Oil extrusion and constant pressure head methods to determine surface area of granular carbon powders

Abstract

Surface area of granular powders such as carbon powders used in the manufacture of cinema arc carbon rods, brushes etc. was determined by the method of oil extrusion. The granular powder thoroughly dispersed in anthracene oil of density d was poured into a Buchner funnel to a few millimeters depth. An increasing suction pressure was applied till it reached the maximum possible value. Critical pressure p c at which rapid displacement of oil took place and v the volume of oil retained after complete extrusion of oil at pressure p c were observed and r the capillary radius corresponding to p c was determined. Then applying the above values of v and r in an empirical equation similar to Wicke's equation, S the surface area was determined. The results were tested using Blaine's method and constant pressure head apparatus designed by the authors.