Why does it smell so bad?

This is not directly IB related but it is certainly Chemistry related.

I was carrying out the reaction between iron filings and hydrochloric acid yesterday. An experiment I am sure many others out there have carried out. The context is the reactivity series and it also involved reacting magnesium, aluminium, copper and zinc with hydrochloric acid. I have carried out these reactions many times in many different schools and continents and always get the same puzzling result.

The iron reacts (fine) butr also produces a very smelly gas – I suspect it is hydrogen sulfide – but if it is, where does the sulfur come from. Is it simply that the iron contains sulfur impurities or is there a more sinister reaction at work?

Answers (if you know or just if you think you know) below please!

  • Nate K.
    September 27, 2012

    I don’t teach IB Chem, but I’ve wondered this for years, and it seems hard to get a straight answer.

    Manganese(II) sulfide is apparently used in steel production as an inclusion to increase strength. But why does just plain iron give off this stinky gas?


    This article explains that pyrite briquettes (FeS2) can be added in cast iron manufacturing.

    I’m guessing that if the iron you’re using isn’t “reagent grade”, there are probably sulfur impurities. I don’t know about you, but the “iron filings” we use in our chemistry lab might have been ordered by people whose grandchildren have died of old age.

    • David
      September 27, 2012

      Thanks for this Nate K – it makes perfect sense – I’ll pass this gem onto my students

Leave a Reply

Your email address will not be published. Required fields are marked *