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STATE, , 8, , C, , Syllabuss, , O, , L, , L, , Differet, , O, , I, , D, , A, , OF MA, MATTER, , OF, , L, , of colloids,, systems, , Dispersed phase and, , clectrodialysis,, , dispersion, , Properties of colloidal, and, , Proper, , types,, Dialysis and, Electrophoresis, coloidal and its, solutions,, Concept of, Tyndall effect,, colloidal, movement,, of, of preparation, Brownian, and protective colloids, Nethods, colloids, Prolection, to absorption., , With, , special, , Relative, , tVpes., , 8-1., , reterene, , stability of, , hydrophobic, hydrophilic and, Application, , preparation and, , properties, , Colloidal, Concept of, 1861,, Thomas Graham in, , and, , uses,, , of, , colloids, , chemistry, , State, , on, , experiments, the basis of his, , (ii), , on d i f f u s i o n, , in different ind, , medium,, tion, , oagulation,, , Emulsion:, S., , of various substancee, , colloids., , in solution and whose co ution, which diffuse readily, substances, For example : common sait, crystalline, crystalloids., (i) Crystalloids-The, called, are, membrane, or animal, can pass through vegetable, and bases., in solution and whose solution, sugar, urea, acids, which diffuse very slowly, substances,, colloids. For example : starch, glue, gelatin, ii) Colloids-The amorphous, are called, membrane,, animal, or, cannot pass through vegetable, albumin, proteins, etc., ditferent cateyories because, and colloids are not two, crystalloids, chloride, According to modern concept,, conditions. For example : sodium, state under suitable, colloidal, into, converted, can be, the differencel., any substance, colloid in ethyl alcohol or benzene. Actually,, is, a crystalloid but it is a, solution, in aqueous, of colloids is betweenl, due to size of particles. The diameter, is, colloid, a, and, mainly, a, between, crystalloid, cm) and smallersolution (diameter 10, true, the, than, a, of, particles, are, bigger, 10 to 10 cm. These, have a range of diameter, a, of, suspension (diameter 10 cm). Thus, colloidal particles, than the particles, 10-8 cm or 10- m. thus, A°, and, m, 10nm (l10 A° to l000 A°) where nm, 100, to, nm, 1, between, It is colloidal state., colloid is not a substance but it is a state of a substance., in, , liquids, , classified as, , : (i) crystalloids, , and, , =, , 8-2. Phases of, , a, , =, , Colloidal Solution, , Colloidal solutions are hetergeneous in nature. They have two phases, , (a) Dispersed phase-It is a substance in small proportion having particles of colloiat, , n, , to 100 mm)., (b) Dispersion medium--lt is the medium in' which colloidal particles are dispersea., Thus: Colloidal Solution =, , Dispersed Phase +Dispersion Medium, , ispersed pha, A colloid is a heterogeneous system in which one substance is dispersed (dis!, ticles.have, as very fine particles in another substance called, mediun. Colloidal par, dispersion, a range of diameters between 1 nm to 100 nn.

