324 EESEARCHES ON EVAPORATION AND DISSOCIATION. 



ing-points tinder atmospheric pressure. With methyl and 

 propyl alcohols similar results wore obtained. 



With acetic acid the results wcro very diiferent. On 

 raising the temperature above 150°, the density of the 

 saturated vapour increased as with other liquids ; but below 

 that temperature (at which the vapour-density was 50-06, 

 the calculated density being 30) the vapour-donsity, instead 

 of continuing to fall, rose more and more rapidly with fall 

 of temperature, until at 20° it was approximately 5i), and 

 apparently, from the form of the curve, was continuing to 

 rise more and more rapidly with fall of tompcraturo 



30 m io to 



Fig. 4. Vapour JJeiisities oJ Acetic Acid (H = 1 at t" and p mm.). 



(Fig. 4). It may bo mentioned that direct observations by 

 Binoau give nearly the same value. 



The curve representing the heats of vaporization of acetic 

 acid at various temperatures also differs entirely in form 

 from those of the alcohols and ether; for it exhibits a 

 maximum at 110°, and decreases both with rise and with fall 

 of temperature (Pig. 3). It is difficult to draw any conclusion 

 from a comparison of our measurements of this quantity at 



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