The method of extraction can separate a substance from one or more others by using a solvent because there have variations in the solubilities of different compounds in different solvents. The natural
dyes extracted from Chinese gall havewater-soluble ability and water was used as extraction solvent when the Chinese gallnuts were extracted. According to diffusion phenomena and thermodynamic
equilibrium, the extraction of Chinese gall was a mass transfer process between solid and liquid phases. After the solid particles of Chinese gall were desorbed, dissolved and diffused the
colorants were transported from Chinese gall to water as a result of random molecular motions. Batch solvent extraction is never total and there is a partition factor between solid and liquid phases when the equilibrium is reached. The partition factor is expressed in terms of the final fractional uptake of the solid particles by the extraction solvent (Crank, 1975; Milojevic et al., 2008; Sovova,
2012).