CONTROL OF MOS BY CHEMICAL AGENTS CONTD..

C) HALOGENS:
               Halogens is any of the five elements( Iodine, Bromine,Chlorine, Fluorine, Astatine ) in Group VII A of periodic table. They are highly reactive elements which contains seven electron in their outer shell in normal state. Iodine & chlorine are more commonly used as disinfectants.


  1. Chlorine: Chlorine is applied as chlorine gas, sodium hypochlorite & calcium hypochlorite . Since chlorine gas is difficult to handle, different compounds are used which are effective & easy to handle like; 



  • Hypochlorite: Hypochlorite release free chlorine in solution. Eg:  Sodium hypochlorite calcium hypochlorite. Sodium hypochlorite's 5% solution is called bleach. Calcium hypochlorite is known as chlorinated lime. To know about halogens as disinfectants please visit this link http://en.wikipedia.org/wiki/Halogen.
  • Chloramines : The organic compounds that contains chlorine like chloroamine-T. They are used as disinfectant, antiseptics,or sanitizing agents. Chloramines are very stable compound  that release chlorine over long periods. They are relatively effective in organic matter, but they have the disadvantages of acting more slowly & being less effective purifiers than any other chlorine compounds.  
                      
                       
Chloramines are used to sanitize glassware & eating utensils & to treat diary & food manufacturing equipment. Ammonia is usually mixed with chlorine n water treatment systems to form chloroamine. Chloramines control taste & odor problems caused  by the reactions of chlorine with nitrogenous compounds in water. Because chloramines  are less effective as germicides, sufficient chlorine must be added to ensure a residual of chlorine in the form of hypochlorite.

Uses:
  • Chlorine compounds are used in water treatment , food industries, domestic use & medicines.
  • Calcium hypochlorite is used in sanitizing daily equipment & utensils.
  • 1% sodium hypochlorite is used as household disinfectants, personal hygiene, Sanitization in diary & food industries.  
  • Chloramines are used for wound cleaning & root canal therapy. 


MODE OF ACTION: 
                                    Chlorine gas, sodium hypochlorite, calcium hypochlorite all release hypochlorous (HOCL) when added in water.  The hypochlorous  acid further decomposes into nascent oxygen which is a strong oxidizing agent. This nascent oxygen causes oxidation of cellular materials & destroys mos. Chlorine is also supported to combine directly with proteins of cell membrane, enzymes, & cell disruption.  For more please go to the links below:

http://water.me.vccs.edu/courses/ENV149/chlorinationb.htm
http://www.cmmonline.com/articles/the-science-of-disinfectants-7
http://www.lenntech.com/processes/disinfection/disinfection.htm?gclid=CKCr2fjakLYCFQQb6wodoS4AwQ




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