AbstractIn most rate process problems, the original experimental data must be differentiated to obtain the derivatives, which are the information actually sought. For first derivatives all the commonly used methods give about the same result. However, the common methods of calculating derivatives can give very different second derivatives for the same set of starting data. Thus, in problems in which the desired result is a second derivative, the answer obtained is a strong function of the method used to calculate second derivatives. This is illustrated by several examples.