Should water come in contact with the filter paper, then the ink and water may not spread out from the center to the edges, and therefore not create the radial pattern that did result from this lab.
2. What are some of the variables that will affect the pattern of colors produced on the filter paper?
Different inks resulted in different colors; for example, LiquidFlair resulted in only black, but the thin Expo marker created bright shades of blue. Other variables included the pattern drawn in the center. The longer it was vertically, the farther the water and ink ran outwards. Of course, this also includes the amount of ink on the paper. When I used a thick Mr. Sketch marker and drew bold lines, the ink spread very far, versus when I put a circle of tiny dots, which just spread a little. The distance from the center also made an impact, because the ink spread outwards only, and not inwards.
3. Why does each ink separate into different pigment bands?
Chromatography is defined as "the separation of a mixture by passing it in solution... through a medium in which the components move at different rates." As the focus of our lab today was on this, we separated a mixture through a medium. The mixture was the ink, and the medium was, of course, the water. When the water reached the ink and passed through it, it separated the ink into the different pigments that made it up; in other words, it divided the homogenous mixure that was the ink into all of its different components, or pigments. This resulted in bands of these pigments. Each color pigment is unique in its physical properties; these differences show in their ability to travel further or not as far on the filter paper. One property would be its water solubility; if the pigment is highly water soluble, it will "float," or remain in the water for longer, and therefore travel more. If its water solubility is not high, it will not stay in the water for long, and will create a pattern closer to the center.
4. Choose one color that is present in more than one type of ink. Is the pigment that gives this color always the same? Do any of the pens appear to contain common pigments? Explain.
Blue appeared in many different inks, in different forms. For exmple, we had purple on one filter paper, which is just red and blue, and blue by itself in another. Green, a mixture of blue and yellow, was also present in another pen's ink. As such, we can say that blue was present in more than one type of ink. The pigment that gives this color is not always the same; at one point one chromatogram had dark blue on it, but another had a cyan blue color. I did not see any pens that appeared to contain common pigments.
5. Why are only water-soluble markers or pens used in this activity? How could the experiment be modified to separate the pigments in "permanent" markers or pens?
Water-soluble markers and pens were the only ones used in this activity because this property allowed the ink to be separated and carried by the water to spread and create patterns. Had permanent markers been used, the pigments would not have separated and created pigment bands, and as such the experiment would have failed. A good example of this was Nina's chromatogram, in which she'd accidentally used a not water-soluble pen to draw on it. About twenty minutes later, the water-soluble pens she'd used had successfully spread, but the lines drawn by the non-water-soluble had not changed. To separate the pigments in "permanent" markers or pens, it would be best to switch the medium to something that the ink in the "permanent" markers could be separated by; in other words, water should be swapped for something this specific ink is soluble in.
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