Colloids around us - class-XII

There are various applications of colloids-

• A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.
  
• Colloidal medicines are more effective because they have large surface area and are therefore easily assimilated.
  

• Purification of drinking water
  
• Cleansing action of soaps and detergents as Medicines
  
• Photographic plates and films
  

Tanning is the process that converts the protein of the raw hide or skin into a stable material which will not putrefy and is suitable for a wide variety of end applications. The principal difference between raw hides and tanned hides is that raw hides dry out to form a hard inflexible material that can putrefy when re-wetted (wetted back), while tanned material dries out to a flexible form that does not become putrid when wetted back. A large number of different tanning methods and materials can be used. The choice is ultimately dependent on the end application of the leather. The most commonly used tanning material is chromium, which leaves the leather, once tanned, a pale blue colour (due to the chromium), this product is commonly called wet blue.

Gelatin is a translucent, colourless, brittle (when dry), flavourless foodstuff derived from collagen obtained from various animal by-products. It is commonly used as a gelling agent in food, pharmaceuticals. Substances containing gelatin or functioning in a similar way are called gelatinous. Gelatin is an irreversibly hydrolyzed form of collagen. It is often used as an ingredient in the manufacture of ice-cream to stabilize the colloid and prevent crystal growth and works as protective colloid.

Lyophilic or solvent loving : When dispersed phase has a greater affinity for the dispersion medium, the colloids are termed as lyophilic and when the dispersion medium is water, they are given the name hydrophilic. They are also called natural colloids, substances like proteins, starch, egg albumin and rubber etc. are grouped under this category.The lyophilic colloids are also called Intrinsic Colloids.

As we know,
Smaller the gold number, higher the protective power of a colloid. Gold numbers of some protective colloids are given below :
Protective Colloid                       Gold Number    
Heamoglobin                                0.03 to 0.07        
Starch                                              15 to 25      
Gum Arabic                                      15 to 25        
Gelatin                                            0.005 to 0.1
so gelatin have maximum protective powers.

Smoke precipitator works on the principle of neutralization of charge on colloids.
Smoke coming out of the chimneys contain a lot of unburnt carbon particle. Smoke is the colloidalsolution of the solid particles such as carbon, arsenic, dust particles etc. These particles areinjurious to health and have to be precipitated . Carbon particle are charged particles and can notbe precipitated. Thus, a metal plate of oppositely charged particle is used for their precipitation. This is done bythe cottrell smoke precipitator which neutralizes the charge on the carbon particles and neutralizes them. In this way, smoke coming out of the chimneys gets free from the charged particles.

Colloid acts as a transport vector of different contaminants in water surfaces. For example, heavy  metals and radionucleides are absorbed on colloid surface and are carried throughout the water
Enzymes, which are important biomolecules in human body, freely move about in the water because of colloid action.
Colloids are used in intravenous therapy where they increase the intravascular volume and maintain a high colloid osmotic pressure in the blood

Argyrol is a silver sol and is used as an eye lotion.It is manufactured in the chemical industry to pharmaceutical grade only, using denatured pharmaceutical-grade protein for ophthalmic application and elemental silver, to produce the silver protein molecule.

Argyrol is a silver sol and is used as an eye lotion. Silver bromide, gelatin and glass plate are used in the making photographic plates.

Colloidal sols have larger surface area which provides larger sites for reactions.So,they are more effective for medical purposes.

River water contains charged colloidal particles of clay, sand and many other materials. Sea water is very big store house of a variety of electrolytes dissolved in it. As soon as river water comes in contact with sea water coagulate the suspended colloidal particles which ultimately settle down at the point of contact. Thus the level of the river bed rises. As a result, water adopts a different course and delta is formed in due course of time.

Both fluorescin and methelene blue are adsorption indicator. Both are used to show the adsorption had been taken place.

Colloidal silver has also been said to help prevent eye infections in infants when colloidal silver eye drops are used. It is also used for medical purposes including as disinfectants and microbiocides. Silver has also been added to bandages and dressings, and to the coating of medical instruments.

$AgBr$ (Silver bromide) is used in photography. The colloidal solution of it in gelatin is applied in glass plates to form sensitive plates.

Smoke particles are electrically charged colloidal particles of carbon in the air.

Colloidal sulfur is a suspension of fine sulfur particles, usually in a gum base. A good way to think about this is if one were to grind up pure sulfur and dust it into a gelatin mix before it firmed up. Colloidal sulfur is a homoeopathic 'natural' remedy used to treat skin conditions such as acne, psoriasis, eczema, and dermatitis. Colloidal sulfur can be taken orally or mixed with other ingredients and used as soap or shampoo.

Sulfur is lighter weight element and can serve as a powerful antioxidant, removing free radicals of oxygen and fluorine. Overall, colloidal sulfur is a safe substance that has been used throughout human history as a treatment for skin conditions and can be used today as an effective diet supplement.

Soap solution removes dust particles through emulsification and absorption of them.

Solid silver iodide is preferred as a nucleator for artificially stimulated rain because its crystal lattice parameters are close to those of ice, and for that reason are more effective than other salts in causing small ice crystals in clouds to melt.

To stop bleeding from an injury, Ferric chloride can be applied because of the following reason:

(A) $Fe^{3+}$ ions coagulate blood which is a negatively charged solution
(B) $Cl^−$ ions coagulate blood which is a positively charged solution

Blood being a colloidal solution, its coagulation by Hardy-Shuze's law states " Higher the charge on cation higher will be its efficiency to coagulate the colloidal solution" . Thus Option B is correct.