The paper "Optimal use of mixed catalysts for two successive chemical reactions" by Jackson was first presenting an analytical solution for the plug flow reactor catalyst blend problem. However, the exact optimal value of the problem was not given, which has caused confusion and inaccuracies in the subsequent literatures. As a supplement and correction, this study gives the optimal solutions and optimal objective values analytically for the cases when the reactor length equals 1 and 12. These results are also verified numerically using the time-scaling method.