The crystallite dimensions of a new solvay type catalyst for propylene polymerization were determined from the data of breadth of X-ray diffraction lines at half peak intensity. The crystallites have the size of about 100 A and they are smaller then those prepared by other methods. Their catalytic activity increases linearly with decreasing crystallite size.Surface area and pore structure of the catalyst were determined by elution chro-matographic method on model ST-03 analyzer. Our results showed that such catalyst possess high specific surface area and large pore volume and has both large and fine pores. Therefore

active centres can be fully available.