Sciencemadness Discussion Board

Iron and Nitric acid - Nothing?

CHRIS25 - 12-5-2012 at 03:57

5.6 grams of cast iron cut up into pieces no larger than 1/4 cm in a beaker and 89.3 ml of 30% nitric acid added. I was expecting toxic brown fumes and the Iron to dissolve. Two hours later, a slight subtle discolouration to the solution (It is a kind of Silvery very subtle light Lime green colour and that's it. What on earth is wrong here?

The Iron came from my local supply - the beach. It is Cast iron, not steel, cutting it reveales that clearly. It is also brittle no tolerance to a hammer another sign that it is cast Iron. the Iron was also free from rust, except that it has a black discolouration to it, however I washed and brushed with steel brush first. I can only assume that it must be the Iron, not the acid, but this makes no sense.


[Edited on 12-5-2012 by CHRIS25]

weiming1998 - 12-5-2012 at 04:43

Quote: Originally posted by CHRIS25  
5.6 grams of cast iron cut up into pieces no larger than 1/4 cm in a beaker and 89.3 ml of 30% nitric acid added. I was expecting toxic brown fumes and the Iron to dissolve. Two hours later, a slight subtle discolouration to the solution (It is a kind of Silvery very subtle light Lime green colour and that's it. What on earth is wrong here?

The Iron came from my local supply - the beach. It is Cast iron, not steel, cutting it reveales that clearly. It is also brittle no tolerance to a hammer another sign that it is cast Iron. the Iron was also free from rust, except that it has a black discolouration to it, however I washed and brushed with steel brush first. I can only assume that it must be the Iron, not the acid, but this makes no sense.


[Edited on 12-5-2012 by CHRIS25]


Heat the beaker of acid+iron mildly in a water bath or a gentle flame. It should dissolve. If it still doesn't dissolve, something might be wrong with your acid. What is your source of acid?

CHRIS25 - 12-5-2012 at 05:36

Hi Welming. I was a bit afraid to heat it to be honest, I read some nasty stories. I got the acid from a Northern Ireland company but was told here on the thread not to mention company names? I read that Iron passivates and the oxide prevents the Iron from Dissloving, but continued with the experiment because I learned that by using dilute nitric acid would be perfect. I also read that adding copper and zinc will have the same effect as heating it but I do not have any way of getting hold of zinc. I placed the beaker in hot sand outside where it is warm, but maybe I should now place the beaker in some very warm water at say 50c?


Ok It's dissolving very slowly the solution is now turning brown, It's in a stainless steel teapot with hot water at 50c. I am making Iron nitrate and so the Iron nitrate is in solution I understand.

[Edited on 12-5-2012 by CHRIS25]

weiming1998 - 12-5-2012 at 06:02

Quote: Originally posted by CHRIS25  
Hi Welming. I was a bit afraid to heat it to be honest, I read some nasty stories. I got the acid from a Northern Ireland company but was told here on the thread not to mention company names? I read that Iron passivates and the oxide prevents the Iron from Dissloving, but continued with the experiment because I learned that by using dilute nitric acid would be perfect. I also read that adding copper and zinc will have the same effect as heating it but I do not have any way of getting hold of zinc. I placed the beaker in hot sand outside where it is warm, but maybe I should now place the beaker in some very warm water at say 50c?


Ok It's dissolving very slowly the solution is now turning brown, It's in a stainless steel teapot with hot water at 50c. I am making Iron nitrate and so the Iron nitrate is in solution I understand.

[Edited on 12-5-2012 by CHRIS25]


If your kitchen extractor hood works, use that and open all windows, and watch the amount of NO2 coming out, if you smell too much, immediately turn off the heat and take the pot outside. NO2 is poisonous, but not so poisonous a whiff can kill you. If the extractor hood does not work, get warm water/a camping stove and slowly heat the solution outside.

CHRIS25 - 12-5-2012 at 06:14

No I have to do it outside, my wife is cooking! But the extractor fan is not that efficient to be honest in that smoke from normal cooking still manages to woft its way through the kitchen. I will heat teapot with camp stove, can you basically heat too much, obviously not going to boil it.

