rca‘ CRYSTALS.
.
.
25
that both processes cari take provided that the temperature is
This process can easily be examined
expenmentally because the growth rate of crystals from the vapour in air is limited by the
di‘us1on process
and is smaller by about a-fac‘tor‘of about 106 at—IO °C compared With
crystals growmg in supercoOled-rwater,,
'
'
…
.
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«
-
.
The apparatus used for these:studies is shown ingure 3 4.
…
The temperature of the
crystal and the supersaturation Could be controlled independeny.
Many substances
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Pérspèx
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cover
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Sub$trote
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microscope
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stage
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>Brass
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,
.
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?Poxolîn însulaon
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_
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saturation depends on the temperatureàerencebemæncwstalandthe1cewgs
_
Which were eective in nucleating ice?cry$“iàl$ werefoundto
a crystallOgraphic plane
=
_
j
__
similar to one in the ice lattice. .iÎTŸVO
at
'
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—
.
Occur on a hexagonal basal
cr '
'
and basal plane co‘uld
crystal (gure…5): _
_
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Some substances which
.
‘
CdIz would do so
Ï
compounds are hexagonalAgl(thresholdtemperature—4C),PbIz(—6°C)andCus
,
(—6C) with
These substances wereabletonuc1eatewaterdropscondensed0nthesurfacesdown