the Collidal state

THE COLLIDAL STATE



HISTORY OF COLLOIDAL SOLUTION:

• The colloidal state was introduced by Thomas Graham first time in 1861AD.
• He made an experiment on the substance like sugarcane, urea, sodium chloride, glue, gelatin and gum Arabic etc
• And he observed that the substance like sugar cane, urea and sodium chloride passes rapidly through parchment membrane, and some substance like gum, gelatin and glue passes through membrane or doesn’t pass. slowly.
• Hence this difference made colloidal state to become one of the major  part of studies in Physical Chemistry.

CLASSIFICATION OF COLLIDAL

 Based upon the rate of diffusion through parchment membrane, Graham classified into two types.

• CRYSTALLOIDS
• COLLOIDS

i. CRYSTALLOIDS:

• The word crystalloid means crystal like. (Crystal + Iodos = crystal like)
• This states are crystal in nature.
• In this state the solution rapidly diffuse through parchment membrane.
• I.e. Sugar, glucose, urea, inorganic salt, acid and base etc.

ii..COLLOIDS

• The word colloids mean glue like. (Kolla + Iodos = glue like)
• In this state, the solution slowly diffuse through the parchment membrane.
• I.e. . Gelatin, glue, albumin, starch, silicic acid etc…

But later Graham relise that, his classification doesn't satisfy to all substance, based upon the rate of diffusion. Because he observed,

• Sodium Chloride acts as crystalloids in water but colloids in benzene.
• Soap acts as colloid in water but crystalloid in benzene.

So based on the observation of his experiment, he concluded that Any substance, regardless of its nature, could be converted into colloid by sub-dividing it particle of colloidal size.

COLLOIDAL STATE :

CHARECTERISTIC OF COLLOIDAL STATE:

•  The colloidal solution appears to be homogeneous to our eyes, but it appears to be heterogeneous under an ultra-microscope.
• It is intermediate between true and suspension solution.
• It is also known colloidal dispersion.
• The Colloidal particle passes rapidly through filter paper and slowly diffuse through parchment paper.
• This particle is invisible because it’s size is half to the smallest wavelength of visible radiation.
• There is no effect of gravity on particle motion.
• Some of the colloidal particle is best in self stabilizing because this substance keep the colloidal particle far away and prevent the growth of colloidal particle.
• It can be defined as a heterogeneous dispersion of two immiscible phases (dispersed phases and dispersion phases).

DISPERSED PHASE + DISPERSION MEDIUM = COLLOIDAL SOLUTION

Phase no.1- DISPERSED PHASE :

• It is constituent by that substance whole particles are in dispersed in 2nd phase.
• The substance distributed as a particle is called as dispersed phase.
• This particle has a definite colloidal range. (1- 200nm).
• The particles are larger then the ordinary molecules.
•  It is also known as discontinuous phase or inner phase.
• The particle of dispersed phase is known as colloidal particle.

Phase no.2- DISPERSION MEDIUM :

• This phase provides medium for dispersion.
• This phase consists of continuously inter linked molecules.
• This phase is also known as continuous phase or outer phase or external phases.

The above characteristic are listed based upon the observation of ZSIGMONDY (1903) under the micro scope.

GENERAL CLASSIFICATION OF COLLOIDS:

The above characteristic shows that colloidal particles have various characteristics. As a result, it is divided into many types according to perceptions.

• Based upon the physical state of Dispersed phase and dispersion medium.
• Based upon the affinity of Dispersed phase and dispersion medium. 
• Based upon the types of particle in dispersed phase.

a. CLASSIFICATION- BASED UPON THE PHYSICAL STATE OF DISPERSED PHASE AND DISPERSION MEDIUM:

Based upon the physical state of Dispersed phase and dispersion medium, it is classified into mainly 8 types.

SL.NO	SOLUTE	SOLVENT	EXAMPLE
1.	Solid	Solid	Alloys
2.	Solid	Liquid	Sugar in water
3.	Solid	Gas	Smoke
4.	Liquid	Solid	Cheese
5.	Liquid	Liquid	Milk
6.	Liquid	Gas	Cloud
7.	Gas	Solid	Cork
8.	Gas	Liquid	Soda Water

NOTE:

 Gas- Gas in not a part of colloids because it exits in homogenous mixture. 

b. CLASSIFICATION- BASED UPON TYPES OF PARTICLE OF THE DISPERSED PHASE AND DISPERSION MEDIUM:

          Based upon types of particle size the colloidal is classified into 3 types.

• Multimolecular colloids
• Macromolecular colloids
• Associated colloids

 1.MULTIMOLECULAR COLLOIDS:

• Multimolecular colloids are formed when a large number of atoms or small molecules of a substance aggregate together during dissolution to form species with colloidal sizes.
• In this sort of colloidal system, the dispersed phase contains huge aggregates of atoms or molecules that form as a result of the dispersed particle's aggregating characteristics

2.MACROMOLECULAR COLLOIDS:

• When a substance with large molecules, known as macromolecules, dissolves in a suitable liquid, the molecules of the substance create a solution. i.e the dispersed particle have size in the colloidal range.
• Hence those substance are called as macro molecular colloids.
• i.e. Starch, cellulose, gelatine, Protein, polyethene, nylon, polystyrene, rubber
• Because these molecules are big and have diameters equivalent to colloidal particles, their dispersions are referred to as macromolecular colloids.

3.ASSOCIATED COLLOIDS- MICELLES:

• Associated colloids are substances that, when dissolved in a medium, function as regular, strong electrolytes at low concentrations but, at larger concentrations, display colloidal state qualities due to the production of aggregated particles.
• Hence that aggregated particle are known as micelles.

