An explanatory introduction about colloids

1. COLLOIDS AND
MACROMOLECUL
ES
M S . J . P R I N C E S S G R A C I A , M . S C . , M . P H I L . ,
A S S I S T A N T P R O F E S S O R O F C H E M I S T R Y
B O N S E C O U R S C O L L E G E F O R W O M E N ,
V I L A R , T H A N J A V U R

3. True Solution
Diameter of the dispersed particle
– 1 Ao to 10 Ao
Sugar or salt in water
Suspension
Diameter of the dispersed particle
– > 2000 Ao

4. DEFINITION FOR COLLOIDS
• Intermediate between true
solutions and suspensions
• Dispersed particle 10 Ao
to 2000 Ao

5. * Dispersed phase (Solute)
substance distributed
* Dispersion Medium
(Solvent)
continuous phase in which
the colloidal particles are
dispersed

6. TYPES OF COLLOIDS
Dispersed
phase
Dispersion
medium
Name Examples
Solid Solid Solid-sol Ruby glass, alloys
Solid Liquid Sol Paint, ink
Solid Gas Aerosol Smoke, haze
Liquid Solid Gel Curd, cheese
Liquid Liquid Emulsion Milk, cream
Liquid Gas Liquid aerosol Cloud, mist
Gas Solid Solid foam Cork, pumice
stone
Gas Liquid Foam Froths of air

7. Lyophilic Colloids
 Solvent loving
 Considerable affinity between phase
and medium
Lyophobic Colloids
 Solvent hating
 Very little affinity between phase
and medium

8. PREPARATION
Lyophilic sols
Dissolving in water (cold or
warm)
Lyophobic sols

9. DISPERSION METHODS

10. 1. MECHANICAL DISPERSION USING COLLOIDAL MILL

11. 2. ELECTRO-DISPERSION METHOD (BREDIG’S ARC
METHOD)

12. 3. ULTRA-SONIC DISPERSION
Using Ultra-sonic waves ( higher frequency
soundwaves)

14. 4. PEPTISATION
By the addition of an electrolyte.
Electrolyte used – peptising agent.
Ex: AgCl – HCl
Fe(OH)3 – FeCl3

15. Condensation
methods

16. By exchange of solvent
Soln. of S or P in
alcohol

poured into
water

colloidal soln.
( low solubility)

17. By change of physical state
Passing vapours through cold water
Chemical Methods

18. PURIFICATION
Dialysis
Electrodialysis
Ultrafiltration

19. DIALYSIS

20. ELECTRODIALYSIS

22. ULTRAFILTRATION

23. STABILITY OF COLLOIDS
Gold number
weight in mg of a protective
colloid which prevents the
coagulation of 10 ml of gold sol
on adding 1 ml of 10 % NaCl.

24. PROPERTIES OF COLLOIDS

25. KINETIC PROPERTY

26. OPTICAL PROPERTY

27. ELECTRICAL PROPERTY