Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: dioxane on September 29, 2016, 06:11:31 AM
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Hi there!
I wanted to identify if the rust colored crumbles I recovered from cloth filters were rust so I soaked the filters in sulfuric acid and left them overnight. When I checked, the sulfuric acid turned greenish blue. I added some drops of KSCN and they turned red. I added around 2 mL of NaOH to another set and they either turned blue or purplish blue.
I attributed the greenish blue solution to the presence of Iron(II) sulfate since I used a relatively strong concentration of sulfuric acid while the resulting reaction with KSCN is the result of Iron(III) forming complex with the thiocyanate ion.
However, I cannot find the reason as to why the greenish blue solution turned blue / purplish blue when I added NaOH and so, I want to ask the reaction behind this. Also, since the reaction with sulfuric acid results in a mixture of Iron(II) and Iron(III), and given that Iron(II) sulfate is green solution while Iron(III) sulfate is brown, what color should the solution be in the first place?
I appreciate any in depth explanation for these observations.
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Perhaps what was filtered out is a mixture containing not only iron.
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I have a tub of iron (II) chloride that has partially oxidised (it's turning brown). One of the perils of trying to store chemicals in a hot and humid island country.
I put a spatula of it in some sodium hydroxide and I could see both the brown and green precipitates distinctly.
I think Borek is probably right, you have rust and something else.
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Incidentally, the Fe3+, SCN- reaction is one of my favourite Hallowe'en practicals to do with high school students.
A small amount of KSCN solution on the skin, drag a blunt knife dipped in FeCl3 solution along it, and it looks like you've been slashed...
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Always a crowd pleaser: https://www.youtube.com/watch?v=hqoCobAuAzo