If you Google "bleach" you will find there are many different types, i used Milton which is used to steralise babies bottles so they can't all be the same
http://chemistry.about.com/od/chemistryfaqs/f/bleach.htm
There are several types of bleach. Chlorine bleach usually contains sodium hypochlorite. Oxygen bleach contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate. Bleaching powder is calcium hypochlorite. Other bleaching agents include sodium persulfate, sodium perphosphate, sodium persilicate, their ammonium, potassium and lithium analogs, calcium peroxide, zinc peroxide, sodium peroxide, carbamide peroxide, chlorine dioxide, bromate, and organic peroxides (e.g., benzoyl peroxide).
While most bleaches are oxidizing agents, other processes can be used to remove color. For example, sodium dithionite is a powerful reducing agent that can be used as a bleach.