A pharmaceutical suspension is a liquid preparation in which fine solid particles of a medicine are dispersed in a liquid in which they do not dissolve. Over time, these particles settle down. Depending on how the particles behave, suspensions are of two types — flocculated and deflocculated. In a flocculated suspension the particles join into loose clusters called flocs, while in a deflocculated suspension the particles remain separate. Understanding the difference between them is important in pharmaceutics because it affects the stability and quality of the suspension.
A suspension has solid particles dispersed in a liquid in which they do not dissolve.
Flocculated suspension: particles form loose clusters called flocs.
Deflocculated suspension: particles remain separate.
Flocculated suspensions settle fast but redisperse easily and do not cake.
Deflocculated suspensions settle slowly but form a hard cake (caking).
In flocculated suspensions the supernatant becomes clear quickly.
Controlled flocculation is used to get the advantages of both types.
In a flocculated suspension, the suspended particles are loosely joined together to form light, fluffy clusters called 'flocs'.
Features: • Particles form loose aggregates (flocs). • The flocs settle rapidly because they are larger. • The sediment formed is loose and fluffy. • The sediment can be redispersed easily by shaking. • No hard cake is formed. • The supernatant liquid (the clear liquid above) becomes clear quickly.
Main drawback: because the particles settle fast, the suspension may look unattractive (it appears to separate quickly), but it is easy to shake back into a uniform mixture.
In a deflocculated suspension, the particles stay separate and do not join into flocs.
Features: • Particles remain as separate individual particles. • They settle slowly because they are small. • The sediment formed is closely packed and hard. • The sediment forms a hard 'cake' that is very difficult to redisperse — this is called caking. • The supernatant liquid remains cloudy for a long time.
Main drawback: although it settles slowly and looks good at first, once the particles settle they form a hard cake at the bottom that cannot be shaken back into suspension, which spoils the product.
Flocculated Suspension: • Particles form loose flocs • Rate of settling is fast • Sediment is loose and fluffy • Easily redispersed on shaking • No caking (no hard cake) • Supernatant becomes clear quickly
Deflocculated Suspension: • Particles remain separate • Rate of settling is slow • Sediment is hard and closely packed • Difficult to redisperse (forms a cake) • Caking occurs • Supernatant stays cloudy for long
In practice, a good suspension is often made 'controlled flocculated' to get the benefits of both — slow, even settling without hard caking.
In a flocculated suspension the particles join into loose clusters (flocs) that settle quickly but redisperse easily and do not form a hard cake. In a deflocculated suspension the particles remain separate, settle slowly, but form a hard, closely packed cake that is difficult to redisperse (caking). So flocculated suspensions settle fast but shake back easily, while deflocculated ones settle slowly but tend to cake.
A flocculated suspension is one in which the suspended particles are loosely joined together to form light, fluffy clusters called flocs. These flocs settle rapidly, form a loose sediment, do not cake, and can be easily redispersed by shaking. The supernatant liquid becomes clear quickly.
Caking is the formation of a hard, closely packed sediment at the bottom of a deflocculated suspension. Because the separate particles settle slowly and pack tightly, they form a hard 'cake' that cannot be shaken back into the liquid. Caking is undesirable because it spoils the suspension.
A flocculated suspension is generally preferred in pharmacy because it does not form a hard cake and can be easily redispersed, even though it settles quickly. To get the advantages of both, a 'controlled flocculated' suspension is often prepared, which settles slowly and evenly without forming a hard cake.
Periodic Table of First 20 Elements — Names, Symbols & Properties
Periodic table of first 20 elements from Hydrogen (H) to Calcium (Ca) with atomic number, symbol, atomic mass, electron configuration, valency, and properties.
Permanent Hardness of Water
Learn why permanent hardness of water cannot be removed by boiling. Understand the causes of permanent hardness and the methods used to remove it.
Phenolphthalein Colour in Acid and Base
Learn the colour of phenolphthalein in acidic, basic, and neutral solutions. A crucial acid-base indicator for Class 10 and 12 Chemistry titrations.
What Is the Chemical Formula of Phitkari (Alum)?
Phitkari (alum) formula is KAl(SO4)2·12H2O. Molecular mass 474 g/mol. Used in water purification, shaving, and dyeing. Learn its structure and uses.
What Is the Chemical Formula of Plaster of Paris?
Plaster of Paris formula is CaSO4·½H2O (calcium sulphate hemihydrate). Made by heating gypsum at 120°C. Sets hard by reabsorbing water. Learn its chemistry.
Turn this guide into revision flashcards, a practice exam, or an AI-generated podcast — free, no signup required.