TYPES OF TITRATIONS

BASED ON INDICATION OF ENDPOINT

• Visual Titration

• Potentiometric Titration

• Electrometric Titration

Visual Titration

makes use of indicators to make observation of endpoint possible

Potentiometric Titration

equivalence point is signified by a sharp change in potential of the solution; pH meter

Electrometric Titration

equivalence point is signaled by a change in electrical conductivity

BASED ON NATURE

• Direct Titration

• Residual Titration

• Blank Titration

• Indirect Titration

Direct Titration

analyte is reacted with titrant after rendering it soluble in the titration medium

𝑷 = 𝑵 × 𝑽 × 𝑴𝑾 / 𝒇 × 𝟏𝟎𝟎𝟎 / 𝒘𝒕 𝒐𝒇 𝒔𝒂𝒎𝒑𝒍𝒆 (𝒊𝒏 𝒈𝒓𝒂𝒎𝒔) × 𝟏𝟎0

Residual Titration

two titrants are used wherein one VS is added in excess (T1) and then the unreacted excess is back titrated with the other VS (T2)

%𝑷 = (𝑵𝟏 𝑽𝟏 − 𝑵𝟐 𝑽𝟐) × 𝑴𝑾 / 𝒇 × 𝟏𝟎𝟎𝟎 / 𝒘𝒕 𝒐𝒇 𝒔𝒂𝒎𝒑𝒍𝒆 (𝒊𝒏 𝒈𝒓𝒂𝒎𝒔) × 𝟏𝟎0

Residual Titration: Indications

• Insoluble sample

• Volatile sample

• Reaction is too slow

• No sharp end point

Direct with Blank

%𝑷 = 𝑵 × (𝑽𝒂 −𝑽𝒃) × 𝑴𝑾 / 𝒇 × 𝟏𝟎𝟎𝟎 / 𝒘𝒕 𝒐𝒇 𝒔𝒂𝒎𝒑𝒍𝒆 (𝒊𝒏 𝒈𝒓𝒂𝒎𝒔) × 𝟏𝟎0

Residual with Blank

%𝑷 = 𝑵 𝒃𝒂𝒄𝒌𝒕𝒊𝒕𝒓𝒂𝒏𝒕(𝑽𝒃 − 𝑽𝒂) × 𝑴𝑾 / 𝒇 × 𝟏𝟎𝟎𝟎 / 𝒘𝒕 𝒐𝒇 𝒔𝒂𝒎𝒑𝒍𝒆 (𝒊𝒏 𝒈𝒓𝒂𝒎𝒔) × 𝟏𝟎0

Indirect Titration

analyte undergoes preliminary treatment prior to titration (e.g. Assay of Malic Acid in Cherry Juice)

Malic Acid + CaCO3 → CaC2O4 – titrated with KMnO4 VS

Acidimetry: Direct

NaHCO3, KHCO3

Acidimetry: Residual

ZnO, Milk of Magnesia

Alkalimetry: Direct

Dilute H3PO4

Alkalimetry: Residual

Aspirin

ACIDIMETRY

Titrant: Acid

Analyte: Base

ALKALIMETRY

Titrant: Base

Analyte: Acid

SA + SB

Phenolphthalein, Methyl red, Methyl orange

WA + SB

Phenolphthalein

WB + SA

Methyl red, methyl orange

WB + WA

Not possible