High pressure sorption apparatus
The main part of this apparatus is the thick-walled glass sorption cell certificated up to pressure 20 bar. This cell is equipped with the McBain’s spiral quartz balance with the spherical reference point. Measured sample is attached to a spiral by a tiny kanthal wire or was placed in an aluminum basket (brittle pieces of membranes). Measured spiral prolongation due to mass change of sample is proportional to the determined spiral buoyancy constant. A mass change of membrane due to gas sorption is observed by CCD camera (Sony) targeted to spherical reference point and is recorded by PC – selected scanning period was set in time interval 0.4 - 60 seconds depends on the appropriate sorption kinetic velocity. The apparatus is located in Plexiglas box insulated with 1 cm thick poly(styrene) plates and is thermostated by heating (Bravo B 4273) and cooling machine (Julabo F250) to temperature (25.0 ± 0.2) °C. The temperature is controlled using precise mercury thermometer. Air circulation inside the whole box is arranged by air fan located inside heating unit. Before each experiment, the sorption cell is evacuated with the oil pump (Trivac D4B, Oerlikon Leybold) to pressures lower than 0.01 Pa. The pump is equipped with an oil filter eliminating contamination of cell by leaking oil mist. The apparatus is stabilized using the active vibration isolation table (Thor Labs).