The pore structure of an alumina membrane was studied by adsorption in
conjunction with small-angle neutron scattering (SANS). The effect of
an incomplete contrast matching was investigated and simple formulae
allowing the calculation of the amount of water adsorbed and the film
areas, at various relative pressures, were derived for the ternary sys
tem. In the vicinity of the contrast matching point, however, incomple
te contrast matching does not introduce a substantial complication to
data analysis. The adsorption isotherm was reconstructed from the SANS
data and agrees well with the experimental adsorption isotherm. For t
he alumina membrane, a coordination number of approximate to 10 was es
timated from the SANS determined areas.