Fellow members,

 

I ask for your help- I add nitric conc to Fe powder slowly. It dissolves after a while, and after cooling/settling, I get most of the Fe to dissolve to clear solution as well as a bunch of ppt (oxidized Fe?). I am trying to first, get all of it to dissolve without the brownish oxide, and second, to get ferric, not ferrous nitrate. Should I use any water anywhere?

 

I can use either one, but prefer ferric. I know now, that there are some pretty sharp guys here, so I am confident I can get some good advice, eh??

 

Thanks!!

 

Oh, in the end, I prefer the hexahydrate, but nona hydrate is OK too.

Edited April 3, 201213 yr by pippo

My advice is to use a Fe(III) compound instead of the metal. Fe(OH)3 comes to mind. The leftovers are probably being slowly dissolved by the nitric acid, but there may not be enough (try heating to make it more active).

As for hydration, certain temperatures can give certain hydrates. If you start with the nonahydrate, and heat it to decompose it, it should form either the anhydrate or the hexahydrate. This chemical is deliquescent, so store it away from water.

This is guesswork, I have no idea how this will play out in real experimentation.

If there's enough nitric acid and enough time the iron will be oxidised to Fe(III) but there will be a lot of NOx generated which isn't nice stuff.

 

Also, unless the solution is strongly acid the hydrated Fe(III) ions will tend to form basic species which are a brown colour rather than the violet colour of the hexaquo ion.

Thanks, John, and element (sorry for long delay- out of town for 2 weeks). Good tips. Thing is, I have the Fe powder, and want to take advantage of it. It is pretty pure stuff. Not woried about NO2 fumes- no big deal- I work with metals all the time. Now, John, you warn about the basic Fe product which Ive seen before. youre right- it is yukky stuff,, and useless, and unwanted. In your opinion, could this occur if/when I introduce some water to the mix?

 

If so, Should I just stick with addn of pure nitric to the Fe and give it time to dissolve?

 

Thanks.