Unit 8.3 Analyzing the Unknown
Students apply chemical principles to problem solving. Analytical
methods for analyzing solutions of unknown composition are
Video program cues: 16:00 28:00
"Everythings different. No case is
ever the same. I worked as an analytical chemist and everything
is routine, its the same, but in case work, theres
a lot more challenge, and trying to figure out something,
and it is satisfying when you make the connection between
the victim and the suspect, and its kind of neat when
you find something that nobody else ever thought of doing.
General unknowns are a lot of fun, too, because theyre
a big challenge: what is it, where did it come from, and
you try to identify a complete unknown, because it could
be anything in the world that could be used as evidence.
So, its always a big challenge. I like the puzzle,
the mystery of trying to figure the things out. Typically
what we do is we get a sample, and we take just a few grams
on the spatula, and we burn it. That would be a positive
flame test, because it goes with a flash, it does that hissing
sound, and it gives off a puff of white smoke. That would
be a characteristic of black powder. Some explosives also
burn but black powder has these distinctive burn characteristics
that people can identify
from the way it reacts with
the flame you can tell, and of course, under the microscope
they are very different."
FBI Explosives Unit
- This site describes the activities of the FBI
Chemistry Unit. Scroll to the bottom of the page and
click on "Handbook of Forensic Services" for
Identifying solutions laboratory
Felix Muhiga teaches about finding the chemical composition
of solutions by using a common test for ions.
- This site, from ChemSource,
gives a complete lab procedure for cation analysis.
The chemistry of DNA
"The foundation of DNA, when you go
to molecular biology or to molecular biochemistry, obviously
has its basic roots in chemistry. Acid-base relationships,
protein chemistry, all these kinds of things, which typically
are found in biochemistry but you still have to know acid-base
reactions and things like that, are from chemistry."
FBI DNA Unit II
Heinhorst, S.; Cannon, G. (2001)' Nature: "Green" Chemistry,
Natural Antioxidants, and a DNA-Fueled Machine, 'Journal
of Chemical Education, Vol. 78, No. 2, pp: 150-151.
to Unit 8.4