Differential Thermal Analysis Introduction, Reference and Standard material, Instrumentation in that Furnace, Sample holder, Furnace temperature controller, DC amplifier and Recorder. Principle, Factors Affecting, Working, Physical and chemical reactions (Endotherm and Exotherm), Advantages and Disadvantages, Applications

1. D
DIFFERENTIAL THERMAL ANALYSIS
Presented by - Mayuri M. More
Department - QAT
Modern College of Pharmacy (For
ladies),Moshi,pune

2. Content -
 Introduction
 Principle
 Instrumentation
 Factors Affecting
 Working
 Advantages
 Disadvantages

3. INTRODUCTION -
 When material is heated it's structural and chemical
coposition can undergo changes such as fusion,
melting, crystallization,oxidation,
decomposition,transition and expansion.
 Using Thermal Analysis such changes can be
monitored in every atmosphere of interest.

4. Principle -
"Differential Thermal Analysis (DTA) is a
technique in which the difference in temperature
between a substance and a reference material is
measured as a function of temperature."

5. Instrumentation -
 A few milligram of the sample (S) and an inert reference
material/substance (R) are contained in small aluminum dishes
located above sample and reference thermocouple in an
electrically heated furnace.
 The DTA apparatus consists of the following components -
1. Furnace : Which is used for heating the sample.
2. Sample holder : which is used to contain the sample as well as
the reference material.
3. Furnace temperature controller : To increase the temperature
of the furnace at a steady state.

6. 4. Furnace atmospheric control system : To maintain sutaible ,
atmosphere in the furnace and sample holder.
5. DC Amplifier : Generally Low DC Amplifier is used.
6. Recorder : This is to record the DTA Curve.

7. Factors Affecting the DTA Curve -
 Size and shape of the sample and furnace holder.
 Material from which sample holder is made and its
corrosive attack.
 Amount of sample.
 Characteristics of sample.

8. Working Principle Of DTA -
 The temperature difference between the sample and (Ts) and that
of the reference (Tr) is measured by the differential
thermocouple, and the output signal (Ts -Tr) .
 If , there is an exothermic reaction in the sample the sample
temperature increases faster than the reference temperature(+ve).
 If , there is an endothermic reaction in the sample temperature
increase slower than the reference temperature (-ve).

9. Fig - Endothermic and Exothermic Curve

10. Advantages -
1. Instrument can be used at very high temperatures.
2. Instrument are highly sensitive.
3. Characteristics transition or reaction temperature can
be accurately determined.

11. Disadvantages -
1. Uncertainty of heat of fusion, transition , or reaction
estimation is 20 -50 %.

12. Applications -
1. DTA is used for qualitative and quantitative analysis.
2. DTA is widely used tool for studying and characterizing
polymers. (Physical and chemical changes of polymers.).
3. DTA is also widely used in ceramics and metals industry.
4. DTA is used to study decomposition temperature, phase
transition, melting and crystallization points and thermal
stability.

13. 5. DTA method also provide a simple and
accurate way of determining the melting, boiling
and decomposition points of organic
compounds.

14. Reference -
1. Douglass A. Skoog, F. James Holler, Principle of
Instrumental Analysis , 5th edition New York 2001.
2. Mr. Shaise Jacob Faculty Department of Pharmaceutical
Analysis Nirmala College of Pharmacy Muvattupuzha,
Kerala.

15. Thank You