Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: bigblock on 01/10/2012 20:49:03

Title: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: bigblock on 01/10/2012 20:49:03

Just wondering if I will ruin my PTFE coated stir bar if used in hot Aqua Regia

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: damocles on 02/10/2012 12:01:02

It should be just fine (but I will not take responsibility if it is not [;)])

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: damocles on 02/10/2012 12:05:01

A pyrex encased magnet might be cheaper and less of a worry. (Put a small rod magnet in a glass tube where it is a fairly snug fit, and either seal both ends with a cutting flame or get your local friendly glassblower to do it).

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: lightarrow on 02/10/2012 12:37:47

Quote from: damocles on 02/10/2012 12:05:01

A pyrex encased magnet might be cheaper and less of a worry. (Put a small rod magnet in a glass tube where it is a fairly snug fit, and either seal both ends with a cutting flame or get your local friendly glassblower to do it).

This is interesting, but I imagine the metal/magnet bar shouldn't be tightly fitted or the different thermal expansion coefficient could break the glass when heated.

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: damocles on 02/10/2012 13:01:15

Yes lightarrow, that would certainly be a good idea. Magnet materials certainly expand more than pyrex, though neither expands much. I did not really mean 'tight' by 'snug', but perhaps it would be wise to be a little more conservative and specify 'an audible rattle' for the room temperature fit. When I was at Uni as a student in the 1960s teflon was a very expensive material, and most of the stirring rods in our teaching labs were home made glass ones of this sort.

Is bigblock wanting to dissolve platinum or something? (Gold goes quite happily in cold aqua regia; platinum is painfully slow, even in hot).

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: bigblock on 03/10/2012 02:05:20

Thanks for the information. I used it today in boiling aqua regia and it held up just fine. Yes Damocles, I am attempting to leach platinum grains. It looks like this will be very slow just as you said.

Title: Re: Can teflon coated stir bar be used in hot Aqua Regia?
Post by: lightarrow on 04/10/2012 20:09:24

Don't know but maybe Pt could be dissolved in melted NH₄HSO₄. I have no Pt to try with  [:)]