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ine) occasions no great discrepancy in the behavior of the
liquid water IV from that of pure water. In the solid state
however, the difference is very considerable.
CHAPTER 5.
Chemical changes in the composition of water
caused by freezing.
From the preceding chapters the reader must have
discovered the weighty influence, which the saltness of the ice,
however slight it be, has upon its physical properties. I hope,
it will appear from this exposition, that the composition of
the sea-ice is a subject of such importance, that it ought to
attract the attention of the chemists as well as the physicists
more and more. For my part I confess, that I write this
chapter more in the hope of winning the interest of my
readers for the following questions than from any hope I have
of being able to give a conclusive answer to them myself.
Is the salt a constant and normal component of the sea-ice?
Mr. F. Guthrie tried to decide this question by artificial
freezing of sea-water from Dover. The ice, which formed
freely from the sea-water, contained about 4/.i of the usual
percentage of salt, but a part of it, which had been pressed
between linen and flannel in a screw-press, was found to hold
•only ’/is. Guthrie observes, »that the almost undiminished
saltness of the unpressed ice is due, as suggested by Dr.
Rae, to the entanglement amidst the ice-crystals of a brine
richer in solid constituents than the original water itself.
Such brine, which is here squeezed out in the press, drains
in nature down from the upper surface of the ice-floe by
gravitation and also is replaced by osmic action by new
seawater, which again yields up fresh ice, so that, while new
floes are porous and salt, old ones are more compact and
much fresher, as the traveller observed». All other observers,
except Dr. Buchanan,1 agree in the opinion, that the saltness
of the sea-ice is due to the entanglement of salt brine in the
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