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would be among the first to separate from the cooled sea-water
already at —0°.7 C. This agrees well with the table 1, of this
chapter, which shows, that of all the constituents of the
seawater the brines are most deficient in Na20 and SO3. The
percentage of sulphuric acid in ocean water is about O.2228
(calculated as SO3). Suppose all this to combine with its
equivalent of Na20 and freeze out as a cryohydrate in the ratio
[O.3954 % NaoO’-SO2 + 8.3947 % H2O] + 91.3... % aq.
(cryohydrate)1 (ice)
then 8.69 % of the frozen sea-ice ought to consist of the solid
cryohydrate of Na2S04 instead of pure ice with a few drops
•of concentrated brine, as is ordinarily assumed. It would be
impossible to explain, how an amount of O.3954 % of foreign
matter could so essentially modify the physical properties of
the ice, as is seen in the foregoing chapters, if the substance
was included in the ice as solid crystals or as adhering drops
of brine, but we will have no difficult}7 to admit, that the
presence of 8.69 % of a solid cryohydrate, which physically
and chemically is a different body from the pure ice, can
modify its properties considerably. Moreover this solid has
its melting point at —0°.7 C. Consequently it will endure in
the solid state as long as the ice itself. Other cryohydrates,
as for example MgS04, Mg Cl2, CaCl2, NaCl, which arise at
loAver temperatures, will consequently melt again long before
the rest of the ice. Therefore every rise of temperature will
promote the metamorphosis of the ice extraordinarily. The
cryohydrates of the chlorides will liquefy and escape, if any
chance is left to them. This is realized by the abnormal
contraction of the sea-ice by the fall of temperature, which
causes a strain and a bending on its surface, which finally
ends with its bursting and breaking up into remnants and
fissures. 2 When the temperature rises again, the liquefied
1 The reader will of course perceive, that I do not mean to say, that
the sulphuric acid of the sea-water freezes out at once as a cryohydrate at
— 0.°7 etc. but that I only wish to give an idea of the whole, very
complicated, process by the chosen example.
3 The uppermost layer of the ice, having acquired the temperature of
the air. will begin to assume the properties of a hard body and contract its
volume (while; the next layers, to which the atmospheric cold penetrates
more slowly, is still expanding’) and consequently breaks up into
innumerable rifts. In short I believe, that the regular expansion or contraction
seldom causes any violent dislocation of the ice. Such effects are due to
the great abnormal changes of volume, which take place in fresh-water ice,
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