Surface area and pore structure of talc‐magnesite

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Abstract
The effect of thermal treatment on talc‐magnesite in the presence of air in the temperature range 500–1000°, was studied by nitrogen adsorption and followed by t.g.a., d.t.a. and X‐ray analysis. From the nitrogen adsorption isotherms, the specific surface area as well as pore‐size distribution was estimated. The surface area increased with temperature, to reach a maximum at 600°. On immersion of the calcination products in water, magnesium hydroxide was formed. Decomposition of the hydration products in air at 450° resulted in solids of relatively higher surface areas, whereas decomposition in vacuo at the same temperature produced more active solids. Surface area of the products produced in vacuo decreased only slightly with the primary decomposition temperature, and they are characterised by sharp pore‐size distribution curves. Surface areas of the products produced in air were dependent on the primary calcination temperature, although they showed pore‐size spectra similar to those of the other products. Products obtained by direct decomposition in air showed wider pore spectra that shifted towards higher pore radii with rise of temperature.