Dear all. I am studying the graphene as reinforcement phase of electrical conductive polymer composite. But I have some problems about measuring electrical conductivity of graphite powders. I have read some articles which related to electrical conductivity of graphite and reduced graphite oxide. In these, they use GEM equation (more exactly is derivative GEM equation), as following: In this formula, two parameters [tex]\Phi[/tex] and [tex]\Phi[/tex]c relate to the apparent powder density before compression. I don't know how to measure the apparent powder density ??? Can you help me to resolve it ? In summary, I want to measure electrical conductivity of powders, and I just know one method above. If anyone has studied it, please support me some other methods. Thanks in advance.