43. the degree of flocculation of a suspension is 1.5 and the sedimentation volume is 0.75. what will be the ultimate volume of deflocculated suspension ?

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  1. 2.0
  2. 1.5
  3. 0.75
  4. 0.5


Saraswathi.B's picture




Pharmaceutical suspensions may be defined as coarse dispersion in which insoluble solids are suspended in a liquid medium. the liquid medium is usually water or a water based vehicle and the insoluble solids may have a size range from 10 to 1000 nm. Suspensions are also called as heterogeneous systems or biphasic systems.

Based on the proportion of solids suspensions are classified in to

dilute suspensions - it contains 2 to 10% w/v solids. eg: cortisone acetate, prednisolone acetate

concentrated suspensions - it contains solids as high as 50 % w/v. eg: zinc oxide, procaine pencilline G suspension.

based on the nature and behavior of solids suspensions are classified in to

deflocculated suspensions - in this system solids are present as individual particles. they also exhibit aggregation but comparatively at a slower rate than the flocculated particles. these systems have a shorter shelf life but have greater bio availability when comparatively to flocculated systems.

flocculated suspensions - in this system particles aggregates themselves by chemical bridging. these flocs are light, fluffy conglomerates which are held together by weak vander waals forces of attraction. aggregation is achieved by adding flocculating agents.

degree of flocculation

degree of flocculation = sedimentation volume of flocculated system / sedimentation volume of deflocculated system


degree of flocculation = ultimate sediment volume of flocculated system / ultimate sediment volume of deflocculated system

1.5 = 0.75 / ultimate sediment volume of deflocculated system

ultimate sediment volume of deflocculated system = 1.5 / 0.75 = 2.

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