What Is Bleach ? ¯¯¯¯¯¯¯¯¯¯¯¯¯¯ A bleach is a chemical that can remove or lighten color, usually via oxidation. Types of Bleaching agents ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 1. Chemical bleaching agents:- ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ * Oxidizing bleaching agents * Reducing bleaching agents 2 Energy ¯¯¯¯¯¯¯¯¯¯ Chemical bleaching agents:- ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 1. Chlorine bleach usually contains sodium hypochlorite 2. Oxygen bleach contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate 3. Bleaching powder is calcium hypochlorite *** Other bleaching agents include sodium persulfate sodium perphosphate sodium persilicate and their ammonium, potassium and lithium analogs, calcium peroxide zinc peroxide sodium peroxide carbamide peroxide chlorine dioxide bromate organic peroxides ex: benzoyl peroxide *** Most bleaches are oxidizing agents But there are reducing agents that can be used as bleach. Ex:- sodium dithionite How Bleach Works ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ Oxidizing bleach ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ It works by breaking the chemical bonds of a chromophore (part of a molecule that has color). This changes the molecule so that it either has no color or else reflects color outside the visible spectrum. Reducing bleach ¯¯¯¯¯¯¯¯¯¯¯¯¯¯ It works by changing the double bonds of a chromophore into single bonds. This alters the optical properties of the molecule, making it colorless. 2. Energy:- ¯¯¯¯¯¯¯¯¯ Energy can disrupt chemical bonds to bleach out color. Ex:- The high energy photons in sunlight like UV can disrupt the bonds in chromophores to decolorize them.
Posted on: Wed, 17 Jul 2013 17:40:00 +0000
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