It is because the presence of mixture of hydrogen and sulphide and brass is a type of thing which has a color very light and mixture is non temperature (hot and cold type of temperature) so it gets discolored.

Explanation:

Brass is an alloy of copper and zinc. It gets discoloured in air due to the presence of certain gases. Hydrogen sulphide is one of the gases that cause the discoloration of brass. The following points explain why hydrogen sulphide is responsible for the discoloration of brass:

Presence of hydrogen sulphide:

Hydrogen sulphide is a gas that is produced naturally in the environment. It is commonly found in volcanic gases, natural gas, and some mineral springs. It is also produced by the decomposition of organic matter, such as sewage and manure. Hydrogen sulphide is a colourless gas with a strong, unpleasant odour similar to that of rotten eggs.

Reaction with brass:

When brass comes in contact with hydrogen sulphide gas, a reaction takes place that leads to the discoloration of the brass. This reaction is known as tarnishing. Hydrogen sulphide reacts with the copper in the brass to form copper sulphide. Copper sulphide is a black compound that forms on the surface of the brass, giving it a discoloured appearance.

Other gases:

Other gases in the environment, such as oxygen and carbon dioxide, can also react with brass and cause discoloration. However, these gases do not have as strong an effect on brass as hydrogen sulphide does.

Prevention:

To prevent the discoloration of brass, it is important to limit its exposure to hydrogen sulphide gas. This can be done by storing brass objects in a dry, well-ventilated area. It is also important to clean and polish brass objects regularly to prevent the buildup of tarnish.

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