704 
MR. P. G-RIESS ON A NEW SERIES OE BODIES IN 
The properties of the dibromobenzol prepared in the manner just described can 
leave no doubt that it is identical with the dibromobenzol described by Couper, obtained 
by the action of bromine upon benzol. Although large quantities of dibromobenzol can 
be prepared by Couper’s method with perhaps greater facility, it is always difficult to 
obtain the dibromo- quite free from tribromo-benzol, which is simultaneously formed. 
The above method might be preferred in all cases when absolutely pure dibromo- 
benzol is required, as, for instance, for certain physical purposes — the more so, since it 
invariably yields theoretical quantities. The same may be said of several other deriva- 
tives of benzol and its homologues, which are obtained from diazo-compounds to be 
described hereafter. 
DIAZODIBROMOBENZOL COMPOUNDS. 
Nitrate of Diazodibromobenzol, G 6 H 2 Br 2 N 2 , NH0 3 . 
This compound is readily obtained by the action of a rapid current of nitrous acid . 
upon an aqueous solution of nitrate of bromaniline containing free nitric acid. The 
liquid is allowed to evaporate spontaneously, the residue taken up with weak alcohol, 
and the new compound precipitated by means of ether. It can be recrystallized with- 
out loss from water or alcohol by evaporating the respective solutions below their boil- 
ing-points. Its aqueous solution remains remarkably constant. Continued boiling even 
for hours frequently leaves some of the substance undecomposed. 
Nitrate of diazodibromobenzol crystallizes in fine white prisms, or elongated hexa- 
gonal plates. It does not detonate with the same violence as the corresponding bodies 
previously described. 
Perbromide of Diazodibromobenzol, 0 6 H 2 Br 2 N 2 , HBr 3 . 
This compound is formed by the addition of bromine-water to an aqueous solution of 
the nitrate of diazodibromobenzol, when it is precipitated in the form of fine long needles. 
On boiling with alcohol, and the subsequent addition of water, an oily substance is 
thrown down which soon solidifies, and can be obtained perfectly pure by pressing the 
precipitate between bibulous paper, then distilling, and finally crystallizing from alcohol. 
Thus purified it presents itself in the form of fine long silky needles. This substance 
is evidently tribromobenzol, presenting all the properties of that compound obtained 
by the distillation of G 6 H 6 Br 6 with alkalies by Lassaigne*. 
Platinum-salt of the Hydrochlorate of Diazodibromobenzol , C 6 H 2 Br 2 N 2 , HC1, Pt Cl 2 . 
It separates in small orange oval plates, which are difficultly soluble in water, on adding 
dichloride of platinum to the hydrochlora.te. 
0*722 grm. gave 0*154 grm. of platinum. 
G 6 H 2 Br 2 N 2 , HC1, PtCl 2 . 
Calculated. Found. 
Platinum . . . 21*08 per cent. 21*33 
* Rev. Scient. vol. v. p. 360. 
