Astringent – Pharmaceutical Inorganic Chemistry B. Pharma 1st Semester



• Astringent

• The monograph analysis of:

 Zinc sulphate

 Potash alum


At the end of this
lecture, the student will be able to:

• Define astringent

• Explain the monograph analysis of:

 Zinc sulphate

 Potash alum


• The word “astringent” derives from Latin
adstringere, meaning “to bind fast”

• Definition: Astringent is a drug that reacts chemically
with cellular proteins producing limited coagulation which is accompanied with
shrinkage of body tissues

• Astringent protects from external irritation and reduces
cellular permeability

• It also possesses local styptic and local antiseptic

 Astringent medicines cause shrinkage of mucous membranes
or exposed tissues and are often used internally to check discharge of blood
serum or mucous secretions

 This can happen with a sore throat, hemorrhages, diarrhea,
or with peptic ulcers.  Externally applied
astringents, which cause mild coagulation of skin proteins, dry, harden, and
protect the skin

 Acne sufferers are often advised to use astringents if
they have oily skin

Uses of

• Cleaning the face and preventing Acne Breakouts

• Stopping bleeding

• Relieving the discomfort and itching of insect bites,
minor abrasions and Athlete’s foot

• Haemorrhoids

of zinc sulphate

Name: zinc

Chemical formula:
ZnSO4, 7H2O

Molecular weight:

Standards: Zinc Sulphate
contains not less than 99.0 per cent and not more than 104.0 per cent of ZnSO4,

Method of

Zn + H2SO4 + 7H2O à ZnSO4 7H2O + H2

Properties of zinc


• A Colourless, transparent crystals or a white, crystalline

• Odourless

• Efflorescent

Solubility: Very
soluble in water and glycerine and insoluble in alcohol

Test for purity

• Appearance of solution

• Chlorides

• Arsenic

• Iron

• Acidity/Alkalinity

Assay Principle

Complex metric, Direct titration

ZnSO4 + 2CH3COOH à Zn (CH3COOH)2

Zn (CH3COOH)2 + di Na EDTA à Zn EDTA complex

xylenol orange triturate

Buffer: hexamine

Titrant: Di
sodium EDTA

Colour change:
violet pink- yellow

Storage: Store
protected from moisture, in non-metallic containers

Medicinal uses:

• Astringent

• Emetic

of Potash alum

Name: Potash alum

Chemical formula: KAL(SO4)2.12H2O

Molecular weight: 474.4

Standards: It contains not less than 99.5 per cent

Method of Preparation:

K2SO4 + Al2(SO4)3 + 24H2O à KAL(SO4)2.12 H2O

Properties of Potash


• A Colourless, transparent crystals or a white, crystalline

• Sweet astringent taste

• Heated to 200oC, loses its water of crystallisation
and becomes anhydrous

Solubility: Very
soluble in water and insoluble in alcohol

Test for purity

• Heavy metals

• Zinc

• Arsenic

• Iron

• Ammonium salt

Storage: Store in
a well closed containers

Medicinal uses:

• Astringent and antiseptic

• Due to its protein precipitation used in the preparation
of toxoids

• Astringents: protein precipitants

• Zinc sulphate: Is prepared by adding sulphuric acid on
metallic zinc, assayed by complexometric direct titration and medicinally used
as astringents and emetic

• Potash alum: used as astringent, double salt, used for
water purification

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