292 DIAZO-COMPOUNDS. 



paration of diazobenzene ; that used in the experiments was 

 of excellent quality as regards purity. 



3. Diazobenzene nitrate was prepared by the well-known 

 (Griess's) process of treating aniline nitrate with nitrous acid. 

 Five to 6 grms. of pure aniline nitrate were taken. This was 

 pounded and mixed with a little water, so as to form a paste, 

 which was placed in a tube surrounded with a refrigerating mix- 

 ture. A current of nitrous acid was then slowly introduced into 

 it, the mixture being continually stirred, so as to carefully avoid 

 any heating. The liquid at first turns a deep red, but afterwards 

 assumes a lighter tint. As soon as it begins to give off nitrogen 

 the operation is stopped. We then add to the liquid its own 

 volume of alcohol, and subsequently an excess of ether, which 

 precipitates diazobenzene nitrate. The latter is washed upon a 

 cloth with pure ether; it is then pressed and dried in vacuo. 

 In this way 67 per cent, of the theoretical yield was obtained. 



4. Stability. Diazobenzene nitrate placed in a dry atmo- 

 sphere, and protected from the light, has been preserved for two 

 months and longer, without alteration, When exposed to day- 

 light, it becomes pink, and then changes more and more, 

 although slowly. 



This alteration is much more marked under the influence of 

 moisture; the compound first emits an odour of phenol, and 

 assumes a peculiar tint ; then, after a time, it expands, becoming 

 black and giving off gases. Merely breathing upon this com- 

 pound will cause it to turn red. 



On contact with water, it is immediately destroyed, giving off 

 nitrogen, phenol, and various other products 



C 6 H 5 N 2 N0 3 + H 2 = C 6 H 6 + N 2 + HN0 3 . 



Diazobenzene nitrate is quite as sensitive to a shock as mercuric 

 fulminate; when struck by a hammer, or rubbed rather 

 vigorously, it detonates. It is much more susceptible to the 

 influence of moisture and light than the fulminate. 



5. When heated beyond 90, diazobenzene nitrate detonates 

 with extreme violence. Below this temperature it decomposes 

 gradually and without detonation ; at least, when it is heated 

 in small quantities. We see by this that diazobenzene nitrate 

 is much more sensitive to heat than mercuric fulminate a 

 compound whose point of deflagration under the same conditions 

 is about 195. 



6. Density. The density of diazobenzene nitrate has been 

 found to be equal to 1/37, by means of the volumenometer, 

 or one-third that of the fulminate. A high pressure slowly 

 brought to bear on this body brings it to an apparent density 

 approximating to unity. 



7. Composition. 0*5 grm. burnt by detonation in an atmo- 

 sphere of pure oxygen, gave the theoretical proportion of 



