THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



DECEMBER 1895. 



XLIV. Molecular Force and the Surf ace-Tension of Solutions. 

 By William Sutherland *. 



IN " The Surface-Tension of Mixed Liquids " (Phil. Mag. 

 Aug. 1894) it was shown that for a mixture of liquids 

 1 and 2 containing in one gramme p x gramme of 1 and p 2 of 2, 

 the surface-tension a. and the density p are connected with 

 the corresponding quantities for the two liquids by the relation 



/ 9 2 / 2 , 2/2. 2iA 2 /a 1 a 2 \J(m 1 /j() 1 )* + (wij/p ( ,)* 



«p 2 =pMI Pl 2 +p 2 2 « 2 /p. 2 2 i- -j- —ptfJ—^j \ ™ \ 2HJ 



where SiAxm^/r 41 , 3 2 A. 2 m 2 2 /r 4 , and 3 1 A 2 wiw 2 /?' 4 express the 

 molecular force between molecules of 1 and 1 ; 2 and 2, and 

 1 and 2 at distance r apart. It was also shown by experi- 

 ment that for most pairs of normal liquids 1 A 2 2 = 1 A 12 A 2 , and as 

 Ave have approximately (m l /p l ) * + (m 2 /p 2 ) * = 2(wi 1 //o 1 ) * (rn 2 /p 2 ) % 

 we get 



a/p 2 =(p l a 1 */p 1 +p 2 ci 2 >/p 2 ) 2 (7) 



The experimental proof of the relation 1 A 2 2 = 1 A i2 A 2 consisted 

 in showing that for mixtures of 24 out of 28 pairs of liquids 

 the ratio 1 A 2 /( 1 A 12 A 2 )* had a value between *9 and 1*1. We 

 can make the proof more complete by means of some data 

 determined by Prof. Ramsay and Miss Aston (Proc. Roy. Soc. 

 lvi.). In the following table the first liquid of each pair is I, 



* Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 40. No. 247. Dec. 1895. 2 L 



