Switch to a 100 uL pipette, add 100 uL at a time. Near the equivalence point, when the colour starts to change to pink more markedly but after mixing the orange colour returns, it is necessary to add HCl drop by drop. The first drop that causes a permanent colour change to pink determines the equivalence point. Stop adding HCl. Cap the tube, hold tube horizontally, gently invert the tube to wash residue at the inner side of the cap down to the solution. The color may change back to orange, add more drops of HCl until the color turns to permanent pink again (See the color of the left tube).