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Indicators

• Titration indicators are added to the solution to change color when the solution switches passes a certain pH. Examples of such indicators are litmus, methyl orange and phenolphthalein. Since they react with the solution being measured, indicator use should be moderate---only a few drops if possible.
  
  

Equivalence Point

• The point at which the titrant uses up all the titer is called the "equivalence point." Another few drops of titrant would change the pH from neutrality significantly; therefore, indicators need not change color exactly at the equivalence point's pH.
  
  

Titration Curve

• The titration curve is usually a graph of the volume or mass of added titrant versus the titer's pH, read from a pH meter. Such a curve could also graph the titrant against the conductivity of the solution. In either case, the curve is very steep at the equilibrium point, which makes determination of the precise titrant volume added easy.
  
  

Potentiometric Titration

• Since acids and bases conduct electricity better than neutral water, conductivity is another useful indicator of the equivalence point. In potentiometric titration, electrodes are immersed into the titer and voltage or current points are recorded. The titration curve will again be steep at the equivalence point. The conductance has a minimum at the equivalence point. Potentiometric titration has the advantage of avoiding an indicator reacting with the solution being measured.
  
  

Titration for Water Concentration

• The solution on which titration is performed need not be aqueous. For example, Karl Fischer titration tests for water concentration in a solution. The original reactions by Fischer used methanol as the solvent.
  
  

Equilibrium and Full Reaction

• Chemical reactions don't generally fully react in one direction or the other. A balance between concentrations of reactants and products is achieved. For the purpose of titration, this isn't helpful, since the solvent in the titer needs to react fully. To achieve this, sometimes a catalyst is added to swing the equilibrium balance to one side.