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Dnyanasadhana College, Thane . hhh

Dnyanasadhana College, Thane . hhh Department of Chemistry T.Y.B.Sc. Analytical Chemistry Paper-IV Sem-VI DIFFERENTIAL THERMAL analysis Dr.Bhagure G.R. Contents. 4.1.3 Differential Thermal Analysis (DTA): Principle, Instrumentation –balance, Thermocouple

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Dnyanasadhana College, Thane . hhh

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  1. Dnyanasadhana College, Thane. • hhh Department of ChemistryT.Y.B.Sc. Analytical ChemistryPaper-IV Sem-VI DIFFERENTIAL THERMAL analysis Dr.Bhagure G.R.

  2. Contents • 4.1.3 Differential Thermal Analysis (DTA): Principle, • Instrumentation –balance, • Thermocouple • Reference material used in TA (MgO,Al2O3,SiC), • DTA curve • Applications : DTA of CaC2O4.H2O and CuSO4.5H2O, Difference between TGA and DTA.

  3. Principle of DTA When a graph of ∆T Vs. temperature is plotted, the maxima and / or minima due to exothermic and/ or endothermic processes. Maxima and minima are called as peaks. Maxima = exothermic process in which heat is evolved from the sample causing temperature to increase. Minima = endothermic process in which heat is absorbed by the sample causing temperature to decrease.

  4. Peak area (A) is corrected to the mass of the analyte (m) as A = K G m ∆ H = K’ m ∆ H G = calibration factor related to sample geometry K = constant related to thermal conductivity of sample K’ = constant related to heating rate, particle size, placement of sample etc. The mass of a particular analyte can be determined if K’ and ∆ H can be known by calibration.

  5. DIFFERENTIAL THERMAL ANALYSER

  6. SCHEMATIC DIAGRAM OF DTA INSTRUMENT ---------------------------------------------------------------

  7. Reference material used in DTA (MgO,Al2O3,SiC

  8. DTA curve of CaC2O4.H2O in the presence of O2. Heating rate = 80C/min

  9. Calcium oxalate monohydrates gives two endotherms

  10. Calcium oxalate monohydrates gives one exotherms

  11. DTA curve of CuSO4.5H2O in the presence of O2. Heating rate = 80C/min • ∆T 100 200 250 300 

  12. DTA curve of CuSO4.5H2O gives three endotherms

  13. DIFFERENCE BETWEEN TGA & DTA TGA DTA Measure the temperature difference between sample and reference with increase in temperature. Plots a graph of ∆T Vs. T maxima and minima gives information about exothermic and endothermic processes associated with sample • Change in mass of sample with increase in temperature • Plots a graph of change in mass Vs. T • Change in mass gives information about • Change in sample composition • Change in thermal stability • Change in kinetic parameter

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