Re: How do you calculate the Buffering Capacity of a substance?

Buffering capacity(beta) of a buffer solution, is defined as:
Beta = delta b/delta pH(or ®Cdelta b/ delta pH)
delta b (or delta a) stand for the moles of strong base (or acid) needed to 
be
added into a liter of buffer to increase (or decrease) a little pH value 
unit
of the buffer. For the HB-B buffer system, the buffering capacity is the 
total
buffering capacities of H+(betaH=2.30[H+]), OH-(betaOH=2.30[OH-]),
HB(betaHB=2.30C*deltaHB*deltaB). Note: C is the total concentration of the
buffer, deltaHB, deltaB here are the distribution coefficients of HB and B) 
the
1:1 HB-B concentration condition, the buffer capacity of the solution is
maximal, which is 0.575C( C is the total concentration of the buffer).

However, under your circumstances in which Hydrochloric Acid is a strong 
acid,
the buffer capacity is only provided by H+. So the calculation of its 
buffering
capacity can be simplified as:
Beta = 2.30[H+].
( since pH = -log[H+] = -ln[H+]/2.30, so delta pH = -delta [H+]/2.30[H+] ,
then  -delta [H+]/ delta pH = 2.30[H+].

Reference: Analytical Chemistry, Wuhan University ed., Higher Education
Press:Beijing.