Chromatography: A Means of Separation
The first thing bomb specialists do is collect the chemical
residue from the explosion site. In the case of a large explosion,
like the one at the World Trade Center, the residue can be found
all over the blast site. More often, it is only on the pieces of
the bomb itself.
Next, the residue is passed through a special material. The
material attracts some molecules more strongly than other
molecules. The molecules that are the least attracted separate
from the material the fastest; those that are the most attracted
take the longest to separate.
In the end, all like molecules line up together. This separation
process is known as adsorption.
Adsorption: An Analogy
Let's say you mix together sawdust and tiny pieces of metal, and
then pour them into a pile on a table. If you take a magnet and
slowly wave it back and forth over the pile, the metal pieces will
be attracted to the magnet and will stick to it. After a few
passes the pile will only contain sawdust, and the magnet will
hold all the metal. The reason this would happen is that sawdust
is not attracted by a magnet, but metal is. This gives you some
idea of how two different substances can be separated using a
special material that attracts one of the substances more strongly
than the other.
See for yourself:
Color Separator Activity
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