WHICH NITROGEN IS SUBSTITUTED FOR HYDROGEN. 
703 
These numbers lead to the formula 0 6 H 4 Br Cl. 
Calculated. 
( ' 
€ 6 
72 
37-60 
H 4 
4 
2-09 
Br 
80 
41-77 
Cl 
35-5 
18-54 
191-5 
100-00 
Found. 
37-52 
2-10 
Chlorobromobenzol is rather difficultly soluble in alcohol, readily so in ether, and 
crystallizes in white needles or plates from a hot saturated alcoholic solution on cooling, 
or by evaporation of the ethereal solution. The crystals possess a peculiar odour, 
resembling that of benzol. 
The double salt of dibromide of platinum and hydrobromate of diazobromobenzol is 
obtained in the form of ruby-red crystals, by mixing a tolerably concentrated aqueous 
solution of the diazo-salt with dibromide of platinum. This compound shows, as might 
be expected, a similar deportment. Like the previous platinum-salt, it breaks up 
according to the equation 
C 6 H 3 Br N 2 HBr, Pt Br 2 =C 6 H 4 Br 2 +Br 2 +N 2 +Pt. 
Platinum-salt of the hydro- Dibromo- 
bromate of diazobromobenzol. benzol. 
Dibromobenzol is readily prepared also from the perbromide of diazobromobenzol 
by heating the latter alone *, or with carbonate of sodium, when it is decomposed 
according to the equation 
G 6 H 3 Br N 2 HBr 3 =G 6 H 4 Br 2 +Br 2 +N 2 . 
Perbromide of diazo- Dibromobenzol. 
bromobenzol. 
A still more convenient method of preparing dibromobenzol consists in the decom- 
position of the perbromide with alcohol, which is completed after a few minutes’ boiling ; 
and if too much alcohol has not been employed, a large portion of the dibromobenzol 
separates at once in the form of crystals. The remaining portion is precipitated on the 
addition of water, in the form of a thick oil, which soon solidifies to a crystalline mass. 
After washing with a little alcohol and pressing between bibulous paper, this mass, 
together with the crystals first precipitated, is subjected to distillation. Dibromobenzol 
distils over as an almost colourless oil, which speedily solidifies. 
Dibromobenzol resembles very much chlorobromobenzol in its various physical pro- 
perties. It crystallizes from ether in the form of rectangular prisms or small plates, 
which are frequently very regular and well formed, sometimes, however, agglomerated 
in various ways. It fuses at 89° C. 
* Only small quantities must be employed, in order to prevent violent explosions. By heating the perbro- 
mide in a long-necked flask the dibromobenzol condenses in the cold part of the vessel. 
