88.8 Electric properties of colloids
§8.8 Electric properties of colloids
8.8.1 Electrokinetic phenomenon of colloid (I)Electropho the motion of colloidal particles under the action of an electric field sands (2) Electro-osmosis the motion of dispersion medium The experiments done by PeNce in 1809 under electric field demonstrated that both colloidal particles and dispersion medium are charged and can move under electric fields The colloidal particles of clay is negatively charged A colloidal particle may has hundreds of charge
The experiments done by PeNcc in 1809 demonstrated that both colloidal particles and dispersion medium are charged and can move under electric fields. The colloidal particles of clay is negatively charged. A colloidal particle may has hundreds of charge. 8.8.1 Electrokinetic phenomenon of colloids (1) Electrophoresis: the motion of colloidal particles under the action of an electric field. (2) Electro-osmosis: the motion of dispersion medium under electric field
8.8.2 The charge of colloids (1) Positively charged sols 3)Some sols, such as AgI sol, can be metallic oxide sols. metallic either positively charged or negatively hydroxide sols and some dyes harged depending on the preparation (4)Some lyophilic sols(protein solution) (2) Negatively charged sols: metal, metallic sulphide, sulfur can be positively, negatively or neutrally charged depending on the ph and the clay, paper, silicic acid colloids
(1) Positively charged sols: metallic oxide sols, metallic hydroxide sols and some dyes. (2) Negatively charged sols: metal, metallic sulphide, sulfur, clay, paper, silicic acid. (3) Some sols, such as AgI sol, can be either positively charged or negatively charged depending on the preparation. (4) Some lyophilic sols (protein solution): can be positively, negatively or neutrally charged depending on the pH and the colloids. 8.8.2 The charge of colloids
8.8.3 Origination of charge (I)Ionization and unequal dissolution: proteins Silica sol: H, SiO3=2H*+ SiO3 OH R-CH-COOH clay, glass, soap, biological R-CH-CO0 2R-CH-CO0 NH NH3 NH, macromolecules Agl sol: dissolution of Agt is more readily The pH at which protein does not move than that of i under electric field is named as isoelectric point
(1) Ionization and unequal dissolution: Silica sol: H2SiO3 = 2H+ + SiO3 2- clay, glass, soap, biological macromolecules AgI sol: dissolution of Ag+ is more readily than that of Iproteins The pH at which protein does not move under electric field is named as isoelectric point. 8.8.3 Origination of charge
8.8.3 Origination of charge (2)Adsorption Agl sol: AgNO3+ KI: Agt, I,k, NO3- Agl, when prepared by adding ki into dilute AgNO, solution, positively charged AgI sol can be prepared. When adding AgNO3 into KI (AgI)m solution, negatively charged Agl sol was btained Fajans rule of preferential adsorption Co-ions/similiions: counterions Sols preferentially adsorb ions comprising itself, and then the ions with higher charges
AgI, when prepared by adding KI into dilute AgNO3 solution, positively charged AgI sol can be prepared. When adding AgNO3 into KI solution, negatively charged AgI sol was obtained. Fajans rule of preferential adsorption AgI sol: AgNO3 + KI: Ag+ , I− , K+ , NO3 − Sols preferentially adsorb ions comprising itself, and then the ions with higher charges. Co-ions /similiions; counterions (AgI)m I - I - I - (2) Adsorption 8.8.3 Origination of charge