Page 34 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

- Solution in nitric acid undergoes photo-chemical decomposition
but only slowly.

- Note: Ceric salt hydrolyzes to form ceric hydroxide if the solution
is not acidic.

Reduction half-reactions

Ce4+ + e Ce3+ E0 1.44 V (I M H2SO4)
Yellow-Orange

Eq wt = Mw / 1
Ep detection

Ferroin ind (red "Ferroin" to blue "Ferriin")

Solutions of Ce4+ are yellow-orange, but is not intense enough to
act as self- ind.

Applications

Direct Titrations

Determination of reducing species

[1] Determination of Fe2+ salts e.g. FeSO4

Fe2+ + Ce4+ Fe3+ + Ce3+
HCl/ Ferroin ind

[2] Determination of H2O2

2Ce4+ + H2O2 2Ce3++ O2 (g) + 2H+

[3] Determination of H2C2O4

50 oC

2Ce4+ + H2C2O4 2Ce3+ + 2CO2 + 2H+

[4] Determination of HNO2 2Ce3+ + NO3− + 2H+
2Ce4+ + NO2− + H2O

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