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SIate, , Colloidal, , ofMatter, , For example: In a colloidal, is the dispersion medium., , nistinction, , 8.3. Distinction between, between, , a, , true, , True Solutions, , Property, , Size, , solution, , of particlesLess than, , (, , nm, , =, , Particles, , 2. Visibility of, , naked, , particles, , 179, , of'sulphur in water, sulphur particles make dispersed phaae and, , olution, colloidal solution, Colloidal Solutions, , nm, , Between, , 10- m)., are, , to, , and, , |Particles are, , in, , leye, , microscope., Cannot be separated, , 3. Separation of, , filtration., , solute and, , filtration., , Diffuse quickly., , Settling of, , Do not settle down, , particles, , keeping., , 7. Nature and, , Homogeneous, , stability, 8:4. Different, , and, , and 100, , Suspensions, n m., , separated by, , |Párticles are visible, , naked eye., , a, , ultrá- Can be separated by, , Ordinary filtration., ., , |Pass through, not through, , filter paper but, animal, , Diffuse slowly., , on, , |Greater than 100 nm., , invisible to naked, , can be viewed with, , by |Can, , Pass through filter, paper, and animal membrane., , 5. Diffusion, , but, , suspension, , T, , microscope., be, , solvent, , 4. Filterability, , I nm, , invisible, , eye, , arnd, , |Can, , Do not pass' through, , membrane. ordinary filter paper, , be made to settle, down, , centrifugation., , or animal membrane., , Do not diffuse., by Settle down, , stable.|Heterogeneous and unstable., , on, , their, , own under gravity., , Heterogeneous 'and, , stable., , Systems, , of Colloids, , The, , dispersed phase and dispersion medium may be solid, liquid or, gas., Depending upon the physical state of dispersed phase and, dispersion medium,, of, , ire eight types because, omogeneous mixture., , a, , gas cannot form, , a, , colloidal solution with other gas due, , colloidal solutions, , to formation of, , their, , -, , r, , Sr., , No.| Dispersed, , Dispersion, , Colloidal, , medium, , system, , Solid, , Solid, , Solid sol, , Solid, Solid, , Liquid, , Phase, , Examples, Some coloured glass and gem stones, , Paints, muddy water, starch sol, arsenious sulphide sol., , Sol, Aerosol, , Smoke, dust in air., , Gel, , Cheese, butter, jellies., , Liquid, , Gas, Solid, , Liquid, Liquid, , Liquid, , Emulsion Milk, hair-cream., , Gas, , Gas, , AerosolFog, mist, cloud, insecticide sprays., , Solid, , Solid foam|Pumice stone, foam rubber., , Gas, , Liquid, , Foam, , Soap leeher, whipped cream, Froth., , When a solid is dispersed in a liquid, this system is called sol., hen a liquid is dispersed in a solid, this system is called gel., en the dispersed, Wher, , phase and dispersion medium both are liquids, this system is called emulsion.

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Applied Chemstry, , 180, , and, is called hydrosol, sol, the, the dispersion medium is water,, alcohol, the sol is called an alcosol., , if the dispersin, , I, , 8.5. Types of Colloids, Colloids are classifed as under:, 1., , them, , Interaction, Nature of, upon, based, Classification of colloids, attracting colloids. The, solvent loving or, , Lycophilic, medium., has a great affinity for the dispersion, Examples: Starch solution, gum, gelatine. If water, , (a), , hydrophilic colloids. These solutions, them, , dispersed, , nh., , in, , colloids-These are, , are, , is used as dispersion, in nature., stable and reversible, cólloids., , solvent hating or repelling, (b) Lyophobic colloids-These are, has no affinity (love) for the dispersion medium., sols., Example: Arsenious sulphide, ferric hydroxide, called hydrophobic, If water is used as dispersion