Forensics Chemistry project

Forensics Chemistry project - strips using a different...

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Who Wrote It? Chromatography is used to identify different inks. Say someone committed a crime by changing the dollar amount on a check. Using chromatography, an investigator could tell whether more than one ink pen was used to write on the check and whether the suspect's ink pen could have been used. How does it work? Well, ink is not really made up of one color: there are actually different pigments making up one ink. In chromatography, the ink is soaked in a solution so that the different pigments will "bleed" apart and the true colors be revealed. (As you might guess, there is a drawback: the evidence is destroyed in the process.) You can see how chromatography works by doing this experiment. Fill a tall glass half way with water. Cut 3-4 strips of filter paper or of a heavy paper towel and attach the ends to a stiff piece of wire or a stick that can rest over the top of the glass. Next, make a large dot of ink about 1/2 an inch from the bottom of the
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Unformatted text preview: strips, using a different brand of black marker, felt-tip pen, or ink pen for each strip. Set the strips in the glass so that the ends touch the water but the ink dots are above the water level. As the water soaks up into the paper, the ink will begin to separate into different colors. Note that some inks are not water-soluble; if the ink does not bleed, try using either nail polish remover or rubbing alcohol (stronger solvents that can dissolve the bonds in the ink) instead of water. You can also look at "suspect" paper itself - are there watermarks or imprints from writing on top? Professionals also study handwriting and can analyze a sample of disguised writing to see if it has characteristics that match a suspect's normal writing.
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