Basic Concepts in Clinical Biochemistry-A Practical Guide.7z

6.2.1 Normality (N)

Normality can be defined as the number of equivalents of a solute dissolved in 1 litre
of solution. An equivalent is the molecular mass of the acid or base expressed in
grams divided by the number of moles of hydronium or hydroxyl ions produced by
this amount of acid or base.

N¼

Molecular mass 1000

Equivalent weightvolume mlðÞ

The equivalent weight of an acid can be calculated as

Equivalent weight¼molecular weight of an acid=basicity

The basicity of an acid is defined as the number of replaceable hydrogen atoms
present in one molecule of acid. That is, for hydrochloric acid (HCl), molecular
weight is 36.5, and basicity is 1, so equivalent weight is 36.5; however, in case of
sulfuric acid (H 2 SO 4 ), molecular weight is 98, and basicity is 2, so equivalent weight
will be 98/2¼49.
The equivalent weight of a base can be calculated as

Equivalent weight¼molecular weight of an base=acidity

The acidity of a base is defined as the number of hydroxyl ions which a molecule
of base can furnish in aqueous solution. For example, acidity for NaOH is 1, and for
Na 2 CO 3 ,itis2.
The normality of given conc./stock solution can be calculated as

N¼

%purityspecific gravity 1000

Equivalent weight 100

If we have to prepare a solution of specific normality from a given stock solution
of acid/alkali with known normality, then such solutions can be prepared by apply-
ing the relationship given below:

N 1 V 1 ¼N 2 V 2

where

N 1 ¼normality of stock solution
V 1 ¼volume of stock solution
N 2 ¼normality of solution to be prepared
V 2 ¼volume of solution to be prepared

6.2 Normal Solutions 23