Buffer index is

Explanation

Buffer index, `Beta`, as a quantitative measure of the buffer capacity. It is defined as the number of gram equivalents of acid or base added to 1 litre of the buffer solution to change its pH by unity.
`Beta=(dB)/(d(pH))`
Here,
`dB=` number of gram equivalents of acid/base added to one litre of buffer solution
`d(pH)=` The change in the pH after the addition of acid/base.