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I have read a teensy bit of the subject matter and the explanation they provided for silver iodide's ability to being a good site for ice to form is because of its size resembling an ice nucleus.

How exactly does silver iodide adsorb water onto its surface? Is it hygroscopic? Ice crystals growing larger due to vapour deposition or rapid freezing of supercooled water upon contact with ice makes sense. But how does silver iodide do it?

If the hygroscopic properties of silver iodide are what enables it to seed clouds, can the common salt also be used to seed clouds? I do apologize as the question wasn't aptly structured. Please do help in understanding this!

P.S. I found an article which I find is relevant to this question [1], but unfortunately, I'm not experienced enough to go about reading scientific articles.

Reference

  1. Pena, R. G. D.; Caimi, E. A. Hygroscopicity and Chemical Composition of Silver Iodide Smoke Used in Cloud Seeding Experiments. Journal of the Atmospheric Sciences 1967, 24 (4), 383–386. DOI: 10.1175/1520-0469(1967)024<0383:HACCOS>2.0.CO;2.
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  • $\begingroup$ No, it's rather the opposite. $\endgroup$
    – Mithoron
    Commented Mar 25, 2021 at 20:25

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Silver iodide is not hygroscopic. It is used to seed clouds, because when the atmosphere is saturated with water vapor, liquid water should start condensing. But to do this, it needs a seed, a place when the first molecules will start to condense. No water molecule feels that it should be the first one to show other molecules where to be condensed. But, as silver iodide has the same hexagonal shape and same dimensions as snow, it may make believe it is an ice crystal. And the neighboring water molecules will be mistaken, follow the example and deposit on it. The common salt cannot do this. It does not look like ice.

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