medium, they are, , medium, they are ails, , alled, , The, , coloids., , dispersed, , They, , are, , phasa, , s, , unstahla, , and irreversible in nature., Distinction between, , Lyophilic, , and, , Lyophobie sols., Lyophobic Sols, , Lyophilie Sols, , 1., , They are solvent loving sols., , 1. They are solvent hating sols., , 2., , They are reversible in nature., , 2. They are irreversible in nature., , 3, , They are self stable. Stabilising agent, required to stabilise the sol., , 4., , These sols have strong affinity between, , is not, , 3. They are unstable sols. They can be coagulated, , medium., , easily, 4. These sols have weak, , affinity, , between, , disperse, , phase and dispersion medium., , dispersed phase and dispersion, Examples : Starch sol, agar-agar, proteins.. Examples : As2S3 and Fe(OH)3, 2. Classification of colloids based on molecular size:, (a) Multi-molecular colloids-Individually the particles are not of colloidal size but they aggrega, to, , join together, , to form molecules of, , colloidal size., , Examples: Sulphur sol has a thousand or more Sg molecules., , (b) Macro-molecular colloids-In this type of colloids, the size of particles of dispersed phase, p., big enough to fall into colloidal dimension in a suitable solvent., Examples: Starch, cellulose, proteins and enzymes are macromolecules., (c) Associated colloids or micelles-These are substances which behave as normal elecrooly, at low concentration but act as coloids at higher concentration due to the formation of aggres, particles., , Examples: Soap., The temperature above, , K, , which the formation of micelle takes, temperatus, place is called Kraft temp

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fatter, , Mar, , af, , SHae, , a, , l, , o, , l, , l, , 181, , Difference between Micelles and, , Ordinary Colloids, Ordinary Colloids, , Micelles, , normal electrolytes at low|, but as olloids at, higher, , ehave as normal, Micelles, , concentration, , 1. In, , ordinary colloids, concentration does not affect, , their nature., , aoncentration., , centratohobic as well, , Theyhavelyophobic, , 2, , as, , lyophilic parts | 2. They do not have, , high conductivity., , fhey havSolution, , n, , such, , in, aggregates, , of soaps and, , water, , Methods of Preparation, , polarity., , |3. They have low, detergents in4. Examples: Solsconductivity., of starch, sulphur, (Sg), gold,, AszS3, ete., of, , Colloidal solutions, be easily prepared by, yophilic sols, mixing the dispersed phase with dispersion medium., nle:Collodal solutions of starch, gum, gelatin and egg albumin are, Example, prepared by dissolving, in hot water., le mse substances, rho colloidal solution of cellulose nitrate is obtained by dissolving it in alcohol. It is called, h, , can, , collodion., , Lwophobie sols are prepared by physical and chemical methods., , a) Physical methods, Metal, , These are Bredig's Arc method and peptisation., , ed, , ad, , Electrodes, , 1. Bredig's Are method--t is used to prepare colloidal, sol of metals such as gold, silver and platinum. This, process involves dispersion as well as condensation., In this method, electric arc is struck between metal, electrodes immersed in the dispersion medium. The, metal vapours condense to form particles of colloidal, , Electrie, arc, Dispersion, , Medium+ alkali, , -Ice-Bath, , SIZe., , ate, , 2. Peptization-It is a process of converting a freshly, prepared precipitate of ionic solid into particles of, colloidal size when a small amount of electrolyte, having a common ion is added to it., , Fig.81. Bredig's Arc Method, , For Example: When freshly precipitated ferric hydroxide, Fe(OH)3 is shaken