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Journal of Thermal Analysis and Calorimetry

, Volume 121, Issue 1, pp 187–194 | Cite as

The effect of volatiles on the measurement of the reaction heat by differential scanning calorimetry

  • Eduard García
  • Daniel Sánchez-Rodríguez
  • Joan Pere López-Olmedo
  • Jordi Farjas
  • Pere RouraEmail author
Article

Abstract

When gases evolve during a chemical reaction, a fraction of the reaction heat is lost with them. We have analyzed, both theoretically and experimentally, the deviations that this effect can produce on the determination of the reaction heat by differential scanning calorimetry (DSC). It is shown that, even in the absence of gas overheating, deviations related to variations in the sample heat capacity can be substantial in experiments involving very intense DSC peaks. However, experiments performed on thermal decomposition of metal organic salts and on evaporation of liquids have shown that deviations usually arise from gas overheating.

Keywords

DSC Reaction heat Boiling Decomposition Overheating Volatiles 

List of symbols

α

Transformed fraction

β

Heating rate of the reference temperature

C

Heat capacity of the sample placed inside the pan

CA, CB

Heat capacity of the solid sample at the beginning and at the end of the reaction

CG

Heat capacity of the evolved gas

cpS, cpL, cpG

Specific heat capacity (per unit mass) at constant pressure of solid, liquid and gas

CREF

Pan heat capacity

DSCP

DSC value after baseline subtraction

ΔH

Enthalpy of reaction

ΔTG

Gas overheating above T S

ΔQC, ΔQG, ΔQP

Corrections to the measured heat due to gas evolution (see main text)

LBOIL

Latent heat of boiling

LEV

Latent heat of evaporation

m

Mass of the sample remaining inside the pan

Q

DSC peak area (after baseline subtraction)

\( \dot{q}_{{}} \)

Heat power exchanged due to a chemical reaction \( \left( {\Delta H = - \int {\dot{q}} \,{\text{d}}t} \right) \)

\( \dot{Q}_{\text{REF}} \)

Heat power flowing through the “sample” side of the DSC sensor

\( \dot{Q}_{\text{S}} \)

Idem through the “reference” side

R

Thermal resistance of the DSC sensor

TBOIL

Boiling point

TREF

Temperature at the “reference” side of the DSC sensor

TS

Temperature at the “sample” side of the DSC sensor

τSIGNAL

Time constant characteristic of the DSC signal

Notes

Acknowledgements

This work was partially funded by the Spanish Programa Nacional de Materiales through projects MAT2011-28874-C02-02 and by the Generalitat de Catalunya contract No. 2009SGR-185. The authors thank the University of Girona for the PhD fellowship granted to Daniel Sánchez-Rodríguez and for the use of the thermal analysis facilities (Serveis Tècnics de Recerca).

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2015

Authors and Affiliations

  • Eduard García
    • 1
    • 3
  • Daniel Sánchez-Rodríguez
    • 1
  • Joan Pere López-Olmedo
    • 2
  • Jordi Farjas
    • 1
  • Pere Roura
    • 1
    Email author
  1. 1.GRMT, Department of PhysicsUniversity of GironaGironaSpain
  2. 2.UAT, Serveis Generals de RecercaUniversity of GironaGironaSpain
  3. 3.Industrias Cerámicas BrancósLa BisbalSpain

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