Chemistry 439 - Spring 2005
Fingerprinting

 Fingerprints can be observed and recorded in many ways. For some options, the pattern disappears within minutes after it appears. For these options, photographs work well for a permanent record. Basically, any method that allows you to observe a fingerprint is satisfactory. Students should attempt every method listed. For each option, prepare a set of 5 or more "standard prints" by getting your classmates to provide you with one of their prints. Develop the prints and note the differences. Then run the unknown to see if you can determine if it is one in your set of standards.

Option 1-Charcoal

    1. Place your finger on a hard surface
    2. Dust the print with charcoal and remove the excess
    3. Carefully roll a strip of clear tape (packing tape) over the fingerprint
    4. Remove the tape in one motion and apply to a sheet of paper using the same rolling motion to be sure you trap no air bubbles under the tape.
Option 2-Anthracene
    1. Place your finger on a hard surface
    2. Dust the spot with anthracene
    3. Carefully remove any excess anthracene
    4. Record your observations
    5. View the fingerprint with a UV lamp
    6. Record your observations
Option 3-Ninhydrin
    1. Place your finger on each end of two strips of paper about 4-5 inches long
    2. Spray two of the spots (on one strip) with a solution of ninhydrin (TLC desk)
    3. Place the paper strip in a folded paper towel and heat with an iron for a few minutes but do not burn.
    4. Remove the paper towel, observe the paper strip and record your observations.
    5. Cover one end of the strip of paper and spray the other end with 3% zinc chloride.
    6. Record your observations.
    7. Cover the end you sprayed with zinc and spray the other end with 3% nickel nitrate
    8. Record your observations.
Option 4-Cyanoacrylate fuming
    Look up a procedure online for performing cyanoacrylate (SuperGlue) fuming. This method is often preferred because it leaves a permanent record of the prints. A candle warmer is in lab to provide warmth to accelerate the process.
Report:
Include the options you selected and all of your observations and conclusions. Also include a complete description of how you compared the unknown fingerprint you tested (arches, loops and whorls) with your standards and the probability that an identification based on fingerprints may be incorrect. Include a copy of the actual fingerprints, if possible, in your report. If not possible, show the actual prints to the TA while they are available.