with aqueous solution, f fric chloride, FeClh (peptizing agent), it adsorbs ferric ions, Fes* and breaks up into small sized, , alloidal particles., Cause of Peptization-Peptization, , involves the, , adsorption, , of ions of the, , electrolyte by the fine, , ICS of the precipitate., It leads to the formation of a colloidal sol., , (b) Chemical methods, , Double Decomposition--On passing hydrogen sulphide (H2S), ateh, i s oxide to form yellow colloidal solution of arsenious sulphide., , AsS3, , AsO3 +3H,S, , gas in, , an, , aqueous solution of, , +3H20, , Arsenious, , sulphide sol, , i) Oxidation-On, , passing H,S, , gas in, , alsolution of sulphur is obtained., , SO2 + 2H2S, , a, , like, dilute solution of an oxidising agent, , 3S (sol), , +2H,0, , S02,, , a, , milky

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Applied Chemistry, , 182, , ), , ride, , solution by a strOng, Reduction-On reducing of gold chloride, is formed., of, colloidal solution gold, , or. tannic, , acid,, , a, , violet, , 2AuCl3, a, , 3HCHO, , +, , 2Au, , 3H20, , (sol), , solution of, , (v) Aydrolysis-On adding dilute aqueous, is, aark red colloidal solution of ferric hydroxide, , ferric chloride, , 6HCI, dropwise, into !, ise into, , boiling water, , 3HCI, , Fe(OH)3, Ferric hydroxide sol, , Dialysis, , 87. Purification of colloidal solution, are, , stannows, , +3HCoOH +, , obtained., , FeCl3 +3H20, , Colloidal solutions, , as, , 2 A u + 3SnCl4, , 2AuCl + 3SnCl2, +, , reducing agent, ent suo, such, , purified by dialysis, , electrodialysis., , and, , soluble, , Dialysis---The method of removal of, impurities from sols by a semipermeable membrane, , Water, , bag, -, , o., , ., , Impure colloidal, , ., , .., , is, , SOlution, , ., , called dialysis., , Dialysis, , is based, , on, , the principle that sol particles, , cannot pass through parchment paper or cellophane, membrane but, , particles of true sol, , can, , pass through these, , Fig. 8.2. Dialysis, , membranes., In order to purify a solution, it is filled in a, , Addition of, , bag made up of parchment paper or cellophane, membrane. It is then suspended in fresh water. The, particles of electrolytes pass out leaving behind pure, , O= Electrolye, , O- Colloids, , Impure Sol, , =aier, Funnel, , colloid., The most important use of dialysis is the, purification of blood using artificial kidney machine., , The smal particles (ions) pass through the dialysis, , membrane and large size particles like haemoglobin, do not pass through the membrane., , Electrodialysis-The movement of ions, , Distilled, water, , Solution of, , ., , ., , Cellophane, , ., , Electrolvte, , ag, , across, , the membrane is expedited quickly by applying electric, which, electrodes., potential through, is faster than simple dialysis, is called electrodialysis., , two, , ., , The method,, , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , Fig. 8:3. Electrodialysis, , through, Electrodialysis is based on the principle that impurities being small in size, can easily passun, , the semipermeable membrane under the influence of an electric field, , 8-8. Properties of Colloidal Solutions, Colloids have heterogeneous character. They show the following types of properties, , (a) Colligative properties-Colloidal solutions show colligative properties., (b) Optical properties-Colloids show Tyndall effect., , (c) Mechanical properties-Colloids show Brownian movement., (d) Electrical properties-colloids show electrophoresis (cataphoresis)., The main properties of colloids are as under:, pOssess disper, 1. Heterogeneity-Colloidal solutions are heterogeneous in nature because they poss, , phase, , and dispersion medium.

