WHICH NITROGEN IS SUBSTITUTED EOR HYDROGEN. 
723 
The formation of this compound may be expressed by the following equation : — 
€ 12 H 6 N 4 , 2HBr, Br 4 *+ 8NH 3 =€ 12 H 8 N 6 +6NH 4 Br. 
^ V 1 y V 1 
Perbromide. Tetrazodiphenylimide. 
It has been my endeavour to study somewhat more closely the compounds which 
tetrazodiphenyl forms with metallic hydrates, but all my attempts to obtain them more 
definitely have failed, and their preparation seems indeed to be beset with insurmount- 
able difficulties. I omit a lengthened description of the unsuccessful attempts, and will 
merely show by one instance how tetrazodiphenyl can play the part of an acid. An 
aqueous solution of nitrate of tetrazodiphenyl, when mixed with caustic potash, yields a 
yellow liquid exhibiting such properties as might be looked for in absolution of the com- 
pound of hydrate of potassa with tetrazodiphenyl. On treating it with chloride of pla- 
tinum, it gives rise to the formation of the platinum-compound above described, a proof 
that the tetrazodiphenyl remains unchanged in the alkaline solution. It is invariably 
decomposed on the application of heat, with evolution of gas and separation of a reddish- 
brown amorphous substance. 
PRODUCTS OE DECOMPOSITION OE THE COMPOUNDS OF TETRAZODIPHENYL. 
By applying the laws of classification just now accepted by chemists to the tetrazotized 
derivatives of benzidine, specially taking into account their manner of formation and 
combination, these bodies must be classified with the diatomic compounds, whilst the 
respective diazo-compounds belong to the monatomic bodies. It has been of late a 
favourite subject of chemical research to trace the analogies which monatomic bodies 
exhibit under the influence of certain agents with polyatomic bodies. In illustration of 
this I may refer to the results obtained in the comparative study of the products of 
decomposition of the ethyl- and ethylene-alcohols in order to show how simple are the 
laws which regulate these chemical transformations. The experimental results which 
I am able to adduce prove likewise that the decomposition of the tetrazo-compound 
gives rise to derivatives which differ in nothing from those obtained under similar 
circumstances from diazo-compounds, beyond the distinctive features imparted to them 
by the polyatomic nature of the compound from which they are derived. 
Action of Water upon Nitrate of Tetrazodiphenyl. 
An aqueous solution of this body, when left in a cold place, gradually undergoes a 
spontaneous decomposition. When heated it gives rise to a copious evolution of nitrogen 
gas with separation of two substances — one an amorphous brown, and the other a white 
crystalline body. An additional quantity of the latter is obtained when the liquid has 
* Leaving aside the hydrobromic acid, this compound may be looked upon as the bromide of a tetratomic 
radical (G 12 H 6 N 4 ) IV Br 4 . 
MDCCCLXIV. 5 D 
