Why does yellow move faster than blue?

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Offline krool1969

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Why does yellow move faster than blue?
« on: 01/02/2012 09:09:11 »
The other day I added green food color to clear liquid hand soap. As an exparment I didn't mix it but just stuck the pump back in which left a streak of dark green color. After an hour or two the color had defused somewhat into the soap but instead of green there was green surronded by yellow. I'm wondering why the yellow defused more quickly than the blue.

You can try this yourself. The soap is still usable so long as you don't add too much color (no more than 2 or 3 drops). Perhaps it could be a kitchen science?


Offline CliffordK

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Re: Why does yellow move faster than blue?
« Reply #1 on: 01/02/2012 16:48:39 »
You've discovered that different molecules can travel through a medium at different speeds.  This is essentially what is used in Column Chromatography to purify chemical substances in the lab.

Here is a listing of Types of food coloring.

There are a couple of types of blue, but Brilliant Blue is a very large molecule.

Sunset Yellow is a much smaller molecule.

Thus, one might expect the smaller yellow molecule to diffuse faster.

Sunset yellow may also be a bit more polar of a molecule, so that it would have a higher affinity for water, and thus move through a soap & water quicker than the blue.

It is possible that the blue would move quicker if you put it in vegetable oil or clean motor oil.