Chromatography Methods

The theory of chromatography is simple: you dab a dot of color onto a paper, stand the paper up in water, and let the rising water separate the colors by solubility.  But how do you make sure the paper stays upright?

One easy method is to crease the chromatography paper vertically, then stand it in water.  This works especially well if the bottom of the paper is cut flat (an angled bottom will make the paper tip.)

If the paper doesn't stand on its own, try folding the top of the paper over the side of the glass.  Note that that this method is problematic: a professional biochemist cautioned me that surface tension between the glass and the paper might interfere with the capillary action causing the water to rise.  However, it works well enough for M&M color separation, or the other basic chromatography we do in our kitchen.  For better results, angle the bottom of the paper out so that the paper is not stuck to the glass.

If your chromatography paper is especially difficult to work with, clip it in place with clothespins or binder clips.  Lay a pencil over the top of the glass and clip on the paper, forming a T with the paper hanging down, or take a shortcut and clip it to the side of the glass, as shown (angling the paper out from the glass, as above).

When doing chromatography with large groups, I use clothespins on a wire rack to suspend the chromatography papers over a dish of water.  This way I only need one water container.  (Make sure your scientists label their papers in pencil if they want to know which are theirs.)

Whatever chromatography method you use, make sure that the color dot is placed above the waterline.  This is easy if you're hanging the paper--just hold the bottom edge in the water with the dot above the surface, then clip the paper in place.  If you fold and stand your paper, make sure the dot is high enough so that it will still be dry when you stand up your paper.  Then watch the water rise, and see what colors your dot is really made of.

CakeMate Hearts

If you're not making cupcakes, there's only so much you can do with Cake Mate Valentine's hearts.  After we had eaten our fill of the hearts a kind neighbor gave us, I wondered what we'd do with the rest.  "How about candy experiments?" a friend suggested.  Of course.

According to the label, these red hearts actually contain three dyes: Red 3, Red 40, and Yellow 6.  When we tried chromatography, the red heart dye separated into at least two different colors, a pink and an orange.

If the color table on www.red40.com is accurate, we found Red 3 ("cherry-red") and Red 40 ("orange-red").  Yellow may have been too faint for us to see (this is common), it might not separate from the other dyes in water (for instance, if it moves at the same speed in water as one of the other dyes), or it may only have been used in the pink candy which we did not test.

We also wondered if the hearts would sink or float.  Turns out they do both.

These two hearts were put in water at the same time.  One sank quickly, while the other floated for several minutes.  The floating heart had an air bubble trapped underneath, which probably helped the buoyancy.

Overall, the hearts floated at first, then sank, then returned to the surface as a dissolving mass of bubbles.

Jelly Belly Beans

I got an email from a mom planning a Jelly Belly birthday party. Did I have any ideas for Jelly Belly experiments? I rushed out to buy a bag; here are my suggestions:

1) Floating Letters
The Jelly Belly logos float, just like M&M m's and Skittles s's. Leave the jelly beans in water, logo side up, for a few minutes and see if the logos peel off. The warmer the water, the faster it goes.

2) Chromotography
Jelly Belly chromatography should be really fun, but since I had to use paper towels (I'm out of coffee filter paper) I didn't get the best results. Green Apple separated nicely into blue and yellow, and the red-brown Dr. Pepper had a nice streak of red separate out from the rest of the dye. Black didn't separate with my materials, but I'll try it again with coffee filter paper, since we've had great luck with black jelly beans lately.

3) Acid Test
Regular Jelly Bellies, it turns out, are not very sour. Only dissolved Green Apple beans gave me any visible bubbles when I poured in the baking soda. I'll try it again when I can get some Jelly Belly Sours; I bet those'll work great.