::FUN CHEMISTRY FACT OF THE DAY, PART 5::
On with my affinity for the chemistry of color and light!Chromatography
involves the separation of complex mixtures. Ecologists perform chromatograms on air samples to see what gases make them up. Detectives (chemical
detectives!) use chromatography to match pen types used in ransom notes. The funnest (and most see-it-yourself) version uses paper or fibrous material to "seep" various colors of ink from a pen.
Imagine you're using a black felt-tip pen to write a note. You're actually using about four colors blended together. By using chromatography (chroma
= color; graphy
= representation), you can get the inks, due to "the differential affinities of substances for a stationary adsorbing medium through which they pass" (basically, how "willing" they are to seep through a piece of filter paper), to make a little rainbow "fingerprint" exclusive to that pen. Try it
What do you think would happen if you used a Sharpie (or other permanent marker) in that experiment?
(Chromatographic answer in the comments.)