山东大学：《物理化学》课程教学资源（讲义资料）8.8.1 Optical property of colloids

8.8 Properties of colloids Out-class reading Levine pp 402-405 13.6 Colloids

8.8 Properties of colloids Out-class reading: Levine pp. 402-405 13.6 Colloids

8.8.1 Optical property of colloids (I)Tyndall effect ol olution 1857, Faraday first observed the optical properties of Au sol 1871, Tyndall found that when an intense beam of light is passed through the sol the scattered light is observed at right angles to the beam Tyndall effect particles of the colloidal size can scatter light Distinguishing true solutions from sols

1857, Faraday first observed the optical properties of Au sol. sol solution Dyndall Effect: particles of the colloidal size can scatter light. (1) Tyndall effect 1871, Tyndall found that when an intense beam of light is passed through the sol, the scattered light is observed at right angles to the beam. 8.8.1 Optical property of colloids Distinguishing true solutions from sols

8.8.1 Optical property of colloids (I)Tyndall effect

(1) Tyndall effect 8.8.1 Optical property of colloids

8.8.1 Optical property of colloids (2)Rayleigh scattering equation 9丌2p 1=102242(n2+2ni +cos e Discussion (1) (2)v(concentration) ()r(distance) 4)2 6)6

(2) Rayleigh scattering equation: Discussion: (1) V (2) v (concentration) (3) r (distance) (4)  (5) n (6)  (  )   1 cos 2 2 9 2 2 1 2 2 2 1 2 2 4 2 2 2 0 +         + − = n n n n r vV I I  8.8.1 Optical property of colloids

8.8.1 Optical property of colloids (2)Rayleigh scattering equation Applications CP2 I= K 1. Colors of scattering and transition light 2. Influential factor for scattering intensity 3. Determine particle size and concentration 4. Red light for alarming

4 2  cV I = K Applications 1. Colors of scattering and transition light 2. Influential factor for scattering intensity 3. Determine particle size and concentration 4. Red light for alarming (2) Rayleigh scattering equation: 8.8.1 Optical property of colloids

8.8.1 Optical property of colloids (3 Ultramicroscope Fig. L. The first arrangement for making ultramicroscopic particles visible Theoretical visibility: 0.2-0.36um principle of ultramicroscope The amplification: 1000 1925 Noble prize Germany, austria, 1865-04-01-1929-09-29 Colloid chemistry(ultramicroscope)

Richard A. Zsigmondy (3) Ultramicroscope 1925 Noble Prize Germany, Austria, 1865-04-01 - 1929-09-29 Colloid chemistry (ultramicroscope) principle of ultramicroscope 8.8.1 Optical property of colloids Theoretical visibility: 0.2-0.36 m The amplification: 1000

8.8.1 Optical property of colloids (3)Ultramicroscope Fig. 2. Immersion ultramicroscope L= Light source: F= Telescope objective which gives a picture of the light source on the precision slit PrSp. The condenser B forms an image of the precision slit in the col- lodal solution, which is in a small The pictures reproduced from the Nobel Prize report 1): Particle size: For particles less than 0. 1 um in diameter which are too small to be truly resolved by the light microscope, under the ultramicroscope, they look like stars in the dark sky

1): Particle size：For particles less than 0.1 m in diameter which are too small to be truly resolved by the light microscope, under the ultramicroscope, they look like stars in the dark sky. The pictures reproduced from the Nobel Prize report. (3) Ultramicroscope 8.8.1 Optical property of colloids

8.8.1 Optical property of colloids (3 Ultramicroscope 2)Particle number can be determined by counting the bright dot in the field of version 3) Particle shape is decided by the brightness change when the sol was passing through a slit Slit-ultramicroscope Filament, rod, lath, disk, ellipsoid

Filament, rod, lath, disk, ellipsoid 2) Particle number can be determined by counting the bright dot in the field of version; 3) Particle shape is decided by the brightness change when the sol was passing through a slit. Slit-ultramicroscope (3) Ultramicroscope 8.8.1 Optical property of colloids