PURIFICATION PROCEDURES OF

COLLOIDS

Prepared By:Shashi Bhusan Rath

B.Pharm

Purification

It is the process of rendering something pure, i.e., clean of foreign elements.

The act of process of purifying or the removal of impurities.

Procedures

A particular method for performing a task. A series of small tasks or steps taken to

accomplish an end. Similar to METHOD, PROCESS & ROUTINE.

Colloids

A colloid is a substance in which microscopically dispersed insoluble particles are suspended throughout another substances.

Ex: Milk is an emulsified colloid of liquid butterfat globules dispersed within a water-based solution.

Example of Colloidal systems…

What is purification of collids?

The separation of constituents of the collidal solution with the help of any separation process such as centrifugation, dialysis,etc is known as Purification of Collids.

Why purification of collids?

When a collidal solution is prepared is often contains certain electrolytes which tend to destabile it that is why the purification of collids is done.

Procedure of Purification of Collids

The procedure or method for purification of collids are:-

DialysisElectro-dialysisUltrafiltrationCentrifugarion

Dialysis A method of separating molecules or

particles of different sizes by differential diffusion through semi-permeable memebrane is known as Dialysis.

The process of separating particles of collid from those of crystalloid by means of diffusion through a suitable membrane is called Dialysis.

Thomas Graham (chemist), the founder of dialysis and father of colloid chemistry.

Principle or Technique of Dialysis

Its principle based upon the fact that collidal particles can not pass through membrane while the ions of electrolyte can pass through it.

This process is based on the fact that membranes contain very small pores through which only dissolved molecules and ions of the true solution can pass readily.

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The impurities slowly diffused out the bag leaving behind pure collidal solution.

The fresh or distilled water is changed frequently to avoid accumulation of the crystalloids other wise they may start diffusing back into the bag.

Figure Representation….

Application of Dialysis…

Used in purifying blood through a membrane.

Can be used for removing HCL from the Ferric Hydroxide 80%.

Electro-dialysis

To increase the process of purification the dialysis is carried out by applying electric field. This process is called electrodialysis.

Electrodialysis is done in the presence of an electric potential across the membrane especially one using an ion selective membrane.

Principle of Electodialysis…

Used when the substances being removed is an electrolyte, substance is removed under an electronic field.

The electolyte ions pass through the membrane due to electrostatic pull of oppositely charges electrodes.

Figure Representation….

Application.... The important application of

electrodialysis process in the artificial kindney machine used for purification of blood of the patients whose kidneys have failed to work.

The artificial kidney machines work on the priciple of dialysis.

It is also used for deionization the aqueous solution.

Used for Glycerin purification.

Simple Mechanism…..

Ultra-filtration It is a filtration in which forces like pressure

leads to a separation through a semi-permeable membrane.

Filtration which only allows small molecules through semi-permeable membrane.

Here colloids are separated from crystalloids with the help of ultra filter paper.

The ultra filter paper was obtained by treating simple filter paper with gelatin.

In this ultra filter paper the pores are less or narrow in size through which only crystalloids particles can pass.

Figure Representation….

Centrifugation

Impurities are removed from colloids with the help of a machine of high speed called centrifugal machine. Colloids settle down while impurities remains in centrifuge.

Figure Representation….