Page 50 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

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

(2) Secondary Standard Solution.

➢ It is a solution of an approximately known concentration.

➢ Its concentration can not be directly calculated from the weight
of solute and volume of solution.

Definition
[Remember: Solute + Solvent = Solution]
➢ Its exact concentration is determined by a process called

“Standardization”.

➢ It is a process used to determine the exact concentration of

secondary standard solutions and correct any error if present.

➢ That is done by:
Standardization
ry
ry
Titrating the 2 standard solution against a 1 standard solution
ry
OR against a previously standardized 2 standard.
➢ Examples: HCl and NaOH

Steps for the determination of a sample using titration

➢ Preparation of the standard solution (usually HCl, H SO or NaOH) and
2 4
standardization of it by titration against a 1ry standard or a previously

standardized 2ry standard & then calculation of the correction factor (f).

f = Volume of the solution of EXACT normality  1ry or prev. standardized 2ry.

Volume of the solution of APPROXIMAT E normality  The prepared standard soln.
st
1 Step
a) If f = (0.95-1.05):  No modification in the preparation (i.e. the prepared
standard soln. is ready for use).

b) If f (< 0.95) or (> 1.05):  certain modification should be done in the
preparation by dilution or concentration & then (f) is recalculated to
ensure that it becomes 0.95-1.05.

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