Advertisements
Advertisements
Question
How does the precipitation of colloidal smoke take place in Cottrell precipitator?
Advertisements
Solution
In Cottrell precipitator, charged smoke particles are passed through a chamber containing plates with charge opposite to the smoke particles. Smoke particles lose their charge on the plates and get precipitated.
APPEARS IN
RELATED QUESTIONS
Define the following with a suitable example, of each:
Multimolecular colloid
Write a note on Types of emulsion.
What are the applications of Electrophoresis?
Explain the term emulsion and types of emulsions.
Draw labelled diagram Tyndall effect.
Draw labelled diagram of Soap micelle.
Froth and whipped cream are examples of ____________.
Identify the CORRECT statement.
Which of the following statements is CORRECT?
Maximum coagulation power is in ____________.
Tyndall effect is observed due to ____________.
Tyndall effect is useful ______.
Some colloids are stable by their nature, i.e., gels, alloys, and solid foams. Gelatin and jellies are two common examples of a gel. The solid and liquid phases in a gel are interdispersed with both phases being continuous. In most systems, the major factor influencing the stability is the charge on the colloidal particles. If a particular ion is preferentially adsorbed on the surface of the particles, the particles in suspension will repel each other, thereby preventing the formation of aggregates that are larger than colloidal dimensions. The ion can be either positive or negative depending on the particular colloidal system, i.e., air bubbles accumulate negative ions, sulphur particles have a net negative charge in a sulphur sol, and the particles in a metal hydroxide sol are positively charged. Accumulation of charge on a surface is not an unusual phenomenon-dust is attracted to furniture surfaces by electrostatic forces. When salts are added to lyophobic colloidal systems the colloidal particles begin to form larger aggregates and a sediment forms as they settle. This phenomenon is called flocculation, and the suspension can be referred to as flocculated, or colloidally unstable. If the salt is removed, the suspension can usually be restored to its original state; this process is called deflocculation or peptization. The original and restored colloidal systems are called deflocculated, peptized, or stable sols.
Why does a small amount of salt have such a dramatic effect on the stability of a lyophobic colloidal system? The answer lies in an understanding of the attractive and repulsive forces that exist between colloidal particles. Van der Waals forces are responsible for the attractions, while the repulsive forces are due to the surface charge on the particles. In a stable colloid, the repulsive forces are of greater magnitude than the attractive forces. The magnitude of the electrical repulsion is diminished by addition of ionized salt, which allows the dispersed particles to aggregate and flocculate. River deltas provide an example of this behaviour. A delta is formed at the mouth of a river because the colloidal clay particles are flocculated when the freshwater mixes with the salt water of the ocean.
Colloidal solutions are stable due to ______.
How do emulsifying agents stabilise the emulsion?
On the basis of Hardy-Schulze rule explain why the coagulating power of phosphate is higher than chloride.
The coagulation of 200 ML of position sol took place when 0.73 HCL was added to its without changing the volume much. The flocculation value of HCL for the colloid is.
Which of the following is most powerful to coagulate the negative colloid?
Blood may be purified by ______.
Identify the colloidal molecule containing hydrophilic head and hydrophobic tail within it.
