( 508 ) 
filled with the vapour which was in equilibrium with the liquid the 
two stopcocks were closed. After introducing aqueous sodium hydroxide 
by gently opening one of the stopcocks until all HBr and Br had 
been absorbed, the solution was introduced into a measuring flask 
and diluted to the mark. An aliquot portion was then titrated at 
once with KJ and Na,S,O,, and in another portion the bromine was 
all converted into bromide by means of H,O, and then titrated 
according to VoLHarD with AgNO, and NH,CNS. In this way we 
found the free bromine and the total bromine from which the relation 
HBr: Br, may be calculated. In a similar manner the composition 
of the liquid was determined. At O° we found for the liquid 
8 mol.°/, of HBr and 92°/, of Br,; for the vapour 87 °/, of HBr 
and. 13°), “ofelare2): 
This result renders the existence of a compound in the vapour 
highly improbable, for if a compound occurs in a binary system in 
the fluid phases an inward bend is noticed in the p, 2- or ¢, a-curves; 
the liquid- and the vapour branch approach each other more or less 
according to the degree of dissociation of the compound. Judging 
from our observations there can be no question of something of the 
kind taking place in our case. 
We beg to say just a few words as to the significance of these results 
in connection with the supposition mentioned above. Although we have 
proved that HBr and Br, in a pure state do not form a compound it 
cannot be denied that facts may be disclosed which plead for the existence 
of such compounds in solvents. But those facts only relate to solu- 
tions which possess electrical conductivity power and in which we 
must assume a powerful action of the solvent on the dissolved 
matters: in our case splitting into H’- and Br'-ions. One might cer- 
tainly imagine that the Br'-ion has a tendency to take up Br, and 
to pass into Br'’,-ion without this necessitating the existence of a 
compound HBr,, but in non-conductive solutions the idea of the 
existence of compounds HBr, should, in our opinion, be rejected. 
Amsterdam, December 1908. Inorg. chem. labor. University. 
1) These experiments are being continued. 