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Colloidal State of Matter, , Size-The, , ., , diameter, , 183, , of, , particles, Filtrability-Coloidal colloidal, particles pass through10-7the, , ., , is, , vegetable or animal membrane., , ne, , 4. Adsorp, a large nu, number of, is used in, , rption-Due to thepresence, of, presence of, , 104 cm., filter, but do not pass througn, tilter paper, paper easily but, ao, , to, , unbalanced forces their surfaces, the, suspended particles to unbalanced, colloidal particles, atcorption, dyeing of cotton fabricstheir surfaces. This property, ocolloidal solution mordant. It, by treating the cloth first, as, , in froth floatati, ation, 5,, , adsorbs, , on, , the, , dye. 1t is also applicable, concentration, of, Brownian movenment-lt is the sulphide ores, random or, , rticles of the, , process, , of, , dispersed phase, , zig-zag motion, , of, , the, Cause. Brownian movement is colloidal sol., due to, , particles, , movement is, , dispersions., , on, , passed through, , hecomes, , visible., , a, , It, , /tX, , the, , Tyndall phenomenon-When a beam of, , 6., is, , irregular bombardment of the, particles of dispersed phase., responsible for the stability of colloidal, , ofthe dispersion medium, , Brownian, , of the, , light, colloidal sol, the path of, the beam, is, , Fig. 8-4. Brownian Movement, Dark, , Tyndall cone, , Colloidal solution, , called Tyndall, phenomenon., Cause. Tyndall effect is due to the, scattering of, light by colloidal particles., 7., , Electrophoresis-Particles of, , positive, , a, , colloidal sol, , negative charge. When placed in an, electric field, the colloidal particles migrate towards the, charged electrode. This movement of colloidal particlesoppositely, is called, electrophoresis or cataphoresis., , pOssess, , or, , Fig. 8-5. Tyndall Effect, , 8., , Coagulation of colloids-The process of aggregation of, particles into an insoluble precipitate by the addition of, some suitable electrolyte is called, Coagulation., colloidal, , Cause of coagulation--The particles of colloid (dipersed, phase) have positive or negative charge. When an electrolyte is, added to the sol, the colloidal particles take up oppositely charged, ions from the electrolyte. Their charge is neutralised and the, uncharged particles now come closer to form the precipitate. This, , Water, Coagulated, sol particles, , -As2, , S3, sol, , (negative charged), migrating, , sol particles, , leads to coagulation., Hardy Schulze Rule--Greater the valency of the oppositely, charged ion, more will be the coagulation of colloidal systems. Thus,, Coagulation powers of cations for negative sols like As>S3 sol, , Fig. 86. Electrophoresis, , are: Al+ > Ba2t > K*. Coagulating powers of anions for positive sols like Fe(OH)3 sol are, , FeCN)g*> PO>SO>CI., 89. Relative Stability of Hydrophilic and Hydrophobic Colloids, and albumin sol have strong aftinity between dispersed, (lyophilic) sols such as starch sol, Hydrophilic, phase and, the dispersion medium. They are quite stable. They. do not get coagulated easily. Hence they do, , O require any stabilising agent for their preservation., weak, , affinity between, , AsS3, Fe(oH)3 sols have, Hydrophobic (lyophilic) sols such medium., Therefore, hydrophobic sols are relatively less stable, nolecules of dispersed phase and dispersion, sols are relatively more stable than hydrophobic sals, an, hydrophilic sols. In other words, hydrophilic, as, , and, , the

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Applied mistry, , 184, , following factors, collolds are positively or, of hydrophobic, of, kind, electric charge. This accutively, the same, charged. All susp, Ispended colloidal particles in it have, stabilisation of the colloid.on of, causes, al, similar charges on the, t suspended particles keeps them apart and, colloids such as emulsions, the stabilit system., i) Coating of protective substances-In some., coated on the surface of don, account of the presence of a protective agent. The protective agent getS, , ne stability of colloids, , is due to the, , no, , Electric charge-The dispersed particles, , Peles, , due to, , adsorption, , on, , is stabilised., the surface and the colloid, to, of hydrophilic sol is mainly due, , Solvation-The stability, medium., Thus, a protective envelope is formed, aspersion, stable., , (in), , on, , ispersed, , solvation, , in presence, , the dispersed phase and sol, , of t, , become, , very, , 8-10. Protection and Protective Colloids, colloid, gum or gelatin Can be, solution of a lyophilic (solvent loving), The colloidal, coagulated, easily. The coagulated mass can again be redispersed to colloid form. This is why lvonhi, like starch,, , sols are also caled reversible colloids. These colloids are quite stable. When a reversible (lyophilc, colloid is added in small quantity to a comparatively unstable lyophilic sol, it imparts stability to the lece, , stable colloid., The process by which a lyophobie sol is protected from coagulation by electrolytes as a result, , of previous addition of lyophilic sol is known as protection., The lyophilic colloid used for the protection of less stable colloid is called protective colloid. For, example: gelatin acts as a protective colloid for arsenious sulphide, AsS3 sol., , Zsigmondy introudced the term gold number regarding the protective powers of different lyophilic, colloids., , Gold number is defined as the number of milligrams of protective colloids which must be, added to 10 ml of gold sol to just prevent coagulation when 1 ml of 10% NaCl solution is, added., , Smaller the gold number ofa protective colloid, greater is its protective power., Colloid, , Gold Number, , Colloid, , Gold Number, , Casein, Starch (Potato), , 0-01 -, , Gelatin, , 0-005 -0015, , Gum arabic, , 0-15 - 025, , 0-02, , 25-2, , Gelatin having smallest gold number is the best protective colloid., 8 11 Emulsions:, Emulsions are the colloids in which dispersed phase and dispersion medium both are liquias., Emulsions are of two types:, , Oil-in-water emulsion-lts dispersed phase is oil and dispersion medium is water., Examples : Vanishing cream, milk. Milk has liquid fat dispersed in water., , i, , Water-in-oil emulsion-lts dispersed phase is water and dispersion medium is oil., , Examples: Butter, cold creams, cold liver oil.

