Demonstrations

The disappearing rainbow¹ is a wonderful chemistry demonstration previously featured here on ChemEdX.^2-4 In this experiment, a colorless solution of NaOH is poured into a row of flasks, each containing a different acid–base indicator.

Dean Campbell*, Ali Patel, Kathryn Campbell *Bradley University, Peoria, Illinois

The Density Bottle experiment has inspired many colorful variations over the years.^1-6 I recently came across yet another colorful variation that I’d like to discuss.

Josh Kenney, Melissa Hemling, and I just published an article in the October 2024 Journal of Chemical Education. The article describes inquiry-based activities that highlight the chemistry behind “No-Mess” picture-coloring books.¹ Well, it turns out that our timing is impeccable.

Galinstan is the tradename for a liquid metal alloy that is comprised of three elements: gallium (68.5%), indium (21.5%), and tin (10%).¹ It behaves a lot like mercury but has significantly lower toxicity. Because of this, Galinstan is used as a replacement for mercury in a variety of applications.

A variety of interesting coloring books are available on the market that use water as a coloring agent.¹ When water is applied to the pages of these books, colors seem to appear like magic. When the water evaporates, the colors disappear. This allows the pages of these books to be colored over and over again.

In “salting out” demonstrations, a mixture of water and an organic liquid separates into two layers upon addition of an inorganic salt.^1-4 Typically, acetone or various alcohols are used for the organic liquid, while NaCl, Na₂CO₃, or K₂CO₃ are used as the salt.

About a decade ago, I wrote briefly about the interesting experiment of throwing boiling hot water into air that is below -18°C (0°F) (see Ice Clouds).

Co-Authored by Dean J. Campbell* and Ali Patel* *Bradley University, Peoria, Illinois