Page 49 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

Standard Solutions
Standard solutions are solutions of known concentration and composition.

Standard solutions are classified into 2 types:

(1) Primary Standard Solution.

It is a solution of exactly known concentration and
composition and its concentration remains constant for a long
period.

Definition
It can be directly prepared by weighing an exact weight of the

primary standard substance in a measuring (volumetric) flask,
dissolving it in a proper solvent and completing to a specified
volume.

1. It must be easily obtained in a very high grade of purity and
of known composition.
2. Very stable.
Requirement of 3. Non-hygroscopic and non-volatile.

a Primary 4. It can be dried at 105-110°C without decomposition.
Standard 5. It should have a high molecular weight to minimize weighing

Substance error. This facilitates accurate calculation of the molar

concentrations of solutions.
6. It must react with other substances in a quantitative way

according to balanced chemical equations.

• Acids:
potassium acid phthalate, oxalic acid, benzoic acid.

Examples

• Bases:
Borax, Na 2B 4O 7 & Sodium carbonate Na 2CO 3

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