താൾ:CiXIV132a.pdf/376

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LXIV

solidifying body takes place. Thus the volume of water increas
es in solidifying. 295. 296. Ice may even break a bomb-
shell, as Major Williams in Canada has proved, whose bomb-
shell was cracked and projected to a distance of 415′. The
same takes place with cast-iron, bismuth and antimony, whilst
gold, silver and copper contract; wherefore coins cannot be cast
but are stamped with a die.

§ 160. The expansion of Water by freezing may be ex
plained by the fact, that freezing is a kind of crystallization;
hence the molecules of water by arranging themselves in regular
groups occupy a larger space.

§ 161. Pressure may be substituted for heat and the point
of solidification or fusion lowered in doing so. By a pressure
of 8 atmospheres the freezing point of water may be lowered by
0.06° C (James and William Thomson) and by a pressure of about
13000 atmospheres Mousson succeeded in liquifying ice at a
temperature of -18°°C. In the first case a strong pressure pre
vented the molecules of water from arranging themselves in cry
stals, in the second case an immense pressure destroyed the
arrangement of crystals.

§ 162. Evaporation is influenced: a) by the renewal of
air, thus linen is hung out to dry, 314; use of fans. 326. If
the air is not renewed it will finally be saturated with vapour
and then the formation of vapour ceases 316, 322. Each space
can receive only a certain quantity of vapour, which is the greater
the warmer the vapour (see b) and the drier the air. The air
being thus an obstacle to vaporization, we may understand, that
in a vacuum all liquids are instantaneously converted into
vapour. 327. b) Evaporation is farther influenced by temper
ature: the higher it is the more abundant will be the vapour
produced, 316; c) by the extente of the surface. 315. (Salt

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