日一句 王蒙:书好比是前人走过的脚印。读书有 个最大的问题,就是通过书本去发现生活, 去解释生活,去推动生活,而不是就书论书
王蒙：书好比是前人走过的脚印。读书有一 个最大的问题，就是通过书本去发现生活， 去解释生活，去推动生活，而不是就书论书。 一日一句
8.8.2 Dynamic properties of colloids (4)ultracentrifuge b) Differential Centrifugation Density Gradient Centrifugation Time(min) Time( min) Speed (RPM) Speed (RPM bvIrus A eel Virus B Virus A irus B
(4) ultracentrifuge: 8.8.2 Dynamic properties of colloids
8.8.2 Dynamic properties of colloids (4)ultracentrifuge: For sedimentation at equilibrium Centrifuge acceleration: a=0 x dc( mr F=oxM (1-vpo)dx RT Fi=oxO=MvPoox 2RTIn M F=M1(1-vP0)2x (1-v0)2(x2-x v specific volume Relative centrifugal force. RcF rTdc rt dc dhl dxl c a8=0xlg
(4) ultracentrifuge: Centrifuge acceleration: a x 2 = r 2 Fc = xM F xM M v x b 2 0 r 0 2 = = For sedimentation at equilibrium v dx RT M x c dc (1 )0 2 r = − 8.8.2 Dynamic properties of colloids d = d d RTdc RT c f cdhL xL c = v specific volume 2 c r 0 F M v x = − (1 ) (1 ) ( ) 2 ln 2 1 2 2 2 0 1 2 r v x x c c RT M − − = 2 a g x g / / = Relative centrifugal force, RCF
8.9 Stability and coagulation of colloids After Before
8.9 Stability and coagulation of colloids
8.9.1 Stability of colloids Why the colloidal system is quite stable? (1)Dynamic stabilization: Brownian motion and diffusion prevent colloidal particles from sedimentation. The less, the more stable. (2) Electric stabilization: All the colloid particles possessing the same charge tends to repulse each other and keep the colloid from coagulation (3)Solvation shell: The interaction between particle and solvent also helps to prevent aggregation of colloidal particles on collision How can we destroy the stability of a colloid?[Group discussion and share What is the role of stabilizing agent in preparation of colloids? Ag-Na, co Chinese ink--gelatin
Why the colloidal system is quite stable? (1) Dynamic stabilization: Brownian motion and diffusion prevent colloidal particles from sedimentation. The less, the more stable. (2) Electric stabilization: All the colloid particles possessing the same charge tends to repulse each other and keep the colloid from coagulation. (3) Solvation shell: The interaction between particle and solvent also helps to prevent aggregation of colloidal particles on collision. 8.9.1 Stability of colloids How can we destroy the stability of a colloid? [Group discussion and share] What is the role of stabilizing agent in preparation of colloids? Ag-Na2CO3 ; Chinese ink—gelatin