Particle Packing, Mass, and Size Distribution

If powders are used for the sample material, the packing of the particles will have an effect on the rate of reactions involving gases. Tighter packing inhibits free diffusion of gaseous species in and out of the reaction zones. Hence, the decomposition 

For post-type DTA s in which thermocouple junctions measure the temperature of the container of the sample (e.g. platinum or poly crystalline alumina crucibles), good mechanical contact between the sample and the bottom of the crucible will improve instrument sensitivity to transformations. Surface contact may be optimized by using samples shaped to match the crucible, or finely crushed granules, as opposed to more spherical or odd-shaped chunks. Optimum mechanical contact minimizes the lag time between when a reaction occurs and when heat propagates to/from the point of temperature measurement, and the reaction is recorded. 

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