1) Methyl Orange: Methyl orange is an indicator that changes colour from red to orange in acidic solutions. When hydrochloric acid is added to a solution containing methyl orange, it turns the solution orange.
2) Congo Red: Congo red is another indicator that changes colour from blue to red in acidic solutions. When hydrochloric acid is added to a solution containing Congo red, it turns the solution red.
Both methyl orange and Congo red turn red in the presence of hydrochloric acid, making them useful indicators for detecting the presence of this acid.
