A Theoretical Treatment of Mixed Smokes as Ice Nuclei

Johnson, Duane M.

doi:10.21236/ad0669435

Cited by 1 publication

(2 citation statements)

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“…As additional water is accumulated the aerosol will suffer dissolution which will result in precipitation of silver iodide within the droplet (Davis, 1972). Johnson (1968) has made calculations on an expected temperature decrease due to the dissolution process of the aerosol. The exact value for a freezing temperature is dependent upon the size of the droplet and concentration of KI in solution.…”

Section: Ice-nucleation Activitymentioning

confidence: 99%

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The phases of the AgI–KI–H₂O system

Johnson¹

1975

J Appl Cryst

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An X‐ray diffraction study of the AgI–KI–H2O chemical system was conducted by injecting an acetonic solution of a 2:1 mole ratio of AgI:KI directly upon an inert substrate thermally strapped to a thermoelectric cold stage. The atmosphere over the stage was controlled from 0.6 mb water vapor pressure to saturation while the temperature was varied from −22 to 25°C. Under these conditions four distinct crystalline phases are formed. Crystals of phase AK (KAg4I5) appear as the acetone evaporates. Moisture available from the ambient atmosphere functions as a catalyst as the newly formed AK transforms to phase BK (K2AgI3). At higher vapor pressures a second transformation results in phase CK. All phases break down and form an aqueous solution of KI plus equant AgI crystals (complex DK) at saturation vapor pressures. Another hydrous phase EK occurs below 0°C. The most probable composition of phases CK and EK is KAg2I3.H2O and KAg3I4.8H2O respectively. Nucleation studies show that the KI system is a poorer artificial nucleant of ice than the NH4I–AgI system above −10°C. Kinetics of the system suggest an absence of any free AgI for aerosols released from airborne platforms or from ground seeding stations.

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Section: Ice-nucleation Activitymentioning

confidence: 99%

“…Such a mechanism of condensation-freezing has been proposed (Fletcher, 1970). Johnson (1968) has made calculations on an expected temperature decrease due to the dissolution process of the aerosol. This temperature decrease should enhance ice formation of the droplet.…”

Section: Ice-nucleation Activitymentioning

confidence: 99%