The compound is prepared by treating iron metal powder with nitric acid.
This is from wicki.
2 Fe + 8 HNO3 = 2 Fe(NO3)3 + 2 NO + 4 H2O.
i Put 28g of iron filings in a beaker with 135ml of HNO3 and nothing happens. is it because iron filings are to coarse or do I need some kind of
catalyst to get the reaction going? heat maybe? or is this not possible at all.DraconicAcid - 10-4-2013 at 11:07
How concentrated is the acid? Sometimes strong nitric acid will passivate the metal surface, and prevent it from reacting.
Alternatively, how clean were the iron filings? If they were at all greasy or oily, the oil will prevent the acid from reaching the metal surface.Steve_hi - 10-4-2013 at 11:14
Sorry the acid is 68% Tech grade rated 15M
The filings were purchased from I think home science tools so they should be clean. So if the acid is too concentrated can I add a little water at a
time to dilute it?elementcollector1 - 10-4-2013 at 11:21
Dilute it in about half and you should get a result. Alternatively, see if it reacts with copper - that should give you some idea of the passivation
going on (no reaction = too concentrated).Steve_hi - 10-4-2013 at 11:28
If you look in the dryng copper nitrate thread you can see the results of my nitric acid on copper wire I had a very strong reaction instantly with
lots of NO2 evolving very quickley but Would the fact that Iron is more dense than copper require an more concentrated acid Ill add a little water to
begin with to see if that works. nezza - 10-4-2013 at 11:40
It probably is due to passivation. The HNO3 oxidises the Iron to a resistant oxide which prevents further attack. Try diluting the Nitric acid as
elementcollector suggested.Steve_hi - 10-4-2013 at 11:40
Thanks guys
I decanted the acid into another beaker and added some wate to what was mostly iron filings after about 20 seconds there was a violent reaction almost
like a volcano. Ive added more acid and just waiting for it to calm down some before adding more.
seems counter intuitive that something more dense like iron would require a less concentrated acid but a nice lesson in more isn't always better.DraconicAcid - 10-4-2013 at 11:41
Copper reacts very nicely with concentrated nitric acid- it is not passivated. Iron, on the other hand, may be. Try adding a small amount of water,
a bit at a time. It can get exothermic (not as bad as sulphuric), so don't dump a whole bunch in at once.
The density of the metal has no correlation with the density of the acid needed to react with it.DraconicAcid - 10-4-2013 at 11:44
seems counter intuitive that something more dense like iron would require a less concentrated acid but a nice lesson in more isn't always better.
The density and hardness of a metal do not correlate with their reactivity. Mercury is much more dense and softer than iron or copper, but is much
less reactive. Lead is softer and more dense than copper or silver, but is much more reactive than either of them.
And copper is more dense than iron.Steve_hi - 10-4-2013 at 13:10
Okay thanks again i said that without knowing or looking at the periodic table Just with my expierience as a machinist that copper has always been
softer than Iron I just remember reading to day on wickapedia that iron IS actually soft in its pure form but the iron Ive always worked with has
impuities in it which makes it hard. So much to learn and so little time to learn it in. Again thank you everyone.DraconicAcid - 10-4-2013 at 13:17
Okay thanks again i said that without knowing or looking at the periodic table Just with my expierience as a machinist that copper has always been
softer than Iron I just remember reading to day on wickapedia that iron IS actually soft in its pure form but the iron Ive always worked with has
impuities in it which makes it hard. So much to learn and so little time to learn it in. Again thank you everyone.
Anytime- most of us are founts of information (and some of us are reluctant to shut up. Okay, *I* am, at least).
Hardness and density aren't correlated, either. Platinum is harder than gold, but more dense; gold is softer than most metals, but still more dense
than most.binaryclock - 11-4-2013 at 06:26
Want to see what happens when you have a very concentrated nitric acid solution? It doesn't cause a reaction unless you dilute it. In this youtube
video you can see what others are talking about :
I read in an old reference that HNO3 and Fe is a very unimpressive reaction. Similar to the reaction of Arsenic and HNO3, I would guess. However,
adding a little HCl apparently makes the As dissolve more rapidly in the HNO3. So perhaps adding a small amount of an acid capable of attacking the
passivation layer, may potentially improve the direct Fe and HNO3 approach. Assuming the passivation is due to FeO, I would try adding a little HOCl
or even Acetic acid to the HNO3.
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I like the video and the NO2 approach to HNO3, where NO is created from HCl, a nitrate and Copper, and further reacted with O2 for NO2. I am thinking
about a SO3 preparation per the reaction NO2 + SO2 --> SO3 + NO. The reaction obviously requires NO2 also, and is exothermic (after it is started)
and the products are dangerous to say the least.
[Edited on 21-5-2013 by AJKOER]vmelkon - 20-5-2013 at 19:20
