The Bleaching Effect of Chlorine

We fed chlorine gas into a glass cylinder and a glass bottle, respectively. Chlorine gas is heavier than air, therefore we didn’t have to cover the glass to prevent the chlorine from escaping! The gas is slightly yellow and very aggressive.

Afterwards, we dipped a piece of filter paper into crystal violet (crystal violet is a purple liquid) and put it in the glass with the chlorine. Since chlorine bleaches colours, the violet colour vanished and a piece of white filter paper remained. We also put in filter paper that was coloured with various pens: One was labelled with a permanent marker, the other one with a text marker. We observed that all marked filter papers lost their colour except for the one with the permanent marker (bottom most picture, left glass bottle).

Likewise, we added different flower petals (red petals from a rose, blue petals from a bluebell and green leaves).

Our assistant, Christian, threw a whole rose in the cylinder, which turned yellow after some time (right glass bottle in the picture). However, the opinions differed as to whether the rose was yellow or colourless afterwards. After that, we put the bluebell in, which also lost its colour, as did the green leaf.