I have a piece of metal here and I'm not sure if it's copper or brass, but I need to find out. I figure the easiest way to find out is to oxidize some of it and see if it turns green, correct? Could anyone give me a method that will oxidize copper relatively quickly?
Visually: Copper is brownish-red, like a penny. Brass is a golden color. Oxidizing: Copper will oxidize more easily than brass. Copper oxides are green or blue, and brass oxides are black. Add a bit of acid--vinegar or lemon juice are acidic household chemicals. At first it may get shinier. Oxidation can be hastened by using hydrogen peroxide (found in a brown bottle at the drugstore) in addition to the acid.
RE: Quick way to oxidize copper with household chemicals? I have a piece of metal here and I'm not sure if it's copper or brass, but I need to find out. I figure the easiest way to find out is to oxidize some of it and see if it turns green, correct? Could anyone give me a method that will oxidize copper relatively quickly?
Bleach will oxidize it. Brass will oxidize, just not as much as copper, so unless you have a comparison sample, this won't be a great test.
Brass is mostly copper combined with zinc. Both copper metal and brass form a patina. The green patina of copper is actually a mixture of several compounds including CuCl2, CuSO4, CuCO3 and CuO. Copper(II) oxide is blue, but forms very small particles, and so copper(II) oxide often appears black. Brass may also form a green patina. The patina idea, while interesting is not the easiest, nor the best way to distinguish brass from pure copper. A better test is to compare the densities of the two metals. You can determine the volumes by liquid displacement and measure the masses with a balance. Compute the density with D=m/V. The density of copper is 8.94 grams per cubic centimeter, and the density of brass (depending on the composition of the mixture) is 8.4 to 8.7 grams per cubic centimeter.
