From: poutnik4REMOVEnntp@CAPITALSgmail.com   
      
   Oumati Asami  Wrote in message:   
   > Just wonder why people use buffer solutions, instead of distilled water, to   
   calibrate PH meters. Can distilled water be used to calibrate PH meters for PH   
   7?   
      
   It cannot.   
   It's pH value is theoretically 7 at 25 deg C,   
   but practically it is extremely  sensitive on composition  of   
    traces of dissolved compounds from  vessel walls, in listing   
    dissolved gases.   
      
   E.g pH of precipitated water in rain is theoretically about 5.6   
    due dissolved CO2, practically even less due acidic sulphure and   
    nitrogen oxides and traces of sulphuric and nitric   
    acid.   
      
   Additionally, as it has extremely low buffer capacity,   
   electrodes of pH meter would in large extend determine,   
   what pH will be measured.   
   Something analogical like if you put a 100g massive thermometer to   
    10ml of water to measure it's temperature.   
   --   
   Libor Striz aka Poutnik ( a pilgrim/wanderer/wayfarer)   
      
   "Humour is the only effective weapon against stupidity."   
   Miloš Forman   
      
      
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