ABSTRACT
THE IMPORTANCE OF FINE PARTICLES IN PHARMACY Although fine particles can be produced directly by controlled precipitation, crystallization, or drying a fine spray of solution, in many cases the material is powdered in some kind of mill. From our point of view, the most important result of this operation is the increase in the surface area of a given weight of the powder and its influence on diffusional processes. A cube of side 0.01 m has a surface area of 6 104 m2. If, by some ideal size reduction process, this cube was divided into cubes of side 0.001 m, we should have a thousand particles each with a surface area of 6 106 m2 and a total surface area of 6 103 m2. A tenfold increase in surface area has been given by a tenfold decrease in particle size. Generalizing, we may say that the surface area is inversely proportional to the particle size assuming that the shape of the particles remains the same.
