# Plate Theory and Extensions - The Peak Capacity of a Chromatographic Column > Page 93

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Thus, the base width of the (r)th peak will be, .

Consider the point where the last two peaks contact. At this point the retention volume of the last peak, minus half the peak width at the base, will equal the retention volume of the penultimate peak, plus half its peak width at the base.

Consequently,

and,

Thus, (75)

Therefore, for
the peak with a *base* width (w_{(r -1)}) of peak (r* *-1),