Tg Thermogravimetry Research Paper

Name: Junior Paul ID Number: 158599

CHE 609 THERMAL AND ELECTRO-ANALYTICAL METHODS

Assignment 1: Solution

TG: Thermogravimetry DTG: Derivative Thermogravimetry

1. Inaccuracies in a TG thermogram are due to the following sources of error which can be reduced as described below:

Sample-container air buoyancy: It refers to the apparent weight gain when an empty sample container is heated. It results in decreased air buoyancy, increased convection and heat effect on balance mechanism [1].The density of the gas phase and hence the buoyancy exerted on the sample decreases with an increase in temperature. It is low at a high temperature. These pressure fluctuations result in a deviation in the mass-change curve. It can be eliminated

The magnitude of error (temperature difference) also depends on the nature of the reaction whether reaction is endothermic or exothermic, the heating rate sample thermal conductivity, and geometry of sample holder [2]. It can be reduced by using a small amount of sample to minimise diffusion controlled weight loss and promote better homogeneity of temperature than can be obtained with larger samples [4], lowering heating rate, correcting for sample container temperature (by taking a difference between crucible and furnace thermocouple)[6] and proper positioning of thermocouple that is to say placing thermocouple very close to sample but not in contact with it in a zone where temperature would be equal to that of an empty sample pan

Accordingly, DTG curves can give exact quantitative analyses.

DTG curves are highly reproducible.

DTG curves indicate exactly the temperatures of the beginning, maximum rate and end of change.

DTG curves give fair results in investigation of organic compounds that melt on heating and cannot be analysed by DTA.

References

[1] Newkirk, A.E;Anal. Chem., 32, 1558 (1960).

[2] Wendlandt, Wesley.M. Thermal Methods of Analysis. 2nd edition.New York: John Wiley and Sons, Vol.19, 1974, pp.29-44.

[3] Mehran Heydari, Moshfiqur Rahman and Rajender Gupta. Kinetic Study and Thermal Decomposition Behavior of Lignite Coal. In International Journal of Chemical Engineering Vol.2015(2015). http://dx.doi.org/10.1155/2015/481739.

[4] Friedman, Henry. L. Anal. Chem; 37, 768 (1965).

[5] Wendlandt, W.W; and E. L. Simmons, Thermochim. Acta, 3, 171 (1972).

[6] Dmitriev, A.L. Thermogravimetry and the Negative Temperature dependence of gravity, in Applied Physics Research; Vol.7, No.6; 2015.

[7] Erdey, L; F. Paulik, and J. Paulik, Nature,