What is the chemical formula for invisible ink?

Answer 1

"Method One
The simplest method is to use lemon or onion juice to write with and let it dry. To reveal the writing, heat the paper with a iron, or other heat source.

Method Two
A more sophisticated approach uses an acid or base to write with and a pH indicator to reveal the writing. (pH is a measure of how acidic or alkaline a substance is - a pH of 1 is extremely acidic, 7 is neutral, and 14 is extremely alkaline). pH indicators change colour when mixed with acidic or alkaline substances.

To write with: White vinegar (which contains acetic acid) is probably the most convenient source of an acidic 'ink'. To make an alkaline 'ink' try a mixture of baking soda and water (around 50/50). With a small paint brush, write on a piece of paper using your chosen 'ink' and allow it to dry.

To reveal the writing:There is a natural pH indicator (a pigment called flavin) found in apple skin, grapes and red cabbage (amongst other things). Boil half a red cabbage in 5 cups of water. Filter out the cabbage, and spray or paint the juice over your invisible writing. I tried doing this with apple skin (I imagine this is only red apples), which also worked.

If you just want to see the pH indicator working, put a little of your cabbage/apple juice in the bottom of a glass and note the colour. Now add some white vinegar, noticing the colour change. Next add some baking soda. You will see the colour change back again. Enjoy :-) "

Answer 2

like milk and lemon juice if you wrote something you dry it and when you take a lamp and shine on the paper the ink (milk or lemon juice) will become visible

I use ONION JUICE perfectly well...!

Answer 3

well it depends on what you mean by acid because invisible ink can be made out of a lot of things like baking soda lemon juce or anything citrus like milk urine all kinds of things

Answer 4

The chemical reaction is:
2 C6H8O7 + 3 CaCO3 = Ca3(C6H5O7)2 + 3 CO2 + 3H2O

Answer 5

It's Just Lemon!

Answer 6

CoCl2.6H2O