Oxidation of Iron Filings in a Sealed Bottle

A couple of years ago I placed coarse iron powder in a sealed bottle to use in magnetism demonstrations. Recently I noticed that the bottle had partially collapsed and hypothesized that it the oxygen in the bottle's air had oxidized the iron to produce iron oxide. I used the volume displacement method (a large graduated cylinder partially filled with water) to estimate the gas volume in the collapsed bottle (405 mL) and in the bottle after allowing air to refill the bottle (490 mL). This represents a percent gas volume change of 17%, which is in the ballpark of the typical 21% oxygen concentration for air.

See: Campbell, D. J.; Bannon, S. J.; Gunter, M. M. J. Chem. Educ., 2011, 88, 784-785.

 

ABOVE: (LEFT) Partially collapsed bottle containing iron powder. (RIGHT) Reinflated bottle containing iron powder.