Colloid Lab Report

Introduction in 1861 thomas graham observed that crystalline substances can easily pass through semipermeable membrane while particles of glue gelatin and gum can not pass , depending upon size of pariticles solution is divided into three types true solution: solution which is completely homogenous and have (0.1 – 1 nm) particle size suspension: solution of suspended particles in liquid which settle down at the bottom e.g sand in water and particle size is bigger than 1000 nm

Colloids: colloids consist of dispersed particles distributed throughout system also called colloidal solution or colloidal dispersion .in colloids particles neither completely dissolve like solution nor settle down like suspension but intermediate between true

. Depending upon dispersed phase and dispersion medium, there are eight types of colloidal solutions:

Classification of colloids

Depending upon type of interaction betwwen dispersed media and dispersed phase there are two classes of colloids

Hydrophilic colloids :

These are water loving colloids easily spread throughout medium and are easiy to prepare .these colloids are stable because there are strong forces of interaction between colloidal particles and liquid

These are also called Reversible colloids because on evaporating the liquid, the residue left will passes into colloidal state on addition of liquid.

Examples: agar is a reversible hydrocolloid of seaweed extract; it can exist in a gel or liquid state and can alternate between states with either heating or cooling. proteins -nucleic acids -micelles of soaps also form hydrophilic colloids

hydrophobic colloids:

These colloids, also known as emulsion are water repellent and lack the tendency to mix with water so are difficult to prepare. As there are weak forces of intearaction between water and particles so these are unstable

Coagulation

In hydrophobic colloids the dispersed particles can be separated from dispersion medium as precipitate this is called coagulation. Normally coagulation is done by adding electrolytes which result in neutralizing the colloids particles which then start accumulating as clusters

However Coagulation can be carried out by adding concentrated salt solution e.g NH4)2SO4, Na2SO4 in colloidal solution , by heating with mineral acids which cause denaturation and by using ultrafilters.

Applications of colloids

Colloids have various applications in medicine, industries,

1. Most of our medicines are colloidal in nature. Colloidal particles are finely divided and can easily absorbed by our body so colloids are used as therapeutic agents in different areas

2. Larger number of our foods are colloidal in nature. Milk is an emulsion of butterfat in water protected by a protein. Icecream , mayonnaise, cheese, cream and butter are also colloidal.

3. Water contain colloidal charged particles, we can purify water by adding electrolyte like alum which remove the collidal impurities and purify the