Quantasorb surface area analyzer was used for mea
suring the surface area of the fillers. The weighed sample was taken in the cell holder and taken into the sample station. When a stable base line had been established, the signal meter was set to zero and the cells immersed in the liquid nitrogen. As the peak of the adsorption signal was app. 50-60% on the signal meter, it was set to zero. The integrator was reset and the sample cell immersed in a beaker filled with water until the sample rotometer ball returned to within 1cm of its starting position when the sample had been returned to zero, the integrator count was recorded. A sample of calibrating gas was injected using a gas tight syringe, the calibration volume and integrators reading were recorded. This experiment was repeated two more times by changing the volume of nitrogen.