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Balsam (also: turpentine) is the resinous exudate (or sap), which forms on certain kinds of trees and shrubs. Balsam (from Hebrew bosem בֹּשֶׂם, "spice", "perfume") owes its name to the biblical Balm of Gilead.
Balsam is a solution of plant-specific resins in plant-specific solvents (essential oils). Such resins can include resin acids, esters, or alcohols. The exudate is a mobile to highly viscous liquid and often contains crystallized resin particles. Over time and as a result of other influences the exudate loses its liquidizing components or gets chemically converted into a solid material (i.e., by autoxidation).
Resins are difficult to classify because of their amorphous nature. Even the term "resin" is not sharply defined. Several attempts were made to differentiate between waxes and other classes of substance, particularly fats, resins, and high molar mass polymers, by using several criteria. These primarily physical definitions are to some extent arbitrary and are not generally accepted.
Plant resins are sometimes classified as mixtures with other plant constituents, for example as pure resins (guaiac, hashish) gum-resins (containing gums/polysaccharides), oleo-gum-resins (a mixture of gums, resins and essential oils), oleo-resins (a mixture of resins and essential oils, e. g. capsicum, ginger and aspidinol), balsams (resinous mixtures that contain cinnamic and/or benzoic acid or their esters), and glycoresins (podophyllin, jalap, kava kava).
The liquid balsam called Balsam of Mecca is extracted from the tree Commiphora gileadensis (synonym: Commiphora opobalsamum) It is designated in the Bible by various names: bosem, besem, ẓori, nataf, and, in rabbinic literature, kataf, balsam, appobalsamon, afarsemon. It was used as a perfume and as a drug.
It was extracted both as the volatile component of the sap of the tree, and by boiling the stems and leaves. It was the only tropical, and the most expensive, spice grown in Israel. It was known to Pliny (Historia Naturalis 12:116; 13.18) as opobalsamum.
|Wikisource has the text of the 1911 Encyclopædia Britannica article Balsam.|
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