and the Surface- Tension of Solutions. 481 



theoretical equations. There is no theoretical reason why 

 there should be the two values 13 and 19 for the ratio unless 

 it be that b is not strictly a 2 /p 2 2 . But in the next comparison 

 to which we proceed we can see more light as to the meanings 

 of b and c; for if c is really iA 2 (a 1 a 2 )^//? 1 /?2(iAi2A 2 )*, then 

 («! being 7-5 and Pl being 1-0) c(p 1 /a^)M 2 (M a /p 2 )-t + (M. a 2 h)* 

 should be proportional to 1 A 2 /( 1 A 12 A 2 )* ; the values of this 

 ratio are : — 



Table V. 



NaCl. 



KC1. 



NaN0 3 . 



KN0 3 . 



MgCl 2 . 



CaCl 2 



7-8 



8-3 



64 



77 



7.4 



7-2 



SrCl 2 . 



BaCl 2 . 



Na 2 C0 3 . 



x 2 co 3 . 



Na 2 S0 4 



K 2 S0 4 



5-8 



7*4 



1-9 



4-3 



4-35 



40 



The ratio for all the compounds of the monobasic acid 

 radicals is approximately constant with a mean value 7*25, 

 while for the compounds of the dibasic acid radicals excepting 

 Na 2 C0 3 the ratio is near the mean 4*2 (Volkmann draws 

 attention to the difficulty of getting reliable measurements of 

 the surface-tension of solutions of Na 2 C0 3 ). There is enough 

 regularity in these results to show that the values of c are 

 probably iA 2 (a 1 « 2 )2/iOi/y 2 ( 1 A 12 A 2 )*, and that therefore the 

 irregularities in Table IY. are probably due to experimental 

 error or to some minor theoretical imperfection in (8) which 

 would have a large disturbing effect on the sensitive b. There 

 is no a priori reason why 1 A 2 /( 1 A 12 A 2 )^ (and therefore the last 

 ratio) should have the same value for different types of com- 

 pound, so that there is nothing inconsistent with theory in 

 the occurrence of the two values 7' 25 and 4*2, whereas the 

 two values 13 and 19 in Table IV. are inconsistent unless the 

 difference between them is due to causes not taken account 

 of in (8). It is a curious fact that the ratio 



for compounds such as MgCl 2 should range itself with that for 

 Na 2 S0 4 , while the ratio &*M 2 (M 2 //o 2 )-*-r- (M 2 2 / 2 )^ for the type 

 MgCl 2 detaches itself from that for the type Na 2 S0 4 . If b is 

 really a, 2 /p 2 2 and c is iA 2 (a 1 a 2 )^/p 1 )0 2 ( 1 A 12 A 2 )^ then the ratio of 

 the ratios gives the value of 1 A 2 /( 1 A 12 A 2 )*, which for the com- 

 pounds of monad metal with monobasic acid radical is 7'25/13 

 or *56, for compounds of dyad metal with dibasic acid 7*25/19 

 or *38, and for compounds of monad metals with dibasic acids 

 4*2/19 or '22. But we will return to these points later on. 



If we desire to test our conclusions so far by applying them 

 to other substances, we find ourselves somewhat restricted, 



