The dissociation constant of bromocresol purple indicator is 3.981 × 10-7 at 0° C. The indicator when added to a buffer solution gave a colour matched with 50% basic colour and rest matched with acidic colour. The pH of buffer is: [log 3.98 = 0.5999]
1
7.40
2
3.25
3
6.40
4
5.40