The Preparation of Colloid and

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The Preparation of Colloid and Electrophoresis
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Content

• Purposes and Demands
• Principle
• Apparatus and Reagent
• procedure
• Data Records and Processing
• Questions
• Attentions
• Demonstration
•  

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Purposes and Demands

• Command the principle and technique of
  electrophoresis used to determine ? potential.
• Determine ? potential of Fe(OH)3 colloid by
  electrophoresis method.

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Principle

• Nearly all the colloid is electriferous. When
  colloid is in an electric field, electriferous
  particles would move to certain direction and
  this phenomena is called electrophoresis.

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• There are three reasons why colloids are
  electriferous.
• Firstly, Colloids ionize or adsorb ions. Other
  reason is that triboelectricity is generated by
  friction between colloids and disperse medium.
• Eletric potential difference between colloids
  and disperse medium is called ? potential.

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• Obviously, in a electric field, colloidss
  motion speed is related to? potential, which is
  also called electrokinetic potential.
• Besides, instability of colloidss coagulation
  is related to ? potential. So, ? potential is
  very important for us to acquire properties of a
  colloid.

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• Given same eletric field and temperature,
  there is a relationship between moving rate U of
  colloid and ?

Where ? is viscosity of medium, L stands for
distance between two electrodes and e is
dielectric constant of medium.
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• We shall be concerned with the moving boundary
  method to determine electrophoretic rate. If
  boundary between colloid and solution take t time
  to move distance l, we obtain
• Ul/t

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• and, Eq. ? can be written in the form
• ?(?ll')/(eVt)
• Where l, l, t and V can be determined towards
  the experiment, ? can be looked up from appendix
  and e can be figured out from the following
  formula

T is thermodynamic temperature.
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Apparatus and Reagent

• Electrophoresis detector
  
• Direct-current main
• Stopping-watch
• Funnel 1
• Conductivity detector
• FeCl3 (0.1M)
• NaCl

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Procedure

• 1.     Preparation of pure Fe(OH)3 colloid.
• Mete about 65 ml of Fe(OH)3 solution and heat
  it nearly to boiling point. After the colloid is
  cooled to room temperature, distribute it into
  two osmotic bags,

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• put bags in beaker which is full of distilled
  water and make sure that the colloid is immersed
  in liquid entirely. Exchange distilled water
  three times and a time per 20 minutes.

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• 2.Determination of the electrophoresis speed U
  and potential grads
• a.Wash the electrophoresis detector with
  chromic acid. Scrawl the stopcock with vaseline.
• b.Confect NaCl solution of which conductivity
  is equal to Fe(OH)3 colloid.

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• C. With a funnel transfer colloid to U tube
  until the level is above o scale, turn off the
  stopcock and then pour out splith left in U tube.
  Add NaCl liquor to two arms of U tube until the
  level is about 15 cm in height.

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• Carefully and slowly revolve the stopcock and
  make a clear boundary place between the two
  liquids. Put two electrodes into two arms of U
  tube and make sure that the electrodes height in
  liquids are the same.

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• b. Set direct-current main at 30V-50V. Mark
  down the position of boundary. Take records per
  10 min.
• d. Mete the distance between two electrodes 3-5
  times and figure out an average value. (It is not
  the horizontal distance)

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Sketch-maps of Equipments
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• Data Records and Processing
• Kinds of colloid
• ?0.001002PaS
• Time of eletrophoresis
• Voltage
• Distance between two electrodes
• Moving distance of boundary
• Rate of colloid
• ?
• What charge did the colloid carry?

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Questions

• 1.What factors does the colloid motion speed
  depend on?
• 2.Whats the result if the electrophoresis was
  not wash cleanly and some electrolyte stay on
  tube wall.
• 3.Why should conductivity of NaCl liquor be
  close to the colloids?

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Attentions

• 1.Colloid need to be osmosized as possible as
  pure.
• 2.Conductivity of the assistant liquor is closed
  to colloids.
• 3.Operate carefully and make sure the boundary
  is clear.

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