WHICH NITROGEN IS SUBSTITUTED EOE HYDROGEN. 
675 
gave, on precipitation with sulphuretted hydrogen and ignition of the tersulphide of 
gold, 0-309 grin, of gold, corresponding to 44-36 per cent, of that metal. 
C 6 H 4 N 2 ,HC1, Au Cl 3 . 
Theory. Experiment. 
Gold .... 44-37 44-36 
It is well known that when bromine, chlorine, or hyponitric acid is substituted in 
organic compounds for certain hydrogen atoms, the product formed is distinguished from 
the original compound, if the latter be an acid, by stronger acid properties, or if a base, 
by less pronounced basic characters ; and also that the contrary is observed in the case 
of substitution of potassium, NH 2 , &c. for the same hydrogen atoms. 
Nitrogen, however, exhibits in this respect a peculiar double nature, since it is found 
only slightly (or not at all) to affect the basic properties of a compound, whilst at the 
same time it exerts so decided an acidulating action as to impart to strong bases an acid 
nature. I have already clearly shown that diazobenzol has all the characters of an 
organic base, capable, like aniline, of forming with acids saline compounds. It possesses, 
at the same time, the property of combining with metallic hydrates, playing, to a certain 
extent, the part of an acid. These metallic derivatives are, as a rule, distinguished by 
the same instability as the compounds of diazobenzol with acids. They are less affected, 
however, by heat. Their aqueous or alcoholic solutions can be heated to boiling for 
some time without suffering complete decomposition. Heated alone they explode, 
although at a much higher temperature, and not with so great violence as the bodies 
previously described. The compounds which are soluble in water are mostly well 
crystallized, whilst the insoluble ones, such as those formed with silver and lead, are 
obtained as amorphous precipitates. 
Compound of Hydrate of Potassium with Diazobenzol, G 6 H 4 N 2 , KHO. 
By introducing a very concentrated solution of nitrate of diazobenzol into an excess 
of an equally concentrated solution of caustic potash, drop by drop, a yellowish liquid 
is obtained possessing a peculiar aromatic odour, and solidifying, by evaporation in the 
water-bath, to a crystalline mass. This is a mixture of the compound of hydrate of 
potassium with diazobenzol and nitre, together with a brownish-red amorphous body — 
the result of a secondary reaction, which a portion of the original substance undergoes, 
and which is always indicated by the evolution of gas. In order to separate these bodies 
it is necessary to remove the excess of caustic potash. This is best done by putting the 
crystalline mass into a strong linen cloth and squeezing it powerfully between porous 
stones. The dry cake is then treated with absolute alcohol, which readily dissolves the 
compound of hydrate of potassium with diazobenzol, leaving the nitrate of potassium 
insoluble ; it is then separated by filtration. The alcoholic filtrate (which, on account 
mdccclxiv. 4 x 
