How to Test for Copper Content in Brass

Preparing the Standard Solutions

• 1

  Add 8 drops of 0.5 mol dm^-3 copper nitrate and 32 drops of distilled water to the first well of a well plate.

• 2

  Add 10 drops of copper nitrate and 30 drops of distilled water to the second well. For each succeeding well, add two drops of copper nitrate to the solution and subtract two drops of water.

• 3

  Fill the first two rows of the well plate with progressive copper solutions, ending with 30 drops of copper nitrate and 10 drops of water in the 12th well.

Preparing the Brass Solution

• 4

  File the brass sample until you obtain around 1/3 gram of brass filings. Carefully measure the filings and note the mass.

• 5

  Place the filings in a volumetric flask. Under a fume hood, add 10 drops of nitric acid to the brass filings, swirling the solution gently until the reaction ceases. Repeat until the brass dissolves completely. Note the number of drops of nitric acid required to dissolve the brass.

• 6

  Add distilled water to the solution until you have 10 cubic centimeters of the mixture. Cap the flask and invert it a few times to mix.

• 7

  Compare the color of the brass solution to the standard copper solutions in the well tray.

• 8

  Check the copper-nitrate-to-water ratio of the standard solution which most closely matches the brass solution. For example, if the brass solution matches the first well, the copper content of the brass solution is 0.5 x 8/32 mol dm^-3.