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How to Make Disappearing Ink

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How Disappearing Ink Works
Several color-change chemistry demonstrations use the same principle as disappearing ink.

Several color-change chemistry demonstrations use the same principle as disappearing ink.

Arne Pastoor, Getty Images
When the ink is sprayed onto a porous material the water in the ink reacts with carbon dioxide in the air to form carbonic acid. The carbonic acid then reacts with the sodium hydroxide in a neutralization reaction to form sodium carbonate. Neutralizaton of the base causes a color change of the indicator and the stain disappears:

Carbon dioxide in the air reacts with water to form carbonic acid:

CO2 + H2O → H2CO3

The neutralization reaction is sodium hydroxide + carbonic acid -> sodium carbonate + water:

2 Na(OH) + H2CO3 → Na2CO3 + 2 H2O

Let's make disappearing ink...

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