MgCl2 is added to polio-vaccine because of the following

(Vaccine can be kept in higher temperature) (491- A7th)* Molar MgCl2 protects the virus against heat inactivation* Poliovirus is resistant to ether, chloroform, bile protelytic enzymes of the intestinal contents and detergents* It is stable at PH-3* It is readily inactivated by heat (55degC for 30 minutes)* Chlorination destroys the virus in water, but organic matter delays inactivation* Phenolic disinfectants are not effective* Poliovirus does not survive lyophisation well