CAS - Molecule of the Week

Molecule of the Week
September 18, 2006

This molecule was originally selected on November 17, 2003

Regarding this week’s selected substance:

An alkaline solution of thymolphthalein in alcohol makes a very good disappearing ink. The solution starts out blue, but when it absorbs carbon dioxide from the air, carbonic acid is formed, neutralizing the alkaline solution and causing the blue color to vanish. The color returns when the ink spot is treated with an alkaline solution.


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