RESEARCHES ON EVAPORATION AND DTSSOOTATION. 325 



the boiling-point under atmosplioric pressure witii those 

 of other observers ; but it may be stated that our result 

 differs far less from the observation of Pavre and Silber- 

 mann than theirs does from that of Berth elot. 



Messrs. E. and L. Natanson have recently published a 

 research on the vapour-densities of nitric peroxide (NO, or 

 ■'^2*^''i)j which, taken in conjunction witli oxperimonts of ours 

 on the vapour-pressures of that body, show that nitric 

 peroxide behaves like acetic acid, the density of its saturated 

 vapour rising with fall of temperature, but in their experi- 

 ments never exceeding that of NgOj. 



It appears to us that these results negative the chemical 

 explanation of the constitution of liquids; or, to confine 

 ourselves to known cases, of the alcohols and of other. 

 The molecules of these liquids cannot, we think, be re- 

 garded as complex, consisting of gaseous molecules in 

 chemical combination with each other, as, for example, 

 ra Ca H(. 0, where n is any definite number. Wo believe 

 rather that the physical explanation of the nature of 

 liquids is the correct one, and that the differences between 

 liquids and gases lies merely in the relative proximity of 

 their molecules. The chief argument for this view is that 

 it is difficult to conceive that the rise of vapour-density of 

 acetic acid both at high and. at low temperatures can be 

 produced by the same cause under conditions so radically 

 different; for at high temperatures we have conditions 

 unfavourable to chemical combination, but, owing to the 

 necessarily high pressure, the molecules are in close 

 proximity ; whereas at low temperatures, the conditions are 

 favourable to chemical combination, while the molecules, 

 owing to the corresponding low pressures, are very far 

 apart. The increase in the density of the saturated vapour 

 of acetic acid at low temperatures is therefore, in all pro- 



