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Why does it not simply form a solid powder at the bottom of the flask?

Does silver also stick to the glass in other silver precipitating reactions?

EDIT: My question is definitely not the same as the one linked (which btw does not have an answer and is inactive for three and a half years).

Normal precipitation of silver from silver ions results in a black powder and no mirror.

As pointed in the comments, kinetics seems to play a major role here, with slow precipitation being key to achieve a mirror.

So why is it that a slow reduction of silver ions make them deposit on the surface of the glass?

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    Well, only logical explanation is that the reaction happens on surface, not in the bulk of solution, I do wonder why it happens like that, though. – Mithoron May 25 '20 at 00:33
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    This has some information: https://www.compoundchem.com/2017/09/06/silver-mirror/. Stannous chloride solution is also commonly mentioned as a preparation step: the glass surface is rinsed with this reducing agent. – Ed V May 25 '20 at 01:41
  • @EdV The important hint in there might be that the diammine complex is more stable than the aqua complex, and leaving out the ammonia does lead to a black suspension. – Karl May 25 '20 at 07:17
  • It is qualitative but whatever reason nucleation centers being at the glass surface isn't surprising. True is that the film forming is quite peculiar of the test. – Alchimista May 25 '20 at 11:04
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    @Karl I agree: it was the lower right corner that had a little tidbit of maybe helpful insight. There is certainly no problem making silver nanoparticles or growing a silver tree: I have done these as demos. And adding zinc metal to a silver nitrate or nitrite solution just makes silver powder. So there must be something about kinetically hindering the process to ensure slow and orderly deposition. I hope someone provides a correct answer for this one! – Ed V May 25 '20 at 12:42
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    @EdV Me too! But I guess someone has to write a new question that already clears the more obvious points. OP: Please update, then we can vote to reopen! – Karl May 25 '20 at 19:59
  • @Karl Sorry, I just got distracted by a message to vote for moderators in the EE stack exchange. I see nothing that I can add to elucidate how the silver mirror forms. Maybe this could be studied using things like SERS, but I have nothing substantive to go on. I know people still make relatively large silver mirrors for fun, but presumably they are following prescriptions or old recipes known to work. In any event, an interesting question that does not directly involve honey or homework. ;) – Ed V May 25 '20 at 20:17
  • @EdV Silvered (Dewar) lab glassware is still made this way, and amateurs grinding large telescope mirrors certainly do the same. I once tried to find scientific work on how to control the thickness of such silver films, wanting a dewar with specific a.c. electrical properties. Did´t find anything really useful, however. Very mysterious. ;-) – Karl May 25 '20 at 20:47
  • @Karl Just found a scan of a yellowed 1931 article from the old N.B.S. Journal of Research: https://nvlpubs.nist.gov/nistpubs/jres/7/jresv7n5p935_a2b.pdf. This must have been studied before 1931, but the available techniques back then would have been problematic. Even pH meters date from around 1931. – Ed V May 25 '20 at 21:46
  • @Karl Another paper from 1911: http://articles.adsabs.harvard.edu//full/1911PA.....19..327C/0000329.000.html. And it references even older work more than half a century before 1911. But no luck finding out why this process, which appears almost alchemical, works. There is a sentence in German on the first page that my college German is too long gone to translate. – Ed V May 25 '20 at 22:10
  • @EdV Quincke says that all those methods for silvering occasionally fail, or give substandard mirrors, and one is unable to find out a proper reason for that. Alchemy. ;-) – Karl May 26 '20 at 18:19

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