2. Some variables that could affect the different pigment bands is what type of marker was use, the what figures are drawn on the filter paper, how far away the dots are from the center, and how long the chromatogram is absorbing the water. The different types of makers could have different pigments which leave different color bands. The ink of the figures could spread more or less depending on the size of the figure. The distance between the center and the ink could change the spread if the filter paper has been saturated in water and the ink has not fully saturated. Finally if the chromatogram has only been absorbing water for a short amount of time the water might have parted the various inks.
3. The ink separates into different ink bands because different inks make up the black ink. Each are attracted to the paper in some ways, but some inks are much more strongly adsorbed than other inks as the water is absorbed up the paper, this creates rings of the different colored inks contained in black ink.
4. I chose the color blue which was present in what I could observe two types of ink. However they were not the same shade of blue. One was a dark blue that was toward the middle of a chromatogram, and the other was a lighter blue that was on the outside of a chromatogram. I will talk about the lighter blue. This blue from what I could discern was almost exclusively on the edge of the chromatograph. So, the pigment appears to always give the color in the same way. The pigment for the darker blue is most likely different because it was expressed by a different pen that from what I could see had no light blue ink. The marker that did have the light blue also had a ring of dark blue just below it, so they have to be different pigments because they are in different rings. The light blue pigment only appeared in one of the four markers we tested so it seems it is not a commonly used pigment in ink.
5. Water-soluble pens were only used in this activity because since it is water soluble. This means the black ink comes of in water, meaning the inks separate in water. "Permanent" markers which are more hydrophobic would have a harder time being separated by the water they are supposed to at least somewhat repel. I would modify the experiment by adding soap to the solute because "permanent" markers are much more soluble to soap and water than to water, so it would be easier to the pigment rings.
Links to research of ingredients of some ingredients in Sharpies
Diacetone alcohol http://www.inchem.org/documents/sids/sids/123422.pdf
Propyl alcohol http://www.inchem.org/documents/icsc/icsc/eics0553.htm
Butyl alcohol http://www.inchem.org/documents/icsc/icsc/eics0111.htm
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| Look at the blues in the ink rings |
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