Chemustry and Physics. 305 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHYSICS. ‘ 
1. On the Reciprocal Displacement of the Halogens.—The ready 
t of bromine by chlorine is a well-known fact. It 
ct 
. 
I 
the simultaneous production of the inverse reaction, BERTHELOT 
n | mine more 
and of dissociation of which explain the phenomena obse ved. 
Thus his experiments showed that KCI, acted on ne equiva- 
lent of pure bromine, produced no appreciable effect either cold 
and nine distillations, 7°8 per cent was displaced. 
i bromine, after four hours 
of heating to redness and eight distillations, e 
decomposed ith AgCl, with two equivatents f Br in the cold 
py . With seven equivalents, 
e 
; p 
in the cold five days, 7-2 per cent. With 
at a red heat for three hours, six distillations, 97 per cent. 
bromine chloride is a product common to all 
=KBr, +BrCl: —4:6+46+109= + 
'.=BaBr, + (BrCl), : —13°6 +92 + 20°8= + 
the chlorobromide of barium evolves heat as follows : 
4+3°0 ealories. It therefore assists 10 the same 
. cal reactions the action 1s at first 
prompt, but becomes more and more slow as it goes OD. 
author attributes this to the formation of certain double salts and 
Secondary compounds, the heat of combination of which exceeds 
the heat called into play in the direct decomposition of the simple 
Am. Jour. Sc1.—Turrp Serres, Vou. XXV, No. 148.—APRIL, 1883. 
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