授課教師: Professor 吳逸謨 教授    Warning: Copyrighted by textbook publisher. 
                                     Do not use outside class.  
          Principles of Instrumental 
                         Analysis 
                        Section Six 
       Miscellaneous Methods   p. 893 
                        Chapter 31 
                  Thermal Methods 
            Contents: TGA, DTA, DSC 
                                  
                            Time: 3 hrs (1 week)             11  
               Miscellaneous Methods 
 Chap. 31  Thermal Methods     DSC, DTA, TGA 
  
 The following Chapters are not covered: 
 • Chap. 32 Radiochemical 
 • Chap. 33 Automated analyses 
 • Chap. 34 Particles size determination 
 Laboratory items – 下學期實驗課 
  
 DSC – Differential scanning calorimeter 
 [Note: DTA is similar to DSC.  DTA is less often used now.] 
  
 TGA (2008購) – Thermogravimetric analyzer 
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     Chapter 31   Thermal Analysis                            p.894 
 Thermal Analysis – Definition 
      Techniques in which a physical (thermal) property of a 
    substance is measured as a function of temperature while 
    the substance is subjected to a controlled temperature 
    variation.    
  
 More than a dozen of such thermal techniques are used.  
    But only three techniques are covered in this chapter: 
      1. Thermogravimetry analysis (TGA) 
      2. Differential thermal analysis (DTA) 
      3. Differential scanning calorimetry (DSC) 
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  TGA                                                                                                  p. 894 
       The mass of a sample in a controlled atmosphere is recorded 
       continuously as a function of temperature (or time) as the temperature 
       of the sample is increased. 
   
  TGA thermogram: 
       - A plot of mass percent as a function of time or temperature. 
       [TGA measures the change in weight of a sample as it is heated, cooled or 
       held at constant (isothermal) temperature.] 
   
  Instrumentation of TGA includes the following: 
  (1) A sensitive analytical balance  
       Range : up to 100 mg. 
       Sample holder is in furnace.  However, the rest of the balance must be thermally 
       isolated from the furnace.   
  (2) furnace 
            Temperature range: up to 1500oC. 
  (3) purge gas system 
            For prevention of oxidation: N2, Ar, He, etc. 
            For oxidation: O2 or air.  
  (4) Temperature control and a computer for data acquisition /display.                                                                44