Definitions

ELECTRICAL DOUBLE LAYER AND ZETA POTENTIAL

  ELECTRICAL DOUBLE LAYER AND ZETA POTENTIAL The surface of colloidal particles acquires a positive or negative charge by selective adsorption of a layer of positive and negative ions around it. This layer attracts counter ions from the medium which form a second layer of opposite charges. The combination of two layers of positive and negative charges around the sol particles ...

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THE BROWNIAN MOVEMENT

THE BROWNIAN MOVEMENT   Robert Brown in 1927 observed that pollen grains when placed in a liquid and seen through a microscope show a zig-zag motion. He also found that colloidal particles present in a sot. show the same type of motion. This random zig-zag motion of the colloidal particles is known as Brownian movement. This movement is caused when ...

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Tyndall effect & Tyndall cone

Tyndall effect & Tyndall cone The colloidal solution shows the property of scattering of light. When light is passed though a colloidal solution, the rays are scattered. This phenomenon of scattering of light by colloidal particles present in the sols was first studied by Tyndall and is known as the Tyndall effect. The bright cone of scattered light is called Tyndall cone. When a beam ...

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ELECTRO-DISPERSION OR BREDIG’S METHOD

ELECTRO-DISPERSION OR BREDIG’S METHOD This method involves both dispersion and condensation processes. In this method, an electric arc is produced inside water (solvent) between the two electrodes of the metal to be dispersed. The heat of the arc evaporates the metal. These vapours of the metal are condensed by the ice cold water to form a colloidal solution. A small ...

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HYDROPHILIC SOLS & HYDROPHOBIC SOLS

HYDROPHILIC SOLS The lyophilic sols are called hydrophilic when water is used as the medium. HYDROPHOBIC SOLS The lyophobic sols are called hydrophobic when water is used as the dispersion medium.

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LYOPHILIC SOLS (SOLVENT LOVING) & LYOPHOBIC SOLS (SOLVENT HATING)

LYOPHILIC SOLS (SOLVENT LOVING) These are the colloidal solution in which the dispersed phase shows a definite affinity for the dispersion medium or the solvent, when lyophilic soles are precipitated  they can easily be converted back into soles by addition of the dispersed medium. Hence are also called reversible soles and behave like true solutions to sonic extent. They are ...

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CHEMICAL ADSORPTION OR CHEMISORPTION

CHEMICAL ADSORPTION OR CHEMISORPTION It is the adsorption in which molecules of the adsorbate are held to the surface of the adsorbent by chemical bond which may be covalent or ionic. Chemisorption is thus highly selective since only certain types of molecules will be adsorbed by a particular solid. This depends on the chemical properties of gas and the adsorbent. ...

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PHYSICAL ADSORPTION OR PHYSISORPTION OR VAN DER WAALS ADSORPTION

 PHYSICAL ADSORPTION OR PHYSISORPTION OR VAN DER WAALS ADSORPTION It is the adsorption in which molecules of the adsorbate are held to the surface of the adsorbent by weak Vander Waal’s forces. Thus physical adsorption has tow heat of adsorption of the order of 5 to 10 kcal per mole of the gas. A rise in temperature will increase the kinetic ...

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Near,Middle/ Fundamental & Far Infrared Region

(1)  NEAR INFRARED This region extends from 0.75 to 2.5 micro meter, with wave- numbers 12,500- 4000 c/m. In this region majority of the absorption bands are due to overtones of hydrogen stretching vibrations. (2)  MIDDLE OR FUNDAMENTAL INFRARED This region extends from 2.5 to 16 micro meter with wave numbers 4000- 625 c/m. Molecular vibrations and rotations take place ...

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Hypsochromic Shift /blue shift & Bathochromic Shift /red shift

Hypsochromic Shift /blue shift & Bathochromic Shift /red shift (1)   If the group is more polar in the ground state than in the excited state, the non- bonding electrons in the ground state are relatively stabilized by hydrogen bonding or due to electrostatic interaction with the polar solvent. As A result, the absorption is shifted to shorter wavelength with increasing solvent polarity. ...

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