CHRIS25 - 12-5-2012 at 06:38

Hi Welming, heat the solution to what though? I have no idea how dangerous this can be. I decided to turn it off because I really can not find any info on the web about how to heat. All this maths and stoichemetry is fine in theory, but the practical side of things is hard to discover on the web at least with this particular reaction I have found only one school you tube demo so you can imagine what that is like!

hissingnoise - 12-5-2012 at 06:49

Quote:
I got the acid from a Northern Ireland company but was told here on the thread not to mention company names?

Chris, what concentration was the acid you got ─ I'd assume 68% rather than fuming?

CHRIS25 - 12-5-2012 at 06:56

Hi, I could only buy 30%.

weiming1998 - 14-5-2012 at 00:04

Quote: Originally posted by CHRIS25  
Hi Welming, heat the solution to what though? I have no idea how dangerous this can be. I decided to turn it off because I really can not find any info on the web about how to heat. All this maths and stoichemetry is fine in theory, but the practical side of things is hard to discover on the web at least with this particular reaction I have found only one school you tube demo so you can imagine what that is like!


You can place your container with the iron and nitric acid inside a larger, heat-resistant container, then slowly heat with a camping stove or a home made methylated spirits burner if you don't have a proper lab Bunsen burner/hotplate. If it still doesn't dissolve at an appreciable rate, take your nitric acid+iron container out and heat it directly with the burner (through a layer of something, like a sheet of iron, to disperse the heat a bit so you don't crack a glass container). Only heat like this if you have proper borosilicate glassware or it will crack! If done outside, the amount of nitrogen dioxide shouldn't be much of an issue.

CHRIS25 - 14-5-2012 at 02:45

I have placed the Borosillicate beaker inside a thin stainless steel holder and this is suspended by an iron holder above a methylated spirit burner. This is safe right? I don't have anything that is heat resistant and if it is heat resistant I don't get how you can heat it? Obviously have misunderstood the image that you have in your head, comes accross as a different image in my head but can't quite grasp what you mean. Anyway my first suggestion should be ok. I know that nitogen dioxide is lethal but it should not react with stainless steel should it? Am doing this outside inside a chimney stove/boiler flume made of highly heat resistant metal, obviously only saying latter so you know what kind of metal it is.

weiming1998 - 14-5-2012 at 02:53

Oh sorry, I meant the outside steel container should be filled with water first. If the container holding the beaker is filled with water, without the water going into the beaker, then it's safe to heat it. Basically, a water bath. Also, no chimney is needed. Simply doing this outside is safe enough.

Waffles SS - 14-5-2012 at 05:20

I did this reactions 1 years ago several times.I tried Fe2O3 and Iron metal,I have to say that Iron(III)Oxide is really stable and doesnt react with Sulfuric acid or Nitric acid and even Hydrochloric acid but Iron metal easily react with 55% Nitric acid and produce Fe(II)Nitrate and lot of F**king NO2.

At first Iron(II)Nitrate and then it oxidize to Iron(III)Nitrate.You have to know that Iron(III)Nitrate will oxidize to Iron(III)Oxide by air oxygen and you should do this reaction under vacuum or under inert gas.

Best equipment for this purpose is Water Jet.it wil make vacuum and also it will eliminate NO2 by dissolving it in water(10% NaOH solution will work better)



[Edited on 14-5-2012 by Waffles SS]

CHRIS25 - 14-5-2012 at 09:35

Thanks waffles. I just posted my end result of this whole reaction on the other thread about Ferric nitrate, not too sure where to go from here. Hope I don't get into trouble. I am taking notes about what everyone is saying. I can not do this reaction under inert gas or vacuum, just outside, I will look up what water jet is though.

So I assume that I have a solution of Iron Oxide then, not nitrate? Never been so darn confused about all this. The equation balancing does not give this though, and the material that I have read never suggests that it is not possible to get Ferric nitrate.

[Edited on 14-5-2012 by CHRIS25]