31-10-2012, 04:59 PM
COLLOIDAL
[attachment=37638]
Introduction
A colloid or colloidal dispersion is a type of homogenous mixture. A colloid consists of two separate phases :
Dispersed phase & Continuous phase. The Dispersed phaseis made of tiny particles or droplets that are distributed evenly throughout the continuous phase. Homogeneous mixtures with a Dispersed phase in the size range 1 nm to 100 nm may be called colloidal aerosols, colloidal emulsions, colloidal foams, colloidal dispersions or hydrosols.
Classification of Colloids
Colloids can be classified on the basis of interactionbetween Dispersed phase (DP) & Dispersion medium (DM)
a) Lyophillic colloids / Hydrophilic colloids :
(i) Strong affinity is present between particles of DP & DM.
(ii) It’s reversible because DP & DM can be separated.
(iii) It’s stable & don’t get easily precipitated.
(iv) When DM is water , it’s called Hydrophilic.
Multimolecular colloids -
Colloidal particle is aggregate of small atom or molecule in which particles are held by vander Waal’sforce.
Macromolecular colloids –
Colloidal particles is big molecule or atom like colloidal solution of polymers. This type of colloidalsystem is very stable. No need of aggregation or subtraction.
Hydrocolloids
A Hydrocolloid is defined as a colloidal system where in the colloid particles are dispersed in water. Hydrocolloids can be either irreversible or reversible. For example, agar, can exist in a gel & sol state , & alternate between states with the addition or elimination of heat. Many Hydrocolloids are derived from natural sources like pectin is extracted from citrus peel & apple pomade. Hydrocolloids are employed in food mainly to influence texture or viscosity (e.g. – sauce). Hydrocolloids are also used in skin-care & wound –dressing.
[attachment=37638]
Introduction
A colloid or colloidal dispersion is a type of homogenous mixture. A colloid consists of two separate phases :
Dispersed phase & Continuous phase. The Dispersed phaseis made of tiny particles or droplets that are distributed evenly throughout the continuous phase. Homogeneous mixtures with a Dispersed phase in the size range 1 nm to 100 nm may be called colloidal aerosols, colloidal emulsions, colloidal foams, colloidal dispersions or hydrosols.
Classification of Colloids
Colloids can be classified on the basis of interactionbetween Dispersed phase (DP) & Dispersion medium (DM)
a) Lyophillic colloids / Hydrophilic colloids :
(i) Strong affinity is present between particles of DP & DM.
(ii) It’s reversible because DP & DM can be separated.
(iii) It’s stable & don’t get easily precipitated.
(iv) When DM is water , it’s called Hydrophilic.
Multimolecular colloids -
Colloidal particle is aggregate of small atom or molecule in which particles are held by vander Waal’sforce.
Macromolecular colloids –
Colloidal particles is big molecule or atom like colloidal solution of polymers. This type of colloidalsystem is very stable. No need of aggregation or subtraction.
Hydrocolloids
A Hydrocolloid is defined as a colloidal system where in the colloid particles are dispersed in water. Hydrocolloids can be either irreversible or reversible. For example, agar, can exist in a gel & sol state , & alternate between states with the addition or elimination of heat. Many Hydrocolloids are derived from natural sources like pectin is extracted from citrus peel & apple pomade. Hydrocolloids are employed in food mainly to influence texture or viscosity (e.g. – sauce). Hydrocolloids are also used in skin-care & wound –dressing.