Precise evaluation of surface area with indirectly calculated dead space

Abstract

The determination of surface ar ea f rom ni trogen a dsorp tion data ob tain ed at low temper at Ul'e by vol umelri c m ethods is s ubj ect to several error. One error that becomes especially seri ous when t he surface area is small is associated wi t h t he cali bration of t he dead space with heli um. This er ror is large because the vo lume of adsorbed gas is calc ul ated as a sm all diffe rence between two comparatively large quantiti es. A statistical method of s uccessive a pproximations has been developed for calculating t he dead space. The latte r is obtained as t hat q uantity necessary t o y ield t he best agree-m ent with t he known isotherm equation. T h is pro ced ure fi xes t he va lue of V m (directly proportiona l to t he surface area). The p roced ure a lso provides fin es ti mate of t he expe rim ental error a ssoc iated wi th t he overall determination.