Astringent
Contents
• Astringent
• The monograph analysis of:
Zinc sulphate
Potash alum
Learning
Objectives
At the end of this
lecture, the student will be able to:
• Define astringent
• Explain the monograph analysis of:
Zinc sulphate
Potash alum
Astringent
• 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
actions
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
astringents:
• Cleaning the face and preventing Acne Breakouts
• Stopping bleeding
• Relieving the discomfort and itching of insect bites,
minor abrasions and Athlete’s foot
• Haemorrhoids
Monograph
of zinc sulphate
Name: zinc
sulphate
Chemical formula:
ZnSO4, 7H2O
Molecular weight:
287.5
Standards: Zinc Sulphate
contains not less than 99.0 per cent and not more than 104.0 per cent of ZnSO4,
7H2O
Method of
Preparation:
Zn + H2SO4 + 7H2O à ZnSO4 7H2O + H2
Properties of zinc
sulphate:
Description:
• A Colourless, transparent crystals or a white, crystalline
powder
• 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
Indicator:
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
Monograph
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
alum:
Description:
• A Colourless, transparent crystals or a white, crystalline
powder
• 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