|
German version
Experimental procedure: 100 mL of a chlorine cleaner are poured into a gas collecting cylinder. A white coffee filter paper is soaked in beetroot juice. A small amount of vinegar essence is added to the houshold cleaner (caution: foams!). Then the top of the cylinder is covered with the wet, red colored coffee filter paper. Results: The part of the red colored filter paper, which covers the opening of the glass cylinder, turns colorless.  
Video clip (Download RealPlayer .rm file)Discussion and background: Wash-basins, toilets and the floors of bathrooms are cleaned using a strongly alkaline cleaner on sodium hypochlorite basis (NaOCl). The disenfecting of these cleaners is due to the conversion of hypochlorite to hypochlorous acid, which decomposes to form nascent oxygen (1).  NaOCl in cleaners is dangerous when these cleaners are mixed with cleaners on acid basis. Vinegar liberates chlorine from the hypochlorite containing cleaner (2).  Chlorine combines with water to form hydrochloric acid and hypochlorous acid ( Cl2 + H2O —> HCl + HOCl ). The red color of the beetroot juice comes from the pigment betanin. Active oxygen liberated in decomposition of hypochlorous acid ( HOCl —> HCl + O ) is responsible for the bleaching of the dye. The oxidizing bleach works by disrupting the conjugated pi-electron system of the chromophore responsible for light absorption Exposure to chlorine gas may cause severe irritation of mucous membranes of the nose, throat, and respiratory tract. If mixed with ammonia or ammonia-containing household chemicals (drain cleaners, automatic dishwashing detergents, oven cleaners), cleaners on chlorine basis release toxic chloramine gas, which may produce tearing, respiratory tract irritation, and nausea. Always wear rubber gloves when handling cleaners and use them in well-ventilated areas. |
 |
Reference:
G. Schwedt: Experimente mit Supermarktprodukten, Wiley-VCH-Verlag, Weinheim (Germany) 2001
Index of Lecture Experiments
