General Knowledge - General Science - Discussion

The normal brown coloration on brass which slowly forms is primarily due to the oxidation of the copper (which makes up about 70% or more of the Brass alloy) to copper oxide. The greenish patina that forms on brass (especially in inclement environments) can be a complex of copper carbonates and acetates (acetates come from naturally or artificially occurring contaminants or droppings in the atmosphere depending on the presence of Industry).

Vinegar (acetic acid) is capable of producing an intense green corrosion on brass (copper acetate) and copper alloys generally. Regions near industry may be exposed to Sulfur compounds such as Sulfur Dioxide, or Hydrogen Sulfide. Both of these are potent copper oxidizers, hence the use of 'Liver of Sulfur' by artisans to oxidize copper, bronze, and brass castings.

Additionally Hydrogen Sulfide as well as liquid polysulfide concentrates are a potent oxidizer for Silver alloys as well. For this reason, do not keep your brass and silverware in a cabinet that also contains matches!

Zinc which is present in brass reacts with hydrogen sulphide to form zinc sulphide which is black in colour.

I never believed it was hydrogen sulphide.

Composition of Dry Air.

Substance % by volume.

Nitrogen, N2 78.08.
Oxygen, O2 20.95.
Argon, Ar 0.93.
Carbon dioxide, CO2 0.033.
Neon, Ne 0.0018.
Helium, He 0.00052.
Methane, CH4 0.0002.
Krypton, Kr 0.00011.
Nitrogen (I) oxide, N2O 0.00005.
Hydrogen, H2 0.00005.
Xenon, Xe 0.0000087.
Ozone, O3 0.000001.

In air H2S won't exists directly in air. Then how it will react?

Composition of Dry Air.

Substance % by volume.

Nitrogen, N2 78.08.
Oxygen, O2 20.95.
Argon, Ar 0.93.
Carbon dioxide, CO2 0.033.
Neon, Ne 0.0018.
Helium, He 0.00052.
Methane, CH4 0.0002.
Krypton, Kr 0.00011.
Nitrogen (I) oxide, N2O 0.00005.
Hydrogen, H2 0.00005.
Xenon, Xe 0.0000087.
Ozone, O3 0.000001.

In air H2S won't exists directly in air. Then how it will react?

I think it should have been oxygen. But @Poorna Chandra is right, how will it react ?

I can't understand.

Due to atmospheric pressure.

H2s is superconductor also.

Because it is homogeneous.