Volumes of Salt-Solutions. 
127 
viz. Tables II. and V., where the values of (K— Na) CI and 
K(N0 3 — CI) are least with the most dilute solution; and 
two cases where the reverse is the case, Table VI., where 
K f CI k^j and Na( CI ~-^ J have the greatest value when 
the solution is most dilute. If we compare the most concen- 
trated and the most dilute solutions of the same salt, we can 
ascertain what effect concentration has on the molecular 
volume of the salt. This is done in Table VII., where the 
volume of the water is assumed constant =1800. 
Table VII. 
X. 
Mol. toI. 
KC1. 
Diff. 
Mol. vol. 
NaOl. 
Diff. 
Mol. vol. 
KN0 3 . 
Diff. 
Mol. vol. 
KOI. 
Diff. 
0-5 
5-0 
27-08 
2997 
2-89 
17-08 
19-48 
240 
38-06 
41-35 
3-29 
27-08 
29-97 
2-89 
Mol. vol. 
KC1. 
Mol. vol. 
Mol. vol. 
NaCl. 
Mol. vol. 
1-0 
2-0 
27-67 
28-56 
0-89 
18-76 
20-05 
1-29 
17-52 
18-14 
0-62 
8-32 
9-66 
1-34 
The numbers in the columns headed Mol. vol. are the 
molecular volumes of one molecule of the salt in a solution 
which contains x molecules to 100H 2 O ; the difference is the 
increase of the molecular volume of each molecule produced 
by the increase in concentration shown by the column 
headed x. 
A glance at these differences will show the immediate 
reason of the increase or the diminution, as the case may be, 
of the differences between the pairs of salts, when the solution 
is concentrated. In the first two cases, (K — Na) CI and 
K(N0 3 — CI), the salt with the larger molecular volume has 
it increased by concentration at a rate faster than that of the 
other : and the cod verse is true with regard to K ( CI ~ ) 
/ SO \ \ 2 / 
and Na ( CI ^ I, for here it is the one with the smaller 
molecular volume on which the effect of concentration is 
more marked. 
To find, however, the real cause of this we must bear in 
mind that, in the first instances, it is the first member of each 
pair of salts that is least soluble in water, while in the latter 
it is the second member of each pair of which this is true. 
The solubilities in terms of salt-molecules to 100 water-mole- 
cules are approximately: — 
L2 
