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Chemistry In Pictures

Chemistry in Pictures: Dyeing to learn chemistry

by Brianna Barbu
July 26, 2022

A student in a lab coat, goggles, and gloves holding up a tie dyed bandanna with a fume hood in the background.
Credit: Joseph Houck

The student holding this bandanna, Nathan Ouyang, made the dye to color the fabric himself in a lab at the US National Chemistry Olympiad Study Camp. Every June, the 20 top scorers on the National Chemistry Olympiad exam gather at the study camp to train for the International Chemistry Olympiad and vie for one of four spots on the official US team. Much of the camp involves studying for a 5-hour theoretical exam, but the students also get hands-on training in practical laboratory techniques, such as organic synthesis. This year, that involved synthesizing indigo . . . and then using the product for tie dye (once it was properly characterized, of course).

A scheme showing the chemical reduction of indigo to leucoindigo and the air oxidation of leucoindigo to indigo.

Indigo is not very soluble in water, but it can be chemically reduced with sodium hydrosulfite to make a water-soluble leucoindigo solution. It was this solution in which the students dipped their bandannas to dye them. Over time, the oxygen in the air converted the yellow-colored leucoindigo to brilliant blue indigo, giving the students a keepsake reminder of the beauty of chemistry.

Submitted by Joseph Houck

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