answersLogoWhite

0

Colored substances contain molecules with chromophores, areas of the molecule that have double bonds between carbon atoms or oxygen atoms. A good example is beta carotene, and that section goes into more detail on how molecules become colored.

Bleaches attack these chromophores in one of two ways.

Oxidizing bleaches like sodium hypochlorite break the molecules at the double bond. This results in either a shorter molecule that does not absorb visible light, or a molecule whose chromophore is either shorter or non-existant. A shorter chromophore will absorb light of a shorter wavelength than visible light (such as ultraviolet light), and so does not appear colored.

Reducing bleaches such as lemon juice (in combination with sunlight) or sulfur dioxide, convert the double bonds in the chromophore into single bonds, eliminating its ability to absorb visible light. Sometimes the reaction is reversible, where oxygen in the air reacts with the molecule to repair the chromophore, and the stain returns.

Another chlorine bleach often used is sodium dichloroisocyanurate.

Oxygen bleaches also work by releasing oxygen. Hydrogen peroxide is the active ingredient, either as itself, or as a product of reacting another ingredient with water to release hydrogen peroxide.

Oxygen bleaches such as sodium carbonate peroxide (also called sodium percarbonate), sodium peroxide, or sodium perborate are made by reacting molecules with hydrogen peroxide. When the result is added to water, the hydrogen peroxide is released.

Borax also works by releasing hydrogen peroxide into the water.

Most oxygen bleaches work best in hot water. Additives such as tetra acetyl ethylene diamine allow the hydrogen peroxide to work in warm water (50° C).

User Avatar

Wiki User

17y ago

What else can I help you with?

Related Questions