Colloid Molecules: Hydrated Colloid Particles

Colloids And Suspensions

ADITYA MAAN (14045007), GAURAV BARAK (14045032), MANOJ DHAKER (14045052)

INTRODUCTION A colloid is a substance which is microscopically dispersed throughout another substance. The word colloid comes from Greek word kolla, meaning glue thus colloidal particles are glue like substances. Colloidal particles pass through filter paper but not through a semipermeable membrane. Colloids can be made settle by centrifugation. Molecules of a hydrophilic colloid have an affinity for water molecules and thus when they are dispersed in water they become hydrated. Hydrated colloids swell and increase the viscosity of the system, thereby improving stability by reducing the interaction between particles and their tendency to

The solid particles along the dispersion medium are fed into the colloidal mill. The mill consists of two steel plates nearly touching each other and rotating in opposite directions with high speed (7000 rev/min).

(B) By peptisation: The process of converting a freshly prepared precipitate into colloidal form by the addition of suitable electrolyte is called peptization. The electrolyte is used for this purpose is called peptizing agent or stabilizing agent. Cause of peptisation is the adsorption of the ions of the electrolyte by the particles of the precipitate. Important peptizing agents are sugar, gum, gelatin and electrolytes.

Freshly prepared ferric hydroxide can be converted into colloidal state by shaking it with water containing Fe3+ or OH– ions, viz. FeCl3 or NH4OH respectively.

Fe(OH)3 + FeCl → [Fe(OH)3Fe]3+ + 3Cl–

Precipitate electrolyte Colloidal sol Chemical methods:

Some chemical reactions used to aggregate smaller particles of atomic or ionic size to form large particles of colloidal dimensions. Colloids can be prepared by following chemicals methods.

a)

These can then be used more easily, or absorbed more easily. Colloidal gold, for example, can be used in medicine to carry drugs and antibiotics, because it is highly non-reactive and non-toxic, unlike silver. Pharmaceutical industry makes use of colloidal solution preparation in many medicines. A wide variety of medicines are emulsions. An example is Cod Liver Oil. Paint industry also uses colloids in the preparation of paints. Asphalt emulsified in water is used for building roads. Colloids are frequently hard to extract or purify, which can lead to large losses in analysis or extraction having a large impact on the economics of the process.

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