A Chemistry Lesson in Forest School

The children were really surprised to see the Bluebell (Hyacinthoides non-scripta) go pink when it was tapped on the top of the Yellow Meadow ants (Lasius flavus).

The ants will crawl over the offending flower (keep it tipped down and they should stay at the flower end) but more interestingly they will employ their secret weapon – a jet spray of formic acid (much like nettle stings and with similar effect on the skin).

Having by now most definitely attracted the attention of the ants you can just drop the bluebell onto the nest and watch what happens. Have a look at the photo at the top of this blog there is a photo of a Pinkbell with some ants on it.

The change from blue to pink might be a familiar one to many of you – it’s basically the litmus test. You may remember those rolls of blue paper we were forever dipping into conical flasks filled with inexplicable bubbling liquids that required you to wear plastic goggles and get your arm trapped in the fume cupboard. The blue in bluebell is an anthocyanin, water-soluble pigments well-known for exhibiting colour change when exposed to acids (or alkalis).

The formic acid squirted by the annoyed ants will gradually change your bluebell into a pinkbell. If you did a similar experiment with  Wood ants (whose latin name is Formica rufa) the chances are that the Bluebell would turn pink faster as wood ants are the largest species of Ant in the UK. They can grow up to 1cm long and they live in colonies that are like icebergs larger under the surface that you can see than on top.  If you are feeling brave you can place your hand gently on the surface of the nest (it won’t hurt) the wood ants will crawl on your arm spraying the formic acid. Once you have gently brushed the ants off if you smell your arm it smells a bit like salt and vinegar crisps.