The Blue Bottle Experiment Revisited: How Much Oxygen?

To prove that oxygen is irreversibly consumed in the blue bottle reaction, a manometer or a plastic bottle was used to show a permanent reduction in the gas pressure in a reaction vessel. This demonstration may be misleading because the change in gas pressure can be attributed to a number of other factors such as temperature change and involvement of other gases. More importantly, the use of a plastic bottle should be discontinued because of safety and environmental concerns. An inexpensive hand-held oxygen gas probe is employed instead to provide conclusive proof of irreversible oxygen consumption. The new procedure can also help reveal the role of the redox dye that was previously assumed to be a catalyst for all variations of the blue bottle reaction. Our improved procedure shows that, unlike sugar reducing (in classical version of the blue bottle reaction), benzoin and vitamin C (in rapid and green versions of the blue bottle reaction) undergo autoxidation at noticeable rates without the dye.