DTA

       DTA-differential thermal analysis.

      •In  both the test sample and an inert reference material (usually α-alumina) undergo            controlled heating or cooling program which is usually linear with respect to time.

        •There is a zero temperature difference between sample and reference material when the formal dose not undergo any chemical or physical change.

       •If, however any reaction takes place, then a temperature difference ∆T will occurs between the sample and the reference material.

•Hence in endothermic change 

  e.g. when the sample melts or is dehydrated, thesample temperature is lower than that of the reference material.

•This condition is only transitory because on completion of the reaction the sample will again show zero temperature difference compared with the reference.  

      •In DTA a plot is made of ∆T against temperature or time, if the heating or cooling program is linear with respect to time an idealized DTA curve is shown in figure:-