Geoscience Reference
In-Depth Information
used. Formvar is a brand name of polyvinyl formal resin. A solution was
prepared with 0
10
−
6
m
3
of chloroform. A thin
layer of this solution was coated in two slides at a time, and these were kept
in a tray near the floor of the vessel to collect the signature of the crystals
falling there. The lid over the tray can be opened or closed using external
control. Crystals were collected for 2 min only after seeding was done. When
the slides were brought outside after the experiment, the chloroform quickly
evaporated leaving behind a plastic film of formvar. On the other hand, the
ice part of crystals melted to water. Details about these formvar-coated
slides are already available in the literature.
25
,
26
The slides were then kept inside a desiccator with sucient silica gel, so
that water would evaporate and be quickly absorbed by the gel. A replica
of the arrested crystals is then retained in the slide, and in the case of
heterogeneous nucleation the nucleating agent is left behind at the core.
One can observe the replicas through a microscope.
The concentration, size, and basic habits of the crystals in a slide were
noted at different temperatures. The microscope being used here has a
magnification of 400. On each slide, 10 randomly chosen fields of view are
taken for counting.
To study the nucleation ability of DMSO-coated Ammonium Sulfate
dust, 5 g of Ammonium Sulfate dust was coated with 0.7 g of DMSO in
liquid state. Ammonium Sulfate dust had dimension in the range of 0.1-
0.7
µ
m. In fact, the above-mentioned amount of DMSO was just sucient
to coat fully the dust particulates of Ammonium sulfate. An amount of
20
10
−
3
kg of formvar in 10
.
4
×
×
10
−
6
kg of coated Ammonium Sulfate was sprayed inside the vessel in
one stroke, keeping consistency with the first experiment. All the conditions
were kept identical like the experiment with DMSO only. Like the first
experiment, the concentration, size, and basic habits of the crystals formed
in a slide were noted at different temperatures.
×
3. Theory for Optical Parameters
A detailed theory for the optical parameters is already available in the
literature.
21
The effective volume scattering coecient, when the angle of
scattering is
, is evaluated following the procedure given there.
The extinction coecient is determined using Beer's law,
θ
I
0
e
−σT
,
I
=
