134 Proceedings of Royal Society of Edinburgh. [mar. 21 , 
the ratio of S0 3 to Cl found by analysis, the chlorine being set 
down as 100 ; thus, in I. the percentage of chlorine found in the 
crystals, melting at the lowest temperature, was 1*497, and that of 
the S0 3 , 0*174 ; the ratio (R) is therefore 11*62. 
Table I . — Freezing Sea-Water — Analyses of Fractions. 
No. of Experiment, 
I. 
II. 
III. 
IV. 
Nature of Water, 
Forth 100 %. 
Mother-liquor. 
Clyde 100 %. 
Clyde 50 %. 
w. 
R. 
w. 
R. 
w. 
R. 
W. 
R. 
Original water, 
300 
11*83 
90 
11*67 
300 
11*58 
300 
11*21 
Mother-liquor, . 
J 170*6 
11*67 j 
• • • 
11*83 
102 
11*57 
78 
11*67 
Drainings, 
• • • 
• • • 
94 
11*56 
109 
• . . 
Crystals, . 
106 
11*62 
23 
11*22 
97 
11*67 
106 
11*4 
jj 
22*5 
11*11 
... 
... 
... 
... 
... 
... 
It will be seen that the ratios (R) found for mother-liquor, 
drainings, and ice agree with one another quite as closely as those 
found in samples of pure sea-water from different localities. It is 
to be remembered that in these experiments the water was frozen 
gently — that is, the rate of abstraction of heat was low, the tem- 
perature of the freezing bath being regulated so as to be about 2° C. 
below the freezing temperature of the solution. Much of the error 
and uncertainty about the freezing of saline solutions arises from 
the violence of the methods employed. Judging then by the con- 
stancy of the relation of the percentage of Cl to S0 3 , we see that in 
sea- water, frozen at moderate temperatures, the composition of the 
saline contents of the original water, the mother-liquor, and the ice 
is identical; and we are justified in concluding that it is probable 
that the saltness of the ice is due to unfrozen and concentrated sea- 
water adhering to it. Ice forming in even very weak saline solutions 
closely resembles snow (which is ice forming in air), and has the 
same remarkable power of retaining mechanically several times its 
weight of water or brine. 
If we assume that the ice formed in freezing sea-water is pure ice, 
and that the saline ingredients are retained by the portion remaining 
liquid, we can calculate the amount of ice which has been formed if 
we know the salinity of the original water and that of the residual 
brine. In the case of sea-water the salinity varies directly with the 
