1. THE COMPOSITION OF PENNIES PRE-1982 AND POST-1982 Tim Cumming & Caitlin Carmody

2. Timeline of the Penny Composition pure Copper from 1793 to 1837 From 1837 to 1857, 95 % Cu, 5 % Sn and Zn In 1857, 88 % Cu, 12 % Ni 1864 to 1962, 95 % Cu, 5 % Sn and Zn In 1962, 95 % Cu and 5 % Zn In 1982, 97.5 % Zn and 2.5 % Cu

3. Why did the composition change? The value of Copper increased (almost double) making the government lose money when they produced pennies Zinc was, and still is, the most economical element to make the coin

4. Objectives Use AA and ICP to determine the amount of Copper in pennies from post and pre-1982 Compare our results to the expected values of 95 % Copper for pre-1982 and 2.5 % for post-1982 Also compare that to the amount of Copper in dimes within the same time periods, to see if the Copper changes occurred in them too

5. Method Weighed out 20 coins (10 of each type) to determine theoretical concentration of Cu Dissolved 16 coins (8 of each type) in HNO 3 (12 mL, 15 M, 48 h) Made standards to correspond to theoretical concentration of Cu Diluted samples with distilled water Ran samples through AA and ICP Analyzed data provided

6. Coin Data

7. AA Standards

8. AA Samples

9. Percent Error

10. ICP Standards Concentration=0.0021(int)-0.3502Concentration=0.00005(int)-0.5964

11. ICP Samples Concentration=0.0021(int)-0.1795Concentration=0.00005(int)-0.0522

12. Percent Error

13. Results The overall trend followed with our idea that as mass increased, the Copper content would increase Also supported the theory that the composition changed over the years, specifically from pre- to post-1982 It is obvious that the samples were much higher than the standards prepared, at least with the AA The ICP, being the ever-temperamental piece of equipment that it is, gave the exact opposite results that the AA produced

14. Conclusions It is inconclusive based on the data we obtained as per the percentage of Cu in dimes and pennies Due to the many reasons on the next slide…

15. Problems Our standards did not match up to where we believed that our samples would be The ICP seems to have changed its mind on the reading it gave for a blank sample of distilled water between the dates of 24/4 and 29/4 We believe that we added to the burning of the torch head of the ICP, and we are sorry for that, but if it is any consolation, we didn’t get any reliable results, so it got us back, immediately

16. Sources http://www.usmint.gov/about_the_mint/fun_facts/index.cfm ?flash=no&action=fun_facts2 http://www.usmint.gov/about_the_mint/fun_facts/index.cfm ?flash=no&action=fun_facts2 http://www.scholieren.com/proef/35020

17. Questions?