354 On the Theory of Surface Forces. 



" crumbling into molecules" If the temperature is higher the 

 considered kernel must be larger, the velocity o£ the molecules- 

 being greater. This consideration is also in accord with my 

 theory. Indeed, I have found that for a fixed temperature 

 the radius of a liquid drop of minimal size is of the same 

 order of greatness as that of the thickness of the plane 

 capillary layer at the same temperature. Now my formula 

 for the thickness h of the plane capillary layer becomes for 

 instance for ether 



»-{*&-"•}» 



ivnere 3 = rlr - and gives for T = 0*585 T 7 , or 0° Celsius r 



T 

 T* 



h =4*5 fxfx, while we have found for the R in the formula of 

 Kelvin, R = 10 /t/i. At the temperature T = 099T*, we shall 

 find: A = 55 fifi. R being of the same order of greatness 

 as />, we shall find about 100 /ul/jl for the order of greatness of 

 R at the temperature : T = 0*99Ti. The minimal size o£ a 

 liquid drop of ether at T = , 99T^ ; is therefore about the 

 thousandfold of the value at 0° Celsius. Further, the 

 critical density being about a third of the liquid density 

 at 0° Celsius, a liquid drop of ether, ivhicli has its minimal 

 size at T = 0'99Ta, must contain a number of molecules which 

 is the 300-fold of this at 0° Celsius. If therefore in the 

 immediate neighbourhood of the critical temperature con- 

 densation takes place, it begins with relatively large " drops " *. 

 In fig. 1 the points A 8 and C 8 give for a drop of minimal size 

 respectively the state in the interior of the drop, and in the 

 vapour which surrounds it. In the immediate neighbourhood 

 of the critical temperature, the parts C 8 K and A 8 H of the 

 curve in fig. 1 being small, the state (A 8 , C 8 ) for a drop on 

 one side and the state given by (H, K) on the other side are 

 not very different. Hence follows that a small variation of 

 the temperature t or of the pressure converts the state (H, K) 

 into the state such as (A 8 , C 8 ). 



In connexion with my observation on the relatively large 

 size of the drops which have their minimal size in the imme- 

 diate neighbourhood of the critical temperature, we have 

 therefore two conditions for the formation of mist. When 

 we make a corresponding observation for the pair of points 

 A,Ci in fig. 1, which gives the state of a bubble of minimal 



* These " drops " are, however, ultramicroscopic, and form therefore 

 firstly an invisible haze, which nevertheless by accumulations of several 

 u drops) " quickly passes into mist. 



t In this case we must consider the complete set of isotherms. 



