[SATTERLY] SURFACE TENSION, ETC. 85 



"From Regnault's empirical formula the latent heat of aqueous 

 vapour at 86°F. is 1054. One cubic inch of water thus heated is 

 equivalent to one cubic inch of Avater at temperature 86° raised 

 through 1054X772 X 12 inches vertical Hence 



1054X772X12 



.04546 = 214,800,000 



is the number of layers of a molecule in one cubic inch, and the cube 

 of the reciprocal of this is the absolute volume of one molecule of 

 water at the temperature 86°. The process expressed by symbols 



is m^= { — ) in which L is the product of the latent heat by 12 



times 772. Q the quotient of capillarity and m^ the molecular volume 

 expressed with reference to a cubic inch as unit." 



( 



Expressed in modern language this would read m^ = {~~: J • 



Waterston's result expressed in cms. is m = 1.47 X 10"^ cm. He worked 

 out a similar value for alcohol, taking (2 = 228 and obtained 



1 . 



^î= 1 An rxr^r^ rv^.i iuch which = 1 .74 X 10 cm. 

 146,000,000 



Waterston also compared the molecular volumes of water and 

 alcohol. From the above calculations he found "ratio of molecular 



/146\3 1 

 volumes of water and alcohol equal to \^rj = 'ô'Jô • ^^ ^Iso com- 

 putes it from 



"Specific gravity of water at 68°F. = 1.000 



" 86°F.= .998 

 " " alcohol " 8G°F.= .780 

 " " steam =9 



" " alcohol vapour =23.16 



9X.780 1 " 



whence ratio of molecular volumes = 



23.16X.998 3.29 



He mentions that the two methods of calculating the relative molecular 

 volumes did not agree with turpentine, ether, and acetic ether and 

 ascribes it to one part of the molecule separating from the other 

 while rising into vapour. "We must be prepared to view as possible 

 a certain absorption of heat in partially separating, not only the 

 molecules, but their constituent chemical elements, because the 

 application of extreme heat alone is capable of effecting their com- 

 plete separation." 



