Page 40 - Pharmaceutical analytical chemistry |

5) Determination of water hardness
Hard water is the water that contains salts of calcium and magnesium
principally as bicarbonates, chlorides, and sulfates. Water hardness that is
caused by calcium bicarbonate is known as temporary hardness,
because boiling converts the bicarbonate to the insoluble carbonate. On
the other hand, hardness from the other salts is called permanent
hardness. Total hardness can be determined by many methods, e.g. the
palmitate method, while the permanent hardness is determined by the
soda reagent method.
In the palmitate method, the water sample is titrated with a standard
solution of potassium palmitate. The palmitate anion precipitates Ca2+
and Mg2+ ions. Any excess amount of the palmitate solution will be
hydrolyzed rendering the solution alkaline to phenolphthalein.

6) Direct titration of basic substances
A large number of bases, both organic and inorganic, are determined by
titration with standard acid. Sodium hydroxide is analyzed for total alkali
and for carbonate, the usual contaminant of the hydroxide.

7) Determination of amino acids
R – CH – COOH + CH2O ⎯→ R – CH – COOH

NH2 N = CH2

8) Determination of carbonyl compounds

C = O + NH2OH.HCl → C = NOH + H2O + HCl
The resulting acid is titrated with a standard base.

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