Determination of the Specific Surface—Solution Adsorption 退出

1. 比表面测定 ——溶液吸附法 Determination of the Specific Surface—Solution Adsorption 退出

2. Contents • Purposes and Demands • Principle • Apparatus and Reagent • Procedure • Data Records and Processing • Questions • Attentions 退出

3. · 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.

4. 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.

5. 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.

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

7. 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 admolecule’s number is multiplied by the area of an adsorbed molecule.

8. The total area of the solid is Where S, A, M , NA, W, ΔW, are respectively, the specific surface with( cm2/g), the cross-sectional area of methylthionine-chloride molecule( 81.3×10-16cm2),

9. 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.

10. 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.

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

12. 实验原理 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.

13. 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（500×10-3mg/ml） • micro-silica gel

14. Procedure • 1.Determination of the specific surface ⑴ Prepare the Methylthionine-chloride solution of 50×10-3mg/ml for reservoir liquor. Pipette the 10ml liquid of 50×10-3mg/ml to a 100ml volumetric flask and make up this solution.

15. ⑵ 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.

16. 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.

17. Methylthionine-chloride （500×10-3mg/ml） 1.00 2.00 3.00 4.00 5.00 6.00 Concentration （（×10-3mg/ml） 5 10 15 20 25 30 Absorbance 实验步骤

18. 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

19. C＝（100/25）C′ C′ = mg/ml C = mg/ml C0 = mg/ml ΔW＝（C0－C）×V×10-3＝g

20. Calculate the specific surface of silica gel. NA：6.02×1023 A： cm2 M： 373.9 W： g

21. Questions • 1.Why should the adsorbed solution be diluted before determination? • What’s the applied condition of Eq.1?

22. Attentions • Solution should be confected accurately.

23. 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’.

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

25. 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.