Estimation of Useful Shelf Life

By contrast, DSC provides a fast and economical alternative. However, because of the marginal sensitivities of some commercial instruments, high temperatures and long extrapolations sometimes become necessary. The method is also non-specific, in the sense that energy changes, rather than chemical changes, are measured. 

With the aid of these experimental quantities, the following parameters can be calculated  

For a general reaction, such as aA + bB - cC, the heat flow can be expressed as 

By plotting power dqjdt) against heat flow (q), the constants AH, k, m, n, A, B can be determined by a process of iteration. 

For processes with AH = 40 kJ moP microcalorimeters can detect reaction rates corresponding to 6 pmol month Alternatively, for first-order rate constants of 10 ° s half-lives of 200 years can be conveniently measured (equivalent to reaction rates of 0.3% per year). For examples of various aspects of isothermal microcalorimetry, see Refs. 146-148. 

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