weilawei - 13-12-2017 at 10:12
In the course of making AgNO3 to silver flasks for Christmas ornaments, I wound up with small droplets on my hotplate, which then decomposed to
elemental Ag. I'm considering 70% HNO3 or possibly 30% HCl followed by 29% ammonium hydroxide, but I'm looking for a method that won't generate NO2 or
Cl gas. (It's cold outside, but if I must, ultimately I'll work outside as I did before to make the AgNO3.) However, if anyone can suggest a less
toxic, even if slower, method, I would prefer that.
Meltonium - 13-12-2017 at 18:04
Why do you need to clean it off? Are you trying to recover it, or are you trying to just leave a nice, clean hotplate? I would suggest sandpaper if
you're not trying to do anything chemical.
weilawei - 13-12-2017 at 18:10
I'm attempting to leave a nice clean hotplate without damage to the enamel. I have no interest in recovering the silver. It's a minute quantity, and I
don't need any more. I did order a couple polypropylene scrubbers (which will have the foam core removed from them), in the event I decide to give
dilute nitric acid (perhaps 10-20%) a go. Apparently, they're fairly resistant up to 50%, according to several compatibility charts.
I had considered sandpaper, but worried about scratching the enamel off. A very fine grit might do the trick nicely.
Once the flasks are silvered, I'll post a separate write-up with plenty of pictures.
[Edited on 14-12-2017 by weilawei]
clearly_not_atara - 13-12-2017 at 18:25
Silver forms complexes with succinimide and with dimethylhydantoin which solubilize it. As these anions are inert to hydrogen peroxide, I suspect you
could dissolve the silver with a mixture of hydrogen peroxide and sodium succinimide, which may even be somewhat selective.
http://www.technic.com/apac/sites/default/files/assets/pdfs/...
Chemvironment - 13-12-2017 at 20:02
In my experience the only way to have a clean and undamaged enamel on your hotplate is to not use it. I would try gently scrubbing it with something
slightly abrasive.
weilawei - 14-12-2017 at 04:45
Yeah, but I bought it clean 5 years ago, use it all the time, and it was still clean (looked nearly new). I typically scrub with a sponge after every
use, but that's not going to do it this time. I'm pretty picky about cleaning my equipment. Better results, less questions and repairs.
[Edited on 14-12-2017 by weilawei]
Rhodanide - 14-12-2017 at 06:39
If it were AgNO3 then I'd suggest dil. NaOH, but seeing as it is elemental Ag stains, then yeah I'd go with HNO3 and THEN NaOH soln, then wipe off the
Ag2O left. Silver is tricky!
MrHomeScientist - 14-12-2017 at 07:33
If it's minute quantities, don't worry about NOx.
Melgar - 15-12-2017 at 09:47
Silver salts (mainly nitrate) will permanently stain porcelain. I learned this the hard way when pouring some out in the sink. The only thing that
can remove it is hydrofluoric acid, mainly because HF will dissolve the enamel. Soaking in dilute, agitated alkali cyanide solution might also work,
since that's how gold and silver tend to be extracted from their ores. Both of these solutions are quite extreme though, and you'll probably
eventually have to learn to just live with it.
The AgNO3 typically diffuses into the enamel before turning into elemental silver, which is what makes it so difficult to remove.
[Edited on 12/15/17 by Melgar]
unionised - 15-12-2017 at 11:18
Let your hotplate wear its silver badge of honour with pride.