Abstract In Avogadro constant measurement experiment by single molecule membrane, the diffusion agent benzene has weaknesses such as high toxicity and big experiment error. Through analyzing literatures, it was found that the physical properties of cyclohexane, n-hexane accorded with the requirement of diffusion in this experiment, and their toxicity was lower than that of benzene. So cyclohexane, n-hexane and benzene were chosen to do contrast experiment. The experimental results showed that using cyclohexane as diffusion agent NA was the closest to the theoretical value. Therefore, this paper suggested using cyclohexane as diffusion agent in Avogadro constant measurement by single molecule membrane.
