brown solution is mixed with ether, and the precipitate purified as 
already described. 
This method of preparing the nitrate, however, is not suitable when large quan- 
tities have to be prepared. It is similar in principle to the preparation by means of 
diazo-amidobenzol, since to all appearance the aniline is first converted into this com- 
pound. 
The methods just described, although simple, will only give favourable results when 
strict attention is paid to the directions given above ; for it happens sometimes, and 
especially when the temperature of the solution is allowed to rise too high, that a copious 
evolution of nitrogen gas ensues, which cannot be stopped by any means before the whole 
of the substance has been destroyed. 
By employing the first of the above processes, it is sometimes found that, on the addi- 
tion of ether to the weak alcoholic solution of the crude compound, no crystals separate, 
but that an aqueous layer is deposited at the bottom of the vessel. This, however, only 
happens when an insufficient amount of alcohol has been originally added to the solu- 
tion, because in this case the ether, not being able to mix with the liquor, causes no 
separation of crystals to take place. If this occurs, it is best to remove the ethereal 
liquor, and to dilute the residuary aqueous solution with strong alcohol, when, on the 
addition of ether, crystallization invariably ensues. 
The nitrate of diazobenzol, by whatever method it may have been prepared, crystal- 
lizes in long white needles, which have been obtained several inches in length and are 
very soluble in water, less so in alcohol, and almost insoluble in ether and benzol. They 
can be dried over sulphuric acid without undergoing any change. Heated even below 
100° C., they explode with unparalleled violence, far surpassing that of fulminating mer- 
4 u 2 
