Laws of Molecular Force. 



285 



of W, X, and A, as deduced from measurements at 15°, ought 

 to be reduced by the factor '6/2i, or 1/2, to give the desired 

 values. Now in the case of homogeneous liquids in the 

 equation l = cuv^lm~s giving I in terms of the megadyne we 

 found a value 5930 for c/2, with the megamegadyne as unit 

 of force c/2 — '00593 ; and we can use this same value in the 

 case of solutions after we have halved our values of A, or 

 doubled those of cA _1 so far given ; hence using the values 

 of cA- 1 so far given we get M^='00593M 2 /cA~ 1 . 



Fortunately, a test of this argument is made possible by 

 means of Traube's data for the surface-tension of solutions of 

 certain organic acids and sugars, for which the values of 

 •00593M 2 /cA _1 are given in the following Table, as well as 

 values of S found by the relation M 2 /=6S (the term • 66 S 2 

 being omitted), and also values of S calculated from the 

 dynic equivalents in Table XXVI. 



Table XXXYI. 





Oxalic Acid. 



(00OH) 2 . 



Citric Acid. 

 3 H 4 OH(COOH) 3 



Glycerine. 

 C 3 H 5 (OH) 3 



Mannite. 

 . C c H 8 (OH) G . 



M.H 



19-4 



3-2 

 42 



43-5 



7-2 

 9-7 



33-5 

 5-6 

 5-0 



63-0 

 10-5 

 10-0 



S-M 2 //6 



S from dynic equiv. 





Tartaric Acid. 

 C 2 H 2 (OH) 2 (COOH) 2 . 



Dextrose. 



C 6 H 12 6 . 



Saccharose. 



MH 



38-9 



721 



12-0 



9-6 



1125 



18-8 

 18-1 



S-M 2 /6 



S from dynic equivalents 





7-4 



The agreement between the two sets of numbers is not all 

 that could be desired, but it is good enough to show that the 

 only part of M 2 Z effective in a solution is the linear term in 

 M 2 I=6S + *66S 2 ; and we have already seen that when the 

 molecules of ordinary liquids pair during liquefaction the term 

 '66S 2 is inoperative in the process, so that there is a certain 

 resemblance in the relations of two paired molecules and those 

 of solvent to those of substance dissolved. 



Returning to the inorganic compounds we can now tabulate 

 the absolute values of M% calculated according to the rela- 

 tion M 2 Z = •00593M 2 /cA~ 1 . The manner of calculation is best 

 illustrated by an example, say for KBr ; first *83 is taken as 

 the value for LiCl, and to it are added '90 and 1*56, taken 

 from Table XXXIII., as the differences for K and Li and for 



