[T - $]-”’}
APPENDIX B
{ nD(t - T ) )-,I2
Curve D E in Figure 2 is an approximation to C ( x , T ) which is the more valid the smaller x, being exact for x = 0. Curve EF is based upon a completely different approximation and becomes exact as the ratio T / T approaches zero. The two curves coincide at x = 0 because EF has been “fitted” at this point. However, no such fit has caused the coincidence of the curves at non-zero x values, yet the figure shows that the two curves are virtually identical out to about x = 7 d D 7 The agreement of these two quite independent approximations for o < x < 7 4 0 7 and T / T = 0.01 strongly suggests that both correspond very closely to the true C ( x , T ) under these conditions. Recall that the depletion caused by the first pulse did not extend beyond about 5 d & ( F i g u r e 2). One is justified therefore, in expecting that only that section of the concentration profile lying well within the range 0
