On the Saturation of Salt -Solutions. 71 



where the lists were complete was struck by the regular in- 

 crease of the mean molecular volume with the concentration, 

 and that this increase was a gradually decreasing quantity. 

 In order to study this point more closely I tried to find inter- 

 polation formulae that would express with satisfactory accuracy 

 the molecular volumes of solutions containing various amounts 

 of different salts. 



The most satisfactory form of formula I found to be 



M.Y. = 1800 + na + n 2 /3-n 3 y, 



where a, j3 } and y are constants depending on the salt ; 

 therefore 



r = na + ri 2 /3 + n 3 <y, 



V 



- —a + n6—n 2 y. 

 n 



The following tables L, II., III., and IV. contain the found 

 and calculated values for NaCl, KC1, NaN0 3 , and KN0 3 , in 

 solutions of strengths varying from 1 molecule up to the 

 saturated solution. The last column in each table contains 

 the molecular volume with which each successive molecule 

 enters into solution, a point to which I shall return later. 



The agreement between the found and calculated results 

 is on the whole good except in two cases, the saturated solu- 

 tions of NaCl and KC1, where the difference reaches 0*15 per 

 cent, and 0*2 per cent, respectively. That this is the case will 

 not surprise any one, for density determinations of saturated 

 solutions are carried out only with the greatest difficulty, and 

 are apt to be too low, thus rendering the molecular volume 

 too high. 



Table I. NaGL 





M.V. 



M.V. 



A. 



r 





11. 



found. 



calculated. 



n 







1 



1817-5 



1817-4 



-o-i 



17-4 



2 



1836-3 



1836-1 



-0-2 



18-0 



18-7 



3 



18560 



1855-9 



-01 



18-6 



19-8 



4 



1876-2 



1876-6 



4-04 



19-2 



20-7 



5 



1897-4 



1898-1 



+07 



19-6 



21-5 



6 



1918-8 



1920-0 



+ 1-2 



20-0 



21-9 



7 



19409 



1942-2 



+1-3 



20-3 



22-2 



8 



19636 



1964-5 



+0-9 



20-6 



22-3 



9 



1986-1 



1986-6 



+0-5 



20-7 



22-1 



10 



2009-2 



2008-4 



+0-8 



20-8 



21-8 



11 



2032-7 



2029-6 



+31 



20-9 



21-2 



12 



1 





2050-0 





20-8 



20-4 



«= 16-634. j3= 0-7711. 



=0-0351. 



