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SELECTED ARTICLES. 
not at their maximum of elasticity, the space which the vapors 
of the two mixed liquids occupy is the same as that which 
the vapor of each liquid would occupy separately. But if we 
introduce into a barometer tube two liquids which do not 
mix, the tension of their vapors at each temperature is equal 
to the sum of the tensions of the vapors of the two liquids. 
This difference, which presents the manner in which li- 
quids which mix together and those which do not, behave, 
cannot depend upon the idea that those which mix form only 
a single liquid, the vapor of which possesses its own elasticity. 
For we cannot then comprehend why the vapors of the new 
liquid should not have the same composition as the liquid it- 
self; but the products of distillation show the contrary. I 
believe, that which happens in the liquids which mix is 
owing to a reciprocal attraction between the particles of 
the two liquids which have this property, by virtue of 
which one of the liquids in the liquid state attracts the parti- 
cles of the other, even when the other is in the gaseous state. 
By this, then, the tension of the vapors of the liquid is dimi- 
nished, and by so much the more, when there remains a 
large quantity of the other liquid in the liquid state; the at- 
traction being so much the greater as the attracting liquid is 
more considerable. 
The boiling of two liquids which mix does not depend then 
solely upon the elasticity of the vapors of each of the two li- 
quids, as that takes place when the liquids do not mix, but 
likewise on the mutual attraction of the two liquids, which 
changes with their change of proportion. For a certain pro- 
portion of the liquids, boiling commences at a temperature at 
which the sum of the tensions which each liquid takes, by its 
attraction for the other, is equal to the atmospheric pres- 
sure. If, at this temperature, the proportion of the vapors 
produced is not the same as that which exists in the remain- 
ing liquids, the proportion of the remaining liquid will be 
altered. This changes the attraction which each liquid has upon 
the vapor of the other, the proportion of the vapors of each 
liquid, and the temperature at which the sum of their tensions 
