1887.] 
Mr J. Y. Buchanan on Ice and Brines. 
131 
the salt found in it in the solid state either as a crystalline hydrate 
or as the anhydrous salt, hut most probably as a hydrate. In 
dealing with the subject, Dr Otto Pettersson ( Water and lee , 
p. 302) quotes my observations, and also rejects the view that 
“ sea-ice is in itself wholly destitute of salts, and only mechanically 
incloses a certain quantity of unfrozen and concentrated sea- water.” 
He founds his belief on the fact that numerous analyses of speci- 
mens of sea-water ice have shown that the constitution of the saline 
contents of different specimens of ice differs for each specimen, and 
is always different from that of the saline contents of sea-water. 
Were the salinity due to inclosed unfrozen and concentrated sea- 
water, we “ ought to find by chemical analysis exactly the same 
proportion between Cl, MgO, CaO, S0 3 , &c., in the ice and in the 
brine as in the sea- water itself.” He quotes numerous analyses 
of specimens of sea-water ice from the Baltic and from the Arctic 
Seas to show that this is not the case. Calling the percentage of 
chlorine in each case 100, he found in various sea- waters the per- 
centage of S0 3 to vary from 11 ’49 to 11*89. In specimens of sea- 
water ice it varied from 12*8 to 76*6, and in brines separating from 
the ice and remaining liquid at — 30° C. it varied from 1*14 to 1*16. 
This argument appears conclusive. In order to explain all the 
phenomena observed in connection with sea-water ice he cites 
Guthrie’s investigations, which went to show that, in freezing 
saline solutions, under a certain concentration, pure ice is formed at 
a temperature which falls from 0° C., when the amount of salt 
dissolved is infinitely small, to a certain definite temperature when 
the solution contains a certain definite percentage of salt. Further 
abstraction of heat then produces solidification of the solution as a 
whole, in the form of a crystalline hydrate, of constant freezing- 
and melting-point. To such hydrates, Guthrie gave the name of 
cryohydrates. Pettersson quotes the following as being particularly 
applicable to the case of sea-water : — 
The cryohydrate 
Contains per cent. 
Solidifies at 
of 
of water. 
°C. 
NaCl . 
76-39 
-22 
KC1 
80-00 
-114 
CaCl 2 . 
72-00 
-37-0 
MgS0 4 . 
78-14 
- 5-0 
Na 2 SG 4 . 
95*45 
- 0-7 
