Correct Answer: is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle.
8. Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in pebble mill are made of
Correct Answer: Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products.