5 ml of 1M NaCI contains NaCI = \(\frac { 1 }{ 1000 } \times \text { 5 moles = 5 millions}\) 
Thus, 100 ml of As₂S₃ sol require NaCI for complete coagulation = 5 millimoles
ஃ l L, i.e., 1000 ml of the sol require NaCI for complete coagulation = 50 millimoles
ஃ By definition, flocculation value of NaCl = 50.

"Adsorption is a phenomenon of concentration of substance on the surface of liquid or solid" (or) "The condition in which concentration of a substance in the interfacial layers between two phases is greater than in the bulk of either phase, then the substance is said to be adsorbed at the interface and the phenomenon is known as adsorption".

(i) In the manufacture of sulphuric acid by contact process SO₃ is prepared by the action of SO₂ and O₂ in the presence of Pt or V₂O₅ as a catalyst
\({ 2SO }_{ 2 }+{ O }_{ 2 }\overset { pt \ or \ { V }_{ 2 }{ O }_{ 5 } }{ \longrightarrow } { 2SO }_{ 3 }\) 
(ii) In the Haber's process for the manufacture of ammonia, iron is used as a catalyst for the reaction between Hydrogen and Nitrogen.
\({ N }_{ 2 }+{ 3H }_{ 2 }\overset { Fe }{ \longrightarrow } { 2NH }_{ 3 }\)

Various demulsification techniques are given below:
(i) Distilling of one component.
(ii) Adding an electrolyte to destroy the charge.
(iii) Destroying the emulsifier using chemical methods.
(iv) Using solvent extraction to remove one component.
(v) By freezing one of the components.
(vi) By applying centrifugal force.
(vii) Adding dehydrating agents for water in oil.
(viii) Type.
(viii) Using ultrasonic waves.
(ix) Heating at high pressures.

(i) Gold number' is a measure of protecting power of a colloid.
(ii) Gold number is defined as the number of milligrams of hydrophilic colloid that will just prevent the precipitation of 10ml of gold solon the addition of 1ml of 10% NaCl solution.
(iii) Smaller the gold number greater the protective power.