A Spectrophotometric Analysis
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Reinforcing earlier density observations, we will determine the composition of a penny.


How much copper is there in a US Penny?

Remember the PENNY Weight vs. DATE plot you made at the beginning of this course.......................................... PLOT

You obtained information on a penny's composition based on its DENSITY.

This analysis will give you the exact per cent copper content.


  1. Making the STANDARD.
    • Obtain a computer assigned solid copper standard wire from the stockroom.
    • Weigh the solid standard on the Analytical Balance.
    • Dissolve standard in Concentrated Nitric Acid.
    • Neutralize solution with and add excess Ammonia.
    • Quantitatively transfer to a 100 mL Volumetric Flask.
    • Add ammonia, dilute to volume, stopper and mix thoroughly.
    a) Spectrophotometric measurement of the BLANK
    • Make a cuvet by marking a clean 10 cm. sample tube at the top.
    • Fill about 2/3 full with distilled water. Wipe free of dirt and fingerprints. This is the blank.
    • Set the spectrometer at 625 nm. This is yellow light.
    • Set the spectrometer for 0% and 100% T using the reference.
    • Measure and record the % T of the blank

    b) Standard 1........ 10.00 mL aliquot + ammonia diluted to 100.00 mL.
    c) Standard 2........ 20.00 mL aliquot + ammonia diluted to 100.00 mL.
    Analysis of the UNKNOWN copper solution.
    Analysis of the copper penny.

For more information see the following....

RWK 1997