At present there is a growing interest to porous carbon due to its large field of application. Porous activated carbons with their large surface area and microporosity are one of the most prospective systems in hydrogen storage for fuel cell application. The value of such systems is their hydrogen capacity at a certain conditions. For hydrogen mass uptake evaluation (which is the most crucial characteristic for gas storage technology) we need a precise value of the density, determination of which becomes tricky for highly porous materials. SANS provides direct and accurate measurement. The aim of the experiment is to use Contrast Match method for density determination. Applying for match composition at different pressure steps p/p0 we can analyse the nature of the porosity in studied sample. We would also like to determine Q and time dependence of H/D exchange process