1. Warm-Up
List 5 features of genuine U.S. Currency that are not found on counterfeit currency.

2. Warm-Up (Answers) Inscribed security thread
Microprinting (ex: “United States of America” along portrait)
Off-center portrait
Watermark of figure
Optically variable ink (green to black)

3. Chromatography

4. Chromatography
Technique for separating and identifying components of mixtures
Determine chemical “fingerprint” of paints, dyes, inks
Dissolve dyes in liquid (water, alcohol, oils) and separate using chromatography paper
Calculating Rf factors can help determine the composition of substances

5. Relative Mobility Factor (Rf)
solvent front
color band A
origin
2.1 cm
2.8 cm
color band B = Rf
Distance ink band traveled
Distance solvent traveled
2.1
2.8
0.75

6. Lab: Chromatography of Ink
Scenario: A mysterious note was found on Mrs. Chou’s desk. It was written in black ink. Did someone use her favorite pen (a Uniball) to write the note?
Possible pens used: Papermate, Uniball, Sharpie, Pilot
Mystery pen = ???
Using alcohol as the solvent and by calculating Rf values, conduct a chromatography experiment to determine the pen used to write the note.

7. Procedures
Use a pencil to draw a line (1.5 cm from the bottom) across the filter paper.
Using each of the pens, draw a small dot on the line so that they are evenly spaced across. Use a pencil to label the dots.
Place a small amount of alcohol in the bottom of the beaker, just enough to cover the bottom.
Put the known and mystery strips of filter paper into the beaker. Wait until the alcohol has traveled almost all the way up the paper.
Remove from beaker. Draw a pencil line across the solvent line. Let dry. Calculate Rf values.

8. Experimental Setup

9. Data Table Pen Type Band # (bottom to top) Band Color
Band migration distance (mm)
Solvent Migration Distance (mm)
Rf Value (band/
solvent)
Pilot A B C
Uniball
(single)
Sharpie
PaperMate
*Unknown*

10. Analysis and Conclusions
Which pen was the unknown? Describe how you determined the identity of the unknown.
Besides alcohol, what other solvents do you think you can use to separate ink pigments?
What other applications do you think chromatography be used for?

11. Video: Crime 360
WHO: Who is involved in the crime scene investigation? Who are the victim(s) and suspect(s)?
WHAT: Describe the forensic evidence that is gathered.
WHERE: Where is the crime scene? Where do the CSI’s go during the case?
WHEN: Describe the time-frame of events. When does this all take place?
HOW: How do the CSI’s go about solving the case? What happens at the end?