Question

Why Ph.Ph indicator is not used instead of methyl red indicator in the standardization of HCl solution by borax?

Answer 1

see below

Explanation:

A pH indicator can be useful if its range of colour change is around the equivalent point of the titration.
At the equivalent point of titration of borace with HCl you have tetraboric acid with an acid pH (about 4-5, it depends from concentation), so you must use Methyl red (it changes its colour at pH 5) and not Ph that change its colour about pH 8,5