When the mild alkali solution is added to the mild acid solution drop by drop, the pH value of the solution gradually increases. In this case, even if it comes close to the quenching point, no sudden change in the pH value of the solution can be caused. This is because the pH value of the solution increases very slowly from start to finish. Therefore, no specific indicator is effective in this case. However, in such mitigation reactions a mixture of instructional phenethylene and methyl red is used. So it can be said that there is no suitable indicator of mild acids and mild alkalis.