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  Section: Practical Skills in Chemistry » Instrumental techniques
 
 
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Thermogravimetry

 
     
 
Content
Instrumental techniques
  Basic spectroscopy
    Introduction to spectroscopy
    UV Ivisible spectrophotometry
    Fluorescence
    Fluorescence spectrophotometry
    Phosphorescence and luminescence
    Atomic spectroscopy
  Atomic spectroscopy
    Atomic Absorption Spectroscopy
    Atomic Emission Spectroscopy
    Inductively coupled plasma
    Decomposition techniques for solid inorganic samples
  Infrared spectroscopy
  Nuclear magnetic resonance spectrometry
    1H-NMR spectra
    13C-NMR spectra
  Mass spectrometry
    Interfacing mass spectrometry
  Chromatography ~ introduction
    The chromatogram
    Resolution
    Detectors
  Gas and liquid chromatography
    Gas chromatography
    Liquid chromatography
    High-performance liquid chromatography
    Interpreting chromatograms
    Optimizing chromatographic separations
    Quantitative analysis
  Electrophoresis
    The supporting medium
    Capillary electrophoresis
    Capillary zone electrophoresis (CZE)
    Micellar electrokinetic chromatography (MEKC)
  Electroanalytical techniques
    Potentiometry and ion-selective electrodes
    Voltammetric methods
    Oxygen electrodes
    Coulometric methods
    Cyclic voltammetry
  Radioactive isotopes and their uses
    Radioactive decay
    Measuring radioactivity
    Chemical applications for radioactive isotopes
    Working practices when using radioactive isotopes
  Thermal analysis
    Thermogravimetry
    Applications

The apparatus required for TG analysis is shown in Fig. 36.1. TG is normally carried out on solid samples. Example operating conditions are as follows:

  Sample:
Crucible:
Rate:
Atmosphere:
Mass:
calcium oxalate monohydrate
platinum pan
10 K min−1
nitrogen, 20 mL min−1
10.5 mg

The result can be expressed as either a TG curve, a plot of changing weight with respect to temperature or time, or a derivative of the curve, i.e. DTG, where the first derivative of the TG curve is plotted with respect to temperature or time. As well as providing information on the thermal decomposition of inorganic compounds, additional information can be deduced, e.g. sample purity and Mr

The oxalate hydrates of the alkaline earth metals, e.g. calcium, strontium and barium, are all insoluble. If a calcium salt made acidic with ethanoic acid is treated with sodium oxalate solution, a white precipitate of calcium oxalate monohydrate is formed quantitatively. After washing the precipitate with ethanol it can be analysed. A typical TG curve, for calcium oxalate monohydrate, CaC2O4.H2O, is shown in Fig. 36.2. Box 36.1 shows how to interpret a thermal analysis trace for calcium oxalate monohydrate.

Schematic diagram of a system for
Fig. 36.1 Schematic diagram of a system for thermogravimetry.
 
A typical thermal analysis trace for
Fig. 36.2 A typical thermal analysis trace for
CaC2O4.H2O.


 
     
 
 
     



     
 
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