Other titrations

Methyl yellow

Acid: Red

Base: Yellow

Methyl red

Acid: Red

Base: Yellow

Methyl orange

Acid: Pink

Base: Yellow

Phenolphthalein

Acid: Colorless

Base: Pink

Thymolphthalein

Acid: Colorless

Base: Blue

ACIDIMETRY: Aqueous

VS: HCl, H2SO4

Std: Na2CO3(OH) – Old ; Tromethamine – New

Indicator: Methyl red, Methyl orange

ACIDIMETRY: Non-aqueous

VS: HClO4 in GAA (Perchloric acid in glacial acetic acid/dioxane)

Std: KHP (Potassium dihydrogen phthalate)

Indicator: Crystal violet (Violet → Green)

ALKALIMETRY: Aqueous

VS: NaOH,Non-aqueous KOH

Std: KHP (Potassium dihydrogen phthalate)

Indicator: Crystal violet (Violet → Green)

Non-aqueous

✓ Sample is insoluble in water

✓ Sample is too weak to be titrated in water

PERMANGANOMETRY: VS

• KMnO4 (OA) – acidic medium

• Covered in foil; protected from light

• Brown ppt = MnO2

PERMANGANOMETRY: Std

• Na2C2O4 (New)

• As2O3 (Old)

PERMANGANOMETRY: Analyte

Reducing agent

PERMANGANOMETRY: Analyte

None (self-inducing)

PERMANGANOMETRY: Endpoint

Colorless to pale pink (15-30 sec)

PERMANGANOMETRY: Example

Direct: H2O2 Topical Solution

Indirect: Malic acid in cherry juice

Residual: NaNO2, KNO2

CERIMETRY: VS

Ce(SO4)2

CERIMETRY: Std

• Na2C2O4 (New)

• As2O3 (Old)

CERIMETRY: Analyte

Reducing agent

CERIMETRY: Endpoint

Red to blue

CERIMETRY: Example

• FeSO4 tablet

• Vitamin K (Menadione Na)

• Hydroquinone

IODIMETRY: Type

Direct with Iodine (brown)

IODIMETRY: VS

I2 (OA)

IODIMETRY: Std

Na2S2O3 VS (Sodium thiosulfate)

IODIMETRY: Analyte

Reducing agent

IODIMETRY: Indicator

Starch TS (added in the start)

IODIMETRY: Endpoint

Colorless to blue

IODIMETRY: Example

Vitamin C (Old), Calomel, NaHSO3

Analyte: I2 Solution (2%), Strong I2 (5%) Titrant: Na thiosulfate (Na2S2O3 VS)

IODOMETRY: Type

Indirect with liberated I2

IODOMETRY: VS

Na2S2O3 (RA)

IODOMETRY: Std

K2CrO7

IODOMETRY: Analyte

Oxidizing agent

IODOMETRY: Indicator

Starch TS (added before endpoint)

IODOMETRY: Endpoint

Blue to colorless

IODOMETRY: Example

CuSO4, NaOCl, Phenol, Resorcinol

Diazotization Titration

• Direct titration of primary aromatic amines using NaNO2 VS in acidic medium

• E.g. Sulfa drugs, dapsone, procaine, tetracaine

Dichlorophenol-Indophenol Titration

new test for Vit C

Iodimetry

old test for Vit C

Complexation Titration (Compleximetry)

• Current method of choice for the determination of polyvalent metal ions (eacceptor)

• Titrant: Disodium EDTA (Ethylenediamine tetraacetate) – e- donor; hexadentate ligand

Divalent

Ca2+, Mg2+, Mn, Zn (Direct)

Trivalent

Al, Bi (Residual)

Masking

special technique for determination of a metal in the presence of another metal

Complexation Titration: Methods

• pH adjustment

• Precipitation

• Use of masking agents

pH adjustment

o Acidic – trivalent

o Basic – divalent

Precipitation

e.g. Na2S TS or thioacetamide

Use of masking agents

compounds capable of entering a complexation reaction

o Triethanolamine: Fe, Al, Mn

o Thioglycols: Hg, Cu, Pb, Bi

o CN- : Cu, Co, Ni, Zn

o F - (NH4F): Mg, Al, Ca

Ca2+

Type: Direct

VS: Na2 EDTA

Std: CaCO3

pH:

Indicators:

Endpoint: