Determination of the Specific Surface

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Determination of the Specific SurfaceSolution
Adsorption ??
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Contents

• Purposes and Demands
• Principle
• Apparatus and Reagent
• Procedure
• Data Records and Processing
• Questions
• Attentions
• ??

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Purposes and Demands
1.Understand the principle of
solution adsorption method. 2. Learn how to
determine the specific surface of micro-silica
gel by the adsorption method with methylthionine
chloride solution.
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Principle

• The specific-surface that stands for general
  surface of 1 g solid is an important
  characteristic parameter of porosity powder
  substance. It did good job in fields of
  manufacture such as catalyze, chromatogram,
  environmental protection and spinning and
  scientific research.

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• We determine the specific surface of micro-silica
  gel with the method of methylthionine-chloride
  solution adsorption, since the tendency of
  methylthionine chloride to be adsorbed by most of
  the solid is the largest in dyestuffs which had
  been found.

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• It presents the monolayer adsorption which is
  coincident with the Langmuir adsorption
  isotherm.

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• As stated in monolayer adsorption theory, when
  the admolecules cover full on the surface of
  adsorbent, the area of 1g adsorbent seized by
  admolecule is that the admolecules number is
  multiplied by the area of an adsorbed molecule.

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The total area of the solid is
Where S, A, M , NA, W, ?W, are respectively, the
specific surface with( cm2/g), the
cross-sectional area of methylthionine-chloride
molecule( 81.310-16cm2),
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• the molar mass of methylthionine-chloride(
  373.9), Avogadro constant, the mass of silica
  gel(g) and the mass of methylthionine-chloride
  when silica gel comes to the saturated adsorption.

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• It is important to select a substance which has
  the quite large specific surface in the
  experiment.
• Methylthionine-chloride has two adsorption peaks
  in the visible light wavelength of 445nm or
  665nm.

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• We Determine the absorbance change in
  solution by the 722 type of spectrophotometer on
  the foundation of the equation below

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Where C0 is the primary concentration of the
solution, C is the concentration of the saturated
solution after adsorption and V is the volume of
solution.
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Apparatus and Reagent

• 722-spectrophotometer 1
• Conessi-oscillator 1
• Volumetric flask(100ml) 8
• Iodine measuring flask(100ml) 1
• Spheric aspirator 1
• Pipette(10ml, 25ml, 50ml) 3
• Methylthionine-chloride solution(50010-3mg/ml)
• micro-silica gel

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Procedure

• 1. Determination of the specific surface
• ? Prepare the Methylthionine-chloride solution
  of 5010-3mg/ml for reservoir liquor.
• Pipette the 10ml liquid of 5010-3mg/ml to a
  100ml volumetric flask and make up this solution.

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• ? Pipette the 50ml solution to a iodine
  measuring flask and add 50mg of silica gel,then
  surge it for half an hour. Pipette 25ml of this
  solution and make up other solution in a 100ml
  volumetric flask ,then determine the absorbance
  and look up the concentration C' from the
  standard curve.

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Protract of standard curve.

• Pipette the reservoir solution of respectively 1,
  2, 3, 4, 5 and 6ml to six 100ml of volumetric
  flasks and make up the terms of concentration of
  standard solution. Determine the absorbance of
  those solution at the biggest absorption
  wavelength of 445nm or 665nm.

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Data Records and Data Processing

•    Look up C' from the standard curve based on
  the absorbance by the step 1 and 2.
• Figure out the values of C according to the
  relation of C' and C

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• C(100/25)C'
• C' mg/ml
• C mg/ml
• C0 mg/ml
• ?W(C0-C)V10-3 g

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Calculate the specific surface of silica gel.
NA6.021023 A cm2
M 373.9 W g
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Questions

• 1.Why should the adsorbed solution be diluted
  before determination?
• Whats the applied condition of Eq.1?

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Attentions

• Solution should be confected accurately.

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Outline for controlling 722-Spectrophotometer.

• 1. Regulate the sensibility at the lowest value,
  when it is of the smallest amplificatory times.
• 2.   Electrify and warm-up for 20 min, set the
  switch at T.

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• 3.Open the sample compartment, adjust 0Tto the
  value of 0.000.
• 4. Adjust the wave at appointed value.
• 5. Cover the door, adjust 100T to the value
  of 1.000, if not, improve its sensibility.

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• 6.     Determination of the absorbance.
• Set the switch at A and measure the
  absorbance according to the steps above.
• 7. Finally, clean the instruments, cut down the
  electricity and cover the dustproof.