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Colloidal Stale of Matter, , 185, , Preparation of Emulsions-When a little oil is, , eion, , formed., , is, , When, , a, , ittle water is, , formed., , The, emulsion,, , an, , excess, , an, , excess of water, , of oil, water-in-O, , liquids forming emulsion will, use, separate out on keeping because, it is essential, immisC1DIe., Hence,, to add some, substance to, while, , are, , ance added,, , substa, , shaken with, , shaken with, , Soap is, , forming, , common, , a, , Isification., , is called emulsif, , ausifier acts, , as a, , an, , emulsion, , binder, , is, , oil and water, which form, , stabilize, , to stabilise, it, is called emulsifier, emulsifer. The process of, formation, of an emulsion in, The, , emulsifer gets concentrated, at the interface, between oil and, , lion, , The, , the, , emuisio, or emulsifying agent., , er, , presence ot, , an cThus, he, between oil and water., the, , water., , Properties and Applications of Emulsions, , Emulsions, , are, , very useful in our daily life., (a) Milk is an emulsion of fat in water. Butter and milk cream are, also emulsions., (b) Vanishing creams, various cold creams,, body lotions etc. are all emulsions., (c)So many medicines, ointments and paints are emulsions., (d) The cleansing action of soap and synthetic detergents for washing clothes, bathing etc. 1s Dased, on the formation of oil-in-water type emulsion., (e) Fats are digested in intestines by the process of emulsification., () Emulsions are used for the concentration of sulphide ores by froth floatation process., The colloids in which dispersion phase is a liquid and the dispersion medium in a solid, are, called gels. Examples : Cheese, jelly, curd, boot polish., Gels are hydrophilic colloidal solutions., , 812.Applications of colloidal solutions, () Purification of water-When alum is added, to muddy water, the negatively charged clay particles of, , Coagulated séwage, , Sewage sol, , the colloid are neutralized by Al* ions from alum., Therefore, the mud particles settle down due to Anode i, C0agulation and water is filtered and used., , -Cathode, , i) Sewage disposal-Colloidal particles of dirt, eC. carry electric charge. On passing the sewage through, , Fig. 8-7. Sewage disposal, , metallic plates kept at high potential, the colloidal, , parti les move towards the oppositely charged, lectrode and are precipitated. Sewage water is,, , High voltage wire, , (electrode), , thus, purified, Gii) Smoke precipitation-Smoke, ontains colloidal particles of carbon in air. Smoke, particles are electrically charged. Cottrell's, , is used to precipitate the particles of, pitator, carbon in smoke., , Smoke, chambe, having, , from, a, , chimneys, , is, , air, , Smoke, , Precipitated ash, , passed through, plates, , number of metallic, , charged electrode and get precipipated. As aresu, purified, , carbon particles, , a, , Connected to a urce of high potential. Charged, particles of smoke are attracted to the oppositely, not, , Chimney, Gases free from, , passes, , out., , Fig.88. Cottrell Smoke Precipitator

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186, , Applied Chenistry, (iv))Delta formation-Delta is formed due to coagulation of negatively charged clay particlespres, , v e r water by the positively charged ions prescnt in Sea watcl., , Na+C Na+C, , Na+C, , Delta, , Sea, , Negatively charged, particles of sand, , River, , Fig. 8-9., , Delta Formation, , Some applications of colloids in our day to day life are, (a) Blue colour of sky-lt is due to colloidal dust particles floating about in the sky. These particles, scatter blue light that makes the sky appear blue. The sky would have appeared dark throughout in the, absence of colloidal dust particles., (b) Clotting of blood-Blood is a negatively charged colloidal solution. On applying FeCl solution,, , bleeding stops due to coagulation and the clotting of colloidal particles of blood takes place., (c) Photography-In photography, photosensitive plates are formed by applying a colloidal solution, of silver bromide (AgBr) in gelatin on glass plate or celluloid film., (d) Rubber plating-Latex is a colloid solution of negatively charged rubber particles. On making, the object to be rubber plated as anode in the rubber plating bath, negatively charged particles of rubber, , move towards the anode and get deposited on the object., , LSummary, , Important Points to Keep in Memory, , 1., , Colloidal particles have a range of diameters between 1 nm to 100 nm (1 nm = 10-9 m)., , 2., , Sols are colloids of solids in liquids. Alloys are colloids of solids in solids, Gels are colloids of liquids, in solids. Emulsions are colloids of liquids in liquids., Lyophilic colloids are solvent loving. They are also called reversible colloids., , 4., , Lyophobie colloids are solvent hating. They are also called irreversible colloids, , 5., , True solutions are homogeneous while colloidal solutions are heterogeneous in nature., , 6. Colloidal solutions have two phases: dispersed phase and dispersion medium., 7., 8., , Soaps (C7H3sCOONa, sodium stearate) and detergents are associated colloids., rong, Associated eolloids or micelles are the substances which at low concentrations behave as normal strong, electrolytes but at higher concentrations show colloidal behaviour due. to the formation of aggregate, particles., , 9. Particles of sols possess positive or negative charge. Arsenious sulphide, As2S3 sol is1negatively charged, 10., , whereas ferric hydroxide, Fe(OH)3 sol is positively charged., When placed in an electric ield, the movement of colloidal particles towards the, or cataphoresis., electrode is called electrophoresis, , 11,, , Brownian movement is he random or zig-zag motion of colloidal particles., , oppositely charged