Lab 3: Chromatography
1. Why is it important that only the wick and not the filter paper circle be in contact with the water in the cup?
It is important for only the wick and not the filter paper circle to touch the water in the cup because the wick allows the water to spread slowly across the paper and thereby allow the pigment to spread over a greater span of time. By using a wick to draw up water, water can spread from one area outward from the center to the edge of the paper and thus create a pattern; if it was placed directly into the cup of water no such effect could be produced.
4. Choose one color (e.g. yellow, red, or blue) that is present in more than one type of ink. Is the pigment (compound) that gives this color always the same? Do any of the pens appear to contain common pigments? Explain.
Since we experimented only with black pens, it is difficult to confirm if particular colors span across several types and colors of pens. However, based upon our observations the color yellow appeared frequently amongst the black pens even though other colors such as green or red did not appear in every chromatography. However, it does not always appear in the same shade or intensity; in one experiment the marker yielded a soft, pastel shade of yellow while in another it yielded a strong, almost neon yellow color.
It is important for only the wick and not the filter paper circle to touch the water in the cup because the wick allows the water to spread slowly across the paper and thereby allow the pigment to spread over a greater span of time. By using a wick to draw up water, water can spread from one area outward from the center to the edge of the paper and thus create a pattern; if it was placed directly into the cup of water no such effect could be produced.
2. What are some of the variables that will affect the pattern of colors produced on the filter paper?
The pattern of colors produced on the filler paper are affected by factors such as the shape and location of the pen mark, the type of pen (ink pen, marker, etc.), and the composition of the ink; different brands of pens differed in chromatography even if the ink appeared the same because each brand tends to use a different recipe and ratio when it comes to inks.
The pattern of colors produced on the filler paper are affected by factors such as the shape and location of the pen mark, the type of pen (ink pen, marker, etc.), and the composition of the ink; different brands of pens differed in chromatography even if the ink appeared the same because each brand tends to use a different recipe and ratio when it comes to inks.
3. Why does each ink separate into different pigment bands?
Each ink separates into different pigment bands because the individual pigments within the inks have different levels of solubility. The substances that dissolve readily and quickly into the water spread farther up along the paper while those that had a lower solubility were absorbed by the paper more strongly than the ones with a higher solubility. The differing levels of solubility of the individual components of ink are what cause these bands to form.
Each ink separates into different pigment bands because the individual pigments within the inks have different levels of solubility. The substances that dissolve readily and quickly into the water spread farther up along the paper while those that had a lower solubility were absorbed by the paper more strongly than the ones with a higher solubility. The differing levels of solubility of the individual components of ink are what cause these bands to form.
Since we experimented only with black pens, it is difficult to confirm if particular colors span across several types and colors of pens. However, based upon our observations the color yellow appeared frequently amongst the black pens even though other colors such as green or red did not appear in every chromatography. However, it does not always appear in the same shade or intensity; in one experiment the marker yielded a soft, pastel shade of yellow while in another it yielded a strong, almost neon yellow color.
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?
Only water-soluble markers or pens are used in this activity because in order for the water to carry the pigments across the paper, they must be able to dissolve in water and thus be transferred. Therefore, this experiment will only be compatible with inks that dissolve and spread once in contact with water. Therefore, in order for a chromatography to succeed with pens that contain ink that is not water soluble, water must be substituted with a substance that will lift the ink off of the paper and spread it further out. Thus, I believe that alcohol or nail polish remover would be a suitable substitute for water because it is a colorless liquid like water and it is able to dissolve and lift permanent markers and other such inks.
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