Sciencemadness Discussion Board

mystery metal, resists nitric acid

ldanielrosa - 23-8-2015 at 17:08

Some time ago, I dissolved a Chinese silver spoon in nitric acid to verify the silver content. It came up about 70%, which I suspected from the markings on the stem.

I used copper wire to displace the silver, dried and weighed the precipitate. Then I dissolved the reclaimed silver in nitric acid again so that I'd have a supply of the nitrate salt. The solution was colorless (no copper), but some small portion wouldn't dissolve.

I set this aside, washed and dried it, then tried again. No reaction. Any ideas for an element that would behave this way?

xfusion44 - 23-8-2015 at 17:39

Maybe stainless steel or titanium - less likely.

Oscilllator - 23-8-2015 at 17:55

Since the material dissolved in nitric acid once, but then didn't dissolve the second time it it possible that the unknown material is some kind of contamination? I don't see any reason why something could be dissolved once but not twice.

blogfast25 - 23-8-2015 at 17:57

Quote: Originally posted by xfusion44  
Maybe stainless steel or titanium - less likely.


SS (Fe + Cr, mainly) dissolves in nitric in a jiffy. Ti forms insoluble TiO2 with nitric.

+++++++++++

Silver objects often contain small amounts of even 'nobler' elements due to repeated recycling and thus mixing with other silver alloys coming from jewellery, cutlery, ornaments etc. Commercial silver objects may thus contain Au, Pt and other 'nobles' that aren't soluble in nitric acid.

[Edited on 24-8-2015 by blogfast25]

fusso - 12-4-2018 at 12:06

Quote: Originally posted by ldanielrosa  
Some time ago, I dissolved a Chinese silver spoon in nitric acid to verify the silver content. It came up about 70%, which I suspected from the markings on the stem.

I used copper wire to displace the silver, dried and weighed the precipitate. Then I dissolved the reclaimed silver in nitric acid again so that I'd have a supply of the nitrate salt. The solution was colorless (no copper), but some small portion wouldn't dissolve.

I set this aside, washed and dried it, then tried again. No reaction. Any ideas for an element that would behave this way?


Did u filter the soln before adding Cu? if not then the ppt is probably from the contaminated Ag powder.

Bert - 16-4-2018 at 14:19

Did you notice the thread is 3 years old and the author has not signed in for 2 years?