Page 74 - PC 101 practical notes 24-25..

MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL I PHARM. ANAL. CHEM. I (PC 101)

V Vo ol lh ha ar rd d' 's s M Me et th ho od d .
.

It is a type of precipitation titration that depends on the formation of

colored complex ions (colored solution) at the end point.

Main features of Volhard's method:

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• Sample: Cl , Br , I & SCN .
• Type of titration: Back (Residual) titration.

 1 standard (25 ml): AgNO 3.
st
• Standard Solutions:
 2 standard (titrant): NH 4SCN or KSCN.
nd

• pH: Acidic medium (HNO 3).

• Indicator: Ferric salts such as:

1) Ferric alum = Ferric ammonium Sulfate

{ FeNH 4(SO 4) 2.12H 2O }.

OR 2) Ferric nitrate { Fe(NO 3) 3 }.

• Color at E.P.: Faint orange or faint red color.

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