A New Method of Differential
Thermal Analysis
L. HEMPHILL, Associate Professor
A. D. RAY, Associate Professor
E. L. SIMMONS, Graduate Student
Civil Engineering Department
University of Missouri
Columbia, Missouri
INTRODUCTION
The purpose of this study was to devise a specific method of differential
thermal analysis (DTA) for organic waste materials and to determine the nature of
exothermic DTA response.
Development of an analytical method for organic waste materials requires
comprehensive evaluation of the basic analytical theory, development of a practical
application method, and determination of sensitivity, resolution, and precision of the
method. DTA is a well-established analytical method which is used extensively in the
earth sciences. Thus, the basic theory, design, and technology appropriate to the
DTA analytical method has been developed (1). Results of a previous study (2),
based on direct application of clay mineralogy DTA practices, showed that DTA of
organic waste materials: 1) produced characteristic exothermic and endothermic
patterns; 2) exothermic peak area was directly proportional to organic sample mass;
3) the shape or pattern as well as area of the exothermic peaks changed during the
course of biological oxidation, and; 4) the results of DTA, a thermogram, contains
qualitative and quantitative information.
This latter finding was considered most promising; it is rare that qualitative and
quantitative information relative to organic materials can be extracted in one analysis.
Study of the previous work showed that although the potential of DTA was
promising, the direct determination of the analytical sensitivity, resolution and precision of the method required further work. This presentation describes development of a method specifically for DTA of organic materials.
In the past, DTA has been used chiefly to study the structural changes and rearrangements which occur in clay minerals and similar materials. Many of these
changes are low energy rearrangements which are related to changes in molecular
orientation or sorption of water. The evaluation of the type of reaction or series of
reactions related to a DTA thermogram is usually provided by systematic analysis of
endothermic peak patterns. Preliminary study and observation has shown that organic DTA produce exothermic patterns almost exclusively. Moreover, the conventional or clay mineralogy technique for sample preparation was determined to be
incompatible with organic DTA requirements. Many compacted organic samples explode when subjected to a high temperature environment. Thus, the basic need for
development of a specific method for organic DTA was initiated.
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