NOTE:

Micelle formation is only possible at a specific temperature and above a specific concentration. As a consequence, that temperature is known as the Kraft Temperature, and that concentration is known as the Critical Micelle Concentration.

c. ON THE BASIS OF AFFINITY OF DISPERSED PHASE AND DISPERSION MEDIUM: (SOLS)

AFFINITY – The degree to which a substance tends to combine with another.

Sols are colloidal systems that consist of solids (dispersed phase) dispersed in liquid (dispersion medium). On the affinity differential between the dispersed phase and the dispersion medium. It is classified into two types: They are.

• Lyophilic
• Lyophobic

I. LYOPHILIC:

We can also say that these colloids are solvent loving (Lyo - solvent: Philic - loving).

• The colloidal system in which the dispersed phase has a definite affinity toward the dispersion medium or solvent is known as lyophilic.

i.e., dispersion of starch, gum, protein in water.

• This substance is easily formed by bringing dispersed phases closer to the dispersion medium.
• These sols are also known as emulsoids or intrinsic sols.
• Based upon the consideration of solvent (dispersion medium), they are termed as following
• Water- hydrophilic
•  Benzene – Benzophilic
• Alcohols – alcohophilic
• When the particles are dissolved, these colloids are precipitated or coagulated only by larger concentrations of electrolytes
• These colloids are reversible by mixing the evaporated or congulated medium with the dispersion medium.
• The particle of hydrophilic sol may have little or no chare at all.
• This particle doesn’t scatter light and there is no tyndall effect because it is relatively small particle size.
• These particles migrate to an anode or cathode or not at all, when they are placed in an electric field.
• The viscosity of these particles is higher than the dispersion medium and is set to a gel by cooling the warm solution.           i.e., hydration of gelatin.

II. LYOPHOBIC:

• We can also say that these colloids are solvent hating (Lyo - solvent: Phobic - hating).
• The colloidal system in which the dispersion phase has less affinity toward the dispersion medium or solvent is known as lyophobic.
• It does not solvate easily.
• Even at low electrolyte concentrations, these colloids precipitate due to the absence of a protective layer.
• It is an irreversible sol—once precipitated, it cannot be reconstituted by mixing in dispersion media.
• These sols are also known as suspensoids or extrinsic sols.
• If water is the dispersion medium, then it is known as hydrophobic colloids.

I.e. dispersion of gold, sulphur and iron(III) hydroxide in water.

•  The particles of hydrophobic sol carry positive or negative charge, which gives the stability.
• These sols show the tyndall effect because they are large enough to scatter light.
• These particles move either to the anode or cathode, depending on whether they carry a negative or positive charge.
• The viscosity of these particles is similar to the dispersion medium and doesn’t form a gel.

APPLICATION OF COLLOIDAL 

Colloids are important in our daily lives and in business. As a result, everyone should be aware of its various applications. This gives many important products which make life easier to move without struggle.

Some of the vital applications are

FOOD:

Many of our foods are colloidal in nature.

i.e.

• Ice cream is the dispersion of ice in cream.
• Bread is the dispersion of air in baked dough.
• Milk is the emulsion of butterfat in water protected by protein, casein, etc.

MEDICINE:

The majority of medicines are used in colloidal form because it is easier to absorb and assimilate. The majority of drugs are water soluble. 

i.e

• Argyrol—
• S-sol
• Milk of magnesia
• List of antibodies suitable for injection
• Penicillin
• Streptomycin

DETERGENTS:

One of the most important uses of colloids is the manufacturing of soap and detergent.

• Soap is an electrolyte in nature, so it absorbs dirty particles and washes them away.
• Detergents: lyophilic colloids

RAIN:

•  Hence, the cloud is one of the particles of colloids. 
• It is one of the classifications based upon the physical state (liquid + gas). 
• Clouds are colloidal droplets that condense in cooler regions, resulting in rainfall. 
• Sometimes, oppositely charged clouds undergo mutual coagulation and form raindrops, which results in rainfall. 
• By spraying electrified sand of the opposite charge to the cloud from an aeroplane, we can create artificial rainfall. 

WATER TREATEMENT;

• It also plays an important role in water treatment. 
• Currently, almost 25 % of the world’s population is unable to drink fresh water. 
• Colloidal particles can be found in water that has been collected from natural sources. 
• To purify the water for drinking, these particles are coagulated and removed.

The method involved in purification

• The sol particles are negatively charged.
• The addition of aluminium sulphate to water results in the formation of hydrated aluminium hydroxide.

Al³⁺   +   3 H₂O  ®        Al(OH)₃   + 3H⁺

• The positive floc coagulates the negative sol particles which settle down and finally the water gets purified.

Al(OH)₃   + H⁺  +   3 H₂O  ®        Al(OH)₃ (H₂O)⁺₄

RUBBER

The latex's negatively charged rubber particles are deposited on the wares and handles of various tools. Rubber gloves are formed by rubber plating on suitable templates. 

 

 

CLEANING SMOKE FROM COMPANY:

• In most industries, the smoke is released without filtration into the air without any filtration.
• The smoke is one of the colloidal dispersions.
• By following the Campbell Precipitator Method, the solid particles of smoke can be removed before they are released into the air.

DELTA FORMATION:

• River water consists of colloidal particles like sand and clay, which carry a negative charge, while sea water carries a positive charge. 
• Finally, when they meet together and result in the precipitation of the delta 

THE NANOTECHNOLOGY:

By using reverse micelles, nano-sized materials are prepared for use as catalysts. 

 

METALLURGY:

The metal sulphide ore is concentrated by the flotation process, which involves the treatment of the pulverised ore in an emulsion of pine oil.

ROAD CONSTRUCTION:

Asphalt in water emulsion is used for building roads without the necessity of melting the asphalt.