Sciencemadness Discussion Board

Help with indium chemistry

Booze - 23-4-2017 at 08:17

So I had some indium stuck in a beaker. I decided to dissolve it with nitric acid. I got impatient, so I added sodium hydroxide when it looked like no dissolving was happening. Then this white precipitate appeared. What is this, and how can I convert it back to indium metal?

elementcollector1 - 23-4-2017 at 08:26

Firstly, why would you add sodium hydroxide out of impatience? That just neutralizes the acid and makes dissolution slower, if not bringing it to a complete halt.

What you have now is most likely indium hydroxide and sodium nitrate in solution.

Booze - 23-4-2017 at 14:04

Quote: Originally posted by elementcollector1  
Firstly, why would you add sodium hydroxide out of impatience? That just neutralizes the acid and makes dissolution slower, if not bringing it to a complete halt.

What you have now is most likely indium hydroxide and sodium nitrate in solution.

I got bored and wanted to get rid of the acid.

fluorescence - 24-4-2017 at 07:01

I think much like Aluminium, Indium is quite passive against oxidizing acids, especially nitric acid. It also does not dissolve in NaOH solutions which is why not much happened. You could try HCl to dissolve it that should work better although I am not sure how well the Oxide or Hydroxide you formed already really dissolves in that. From the Chloride solution there should be a way back to the metal. I think there are demonstrations that form elemental indium.

Booze - 24-4-2017 at 08:58

Quote: Originally posted by fluorescence  
I think much like Aluminium, Indium is quite passive against oxidizing acids, especially nitric acid. It also does not dissolve in NaOH solutions which is why not much happened. You could try HCl to dissolve it that should work better although I am not sure how well the Oxide or Hydroxide you formed already really dissolves in that. From the Chloride solution there should be a way back to the metal. I think there are demonstrations that form elemental indium.


There was some indium oxide that was already there from melting it, and that dissolved just not the metal.

MrHomeScientist - 24-4-2017 at 09:30

Quote:
...I got impatient...
...I got bored...

This is not a good attitude to have in this hobby. Impulsive sudden changes to a reaction underway can lead to very dangerous situations. You have to be very careful and meticulous, and plan out everything before you do anything.

The white precipitate is very likely an oxide or hydroxide of indium, from a small amount of the metal that dissolved in the acid. Reducing it back to the metal probably won't be easy. It's less reactive than aluminum so a thermite-style reaction may work, but you'd need enough of the oxide to make at least a 50g batch (smaller thermites tend to be difficult to get going).

If you only wanted to get the indium out, just melt it again.

Melgar - 24-4-2017 at 14:55

Incidentally, HCl + H2O2 does a good job of dissolving indium. You'd likely have to wait a day or so though.

Actually, if you decant all of your liquid, then add HCl, then carefully added H2O2 when the reaction slowed (H2O2 can oxidize HCl into H2O and Cl2, which will come out of solution if there aren't enough other chloride ions present to keep it dissolved), you might still be able to salvage it.

[Edited on 4/24/17 by Melgar]