You just used the last of your breakfast cereal to make yourself a fresh bowl. After eating a couple of spoonfuls, you notice that the printing on the box claims that your cereal has the most metallic iron of any breakfast cereal on the planet. Now, your only sample of the breakfast cereal contains bran flakes, raisins, milk, and sugar. You decide to find out if the claim regarding the iron is true. How would you separate the mixture to collect the iron?

Question

aaronq · Answer

Precipitation gravimetry.. add a bunch of NaOH and filter the ppt

jfraser · Answer

if it's "metallic" iron, it's really just small filings of iron. Let the cereal sit in water for a couple of hours, stir it up well, and run a magnet around the outside of the bowl. The loose iron filings will be pulled out by the magnet

anonymous · Answer

Yes, this is a common demo, using a magnetic to pull the bits of reduced iron out of your cereal.  It may not be literally iron.  It could also be ferrous oxide (FeO), which is also magnetic.  The only reason I suspet this is because pure Fe powder might oxidize pretty rapidly to Fe2O3 (rust), and Fe+3 is poorly absorbed by the body.  Iron supplements typically provide the mineral as the Fe+2 salt, so maybe FeO is used here. It's hard to find out.