Resin, terpene

The resin secreted by pine trees is called turpentine. From the chemical composition, turpentine is mainly a solution formed by dissolving solid resin acid in terpene. After turpentine is processed, volatile terpenoids are called turpentine, and non-volatile resin acid melts are called rosin. When rosin just flowed out of the resin channel of pine trunk, it was colorless and transparent, and the terpene content could reach 36%. After contact with air, terpenes volatilize rapidly, and at the same time, resin acid crystallizes, and rosin itself gradually becomes as viscous and semi-liquid as honey. Turpentine oil sent from forest areas to factories often contains various mechanical mixtures, including pine needles, bark, sawdust, insects and dust. Pinus massoniana turpentine generally consists of the following components:

72-75% rosin

Turpentine 16-20%

Moisture 4-6%

0.05-0.3% of impurities

When turpentine is at rest, resin acid crystals precipitate and sink from turpentine. The upper layer often presents a yellow liquid, which is composed of liquid terpenes and some substances that are difficult to crystallize. The content of turpentine in the upper liquid can reach 50%, and other substances are mainly oxidized resin acid.

If turpentine is exposed to air for a long time, turpentine gradually volatilizes and oxidizes, and some oxygen is transferred to resin acid, and turpentine turns yellow and dries. This turpentine is often called "hair rosin". The output and grade of rosin and turpentine obtained by processing crude rosin should be reduced. Therefore, the collected turpentine should be treated in time to ensure the quality of rosin and turpentine.

The purpose of turpentine is to remove impurities through processing and produce qualified rosin and turpentine through distillation. These two products are important industrial raw materials.