Analysis of Silver in an Alloy

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Analysis of Silver in an Alloy

Mark Andrew Garner

Gareth Smith

January 28 - February 1, 2008

Aim and Outcome:

The purpose of this lab was to calculate the percent of silver in an alloy using gravimetric analysis. Through the procedure mentioned in this report, the percent of silver in an alloy of a U.S. Mint dime made before 1965 was 90.2% ± 0.05%.

Introduction:

The alloy used for this experiment was a U.S. Mint ten-cent dime alloyed as silver and copper if made before the year 1965, after which mints began using copper and nickel instead. First, the dime piece was dissolved in nitric acid and the silver was precipitated as silver chloride. The precipitate was then filtered, washed, dried and weighed. To obtain the percent of silver in the alloy, the mass of silver chloride was compared to the mass of the original sample. Because the results are based on the mass of a product, the procedure is determined as gravimetric analysis.

Nitric acid (HNO3) is required as an "oxidizing agent" because silver and copper are very non-reactive metals and cannot dissolve in hydrochloric acid or sulfuric acid. The nitrate