Methods When the Infinity Reading End Point is Unknown

5 METHODS WHEN THE INFINITY READING ( END POINT ) IS UNKNOWN 

Kinetic data may be collected in which the final instrument reading is unreliable or unavailable. Perhaps excessive time would be needed, or a slow secondary reaction sets in, or the instrument baseline slowly drifts. Nowadays, with readily available nonlinear least-squares programs, one may simply treat as a floated variable, along with k. 

Kinetic data for the reaction between PuOi- and Fe2+, given in Table 2-4, are fitted to the integrated rate law for mixed second-order kinetics. The solid curve represents the least-squares fit to Eq. (2-34). left and (2-35). right. 

There are, however, other options for treating data from both first- and second-order kinetics. Collectively, they are known as time lag methods. These methods are primarily of historical interest, although the mathematical rearrangements provide insights into the nature of the functions involved. 

Consider a first-order reaction, in which early points are paired with later ones. The time interval between members of each pair is symbolized as r, and it is the same throughout. The values of Y, and F,+T are 

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