Page 32 - Pharmaceutical Analytical Chemistry II - Pharm D Clinical- 07-PA202

Applications in Strongly alkaline solutions (2 M NaOH)
By Back Titration Technique

Determination of glycerol

C3H8O3 + 14MnO4− + 20 OH− 3CO32− +14MnO42− + 14H2O
3C = +8 -6 = -2 3C = +4 x 3 = +12

-2 to +12----------------- loss of 14 e

Eq wt glycerol = Mw / 14

Ba2+ is added to ppt manganate, to mask its green color

Acidify with H2SO4 and back titrate xss st MnO4− ≠ st H2C2O4

2MnO4− + 5H2C2O4 + 6H+ 70 o C

2Mn2+ + 10CO2 + 8H2O

II- Cerium (IV), Ce4+
Properties
- Strong oxidizing agent, E0 = +1.44 V

- Cerric solutions in sulfuric acid does not oxidize Cl− and can be
used to titrate HCl solutions of analytes

- Salts: Cerium (IV) ammonium nitrate, Ce(NO3)4.2NH4NO3
Primary standard

Its solution does not have to be standardized (if it is a pure grade)

Standard solutions and Stability

- Salt is dissolved in sulfuric acid, at least 0.1 M, to prevent pptn of
basic salts.

- Solution in sulfuric acid is indefinitely stable.

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