Abstract: Key factor and mechanism influencing the content of unsaponifiable matter were investigated,during rosin analyisis using ether extraction from its soap solution. The morphological variation characteristics of resin acid, as well as titration correction of the unsaponifiable matter during rosin saponification were discussed theoretically. As results, there are the highest content of volatile matter in the unsaponifiable matter of masson pine rosin,high contents of unsaponifiable matter and volatile matter in slash pine rosin, and less contents of volatile matter in P.caribaea Morelet and P.latteri Masson rosins. The content of unsaponifiable matter becomes decreasing while drying temperature is increasing.On the contrast, acid values of the unsaponifiable matter of these 4 kinds of rosin get increasing because high drying temperature results in autoxidation of diterpene aldehydes. However, the acidity of the unsaponifiable matter would mainly originated from the ionization equilibrium between resin acid and its potassium salt. Therefore, the content of unsaponifiable matter must be corrected during rosin analysis.

Key words: unsaponifiable matter, rosin analysis, resin acid, ionization equilibrium