Dissolving iron in HCl, unknown product

[mishima]

My class needed some iron (iii) chloride to determine the purity of some aspirin they synthesized, so I thought I might try making some. I left a strip of iron in concentrated HCl for a few nights under the fume hood. I was expecting a liquid with iron (ii) chloride to result, which would then gradually turn into iron (iii) chloride with time.

What I got was a light greenish snow-like solid substance accumulating in the bottom of the beaker (regrettably did not get any pictures). I filtered this off, but now I am wondering exactly what it was. Nothing went into the beaker but the 9 g Fe strip and about 100 ml of 12 M HCl.

The solution I ended up with performs like iron (iii) chloride, it will turn salicylic acid a purplish color. It is a very dark brown liquid that leaves yellowish trails on the sides of its container. I'm going to do a titration to get its exact concentration.

I should've had a bunch of excess HCl since Fe was limiting the reaction. Could I have saturated the solution with iron (ii) chloride?

 

[Borek]

According to wiki solubility at room temp. is around 70g/100 mL, and you are below 20g/100 mL. Then, you have a huge excess of Cl^-, so I wouldn't rule the precipitation out.

How pure was the iron?

 

[mishima]

It was a Flinn Scientific iron strip, which I believe are intended (or sold as) electrodes. I cut it up using snips. The package had been opened before, and some other pieces were showing very slight spots of rust. The one I cherry picked did not, though I did not look using magnification.

Additionally, this billowing solid was noticeable long before the strip had completely dissolved.

I will double check the packaging tomorrow morning, but I can't recall any quantitative indication of purity.

 

[pumila]

Sounds like you got ferrous chloride (tetrahydrate) at the bottom.

 

[LudusRex]

It is likely that the unknown product you obtained after dissolving iron in HCl is a mixture of iron (ii) chloride and iron (iii) chloride. The greenish snow-like solid is most likely iron (ii) chloride, while the dark brown liquid is a mixture of both iron (ii) and iron (iii) chloride. The yellowish trails on the sides of the container could be due to the presence of iron (iii) chloride, which has a yellow color.

It is possible that the excess HCl in the solution could have saturated the solution with iron (ii) chloride, resulting in the formation of both iron (ii) and iron (iii) chloride. This is supported by the fact that the solution performs like iron (iii) chloride and can turn salicylic acid a purplish color.

To determine the exact composition and concentration of the solution, a titration can be performed. This will help identify the amount of iron (ii) and iron (iii) chloride present in the solution.

In the future, it may be helpful to use a known amount of iron and a standardized concentration of HCl to ensure a more controlled and accurate reaction. Additionally, conducting the experiment in a controlled environment, such as a fume hood, can also help prevent any unwanted reactions or impurities.