I have obtained negative BET-N2 values for Boehmite, calcite and wollastonite, and unusually low values for Gibbsite (~1 m2 g-1). All samples were pretreated by heating them up at 105ºC for 24 h under vacuum conditions.

We ruled out malfunctioning of the equipment, as hematite, Goethite and ferrihydrite were measured under same conditions yielding values that are comparable to reported values in the literature.

Any thoughts and advices on this will be very appreciated.

 - Dalton