482 Mr. W. Sutherland on Molecular Force 



because most of the available experiments relate to com- 

 paratively dilute solutions, and to only one concentration, or 

 to concentrations which vary but little. Under these circum- 

 stances the term in p 2 2 in (8) becomes small compared to that 

 in p x p 2 , but not so small that it can be actually neglected ; we 

 can take account of it approximately by writing (8) in the 

 form 



2 A iA 2 



*lp 2 = pi*i/pi + rKHhkPW&^lPiP* + a \ p *Ip* d A 2 7iAi 2 A 2 ) 



and then in the last part of the last term give 1 A 2 2 /iA, 2 A 2 the 

 values we have found, namely, *56 2 for the type NaCl, *38 2 

 for the type MgCl 2 , and *22 2 for the type Na 2 S0 4 ; with 

 thfse values the last equation becomes a quadratic for 

 iA 2 a 2 5//> 2 ( 1 A 12 A 2 )^ if the surface-tension a and the density p 

 have been measured for a solution of strength p 2 . 



Thus for the haloid compounds of Li, Ka, and K and their 

 nitrates we have 



2 A 1 A 2 



»/p 2 =Pi"Jpi* + ^A 12 l 2 )i ^V^Mlpip2 + .-gg-j -\^P 2 ^P2, (1 



which with Rontgen and Schneider's data (Wied. Ann. xxix.) 

 gives the following values for 1 A 2 a 2 i//3 2 (iA 12 A 2 )*, and for the 

 ratio of M 2 (M 2 /p 2 )-i 1 A 2 a 2 Vi0 2 (iA 12 A 2 )* to (M 2 2 / 2 )i given in 

 the last row. 



Rontgen and Schneider's measurements were made at about 

 18° C. ; and their values of a are given in an arbitrary unit 

 which makes that for water 111*45, but taking this in mgrm. 

 per millim. as 7*464 according to Volkmann, all Rontgen and 

 Schneider's values of a for solutions can be expressed in 

 mgrm. per millim. 



Table VI. 



LiCl. LiBr. Lil. LiN0 3 . NaCl. NaBr. 



P 2 -060 *115 -107 094 -080 -134 



P 1-033 1087 1-138 1-056 1057 1111 



a 7-698 766 7"58 7'645 7702 7*679 



jA^/p^jA^A^ 1-89 1-05 -80 1-43 1-33 -90 



(M 2 2 Z 2 )2 4-5 51 6-0 60 56 6-2 



10*7 10-3 9-7 9-4 80 8'3 



Nal. NaN0 3 . KC1. KBr. KI. KNO,. 



p. 2 -183 -113 -100 -151 -199 131 



P 1-161 1-078 1064 1-118 1-166 1085 



a 7*621 7-647 7-685 7661 7'605 7'625 



,A 2 a^ / > 2 ( 1 A l2 A 2 )^ -745 1-18 1-37 -966 -82 1-22 



(M 2 */ 2 )5 71 7-1 6-7 7-3 8-2 8*2 



8-4 7-7 8-4 -8*4 8-5 7*8 



