Канадський бальзам

What it is

Canadian balsam (also called Canada balsam) is the oleoresin of Abies balsamea, the balsam fir of boreal North America. When the essential oils in which the resin is dissolved have been allowed to evaporate, it turns to a transparent yellowish mass. Canada balsam is amorphous when dried. It has poor thermal and solvent resistance. It is insoluble in water and miscible with benzene, chloroform and xylene.

The tree

Balsam fir is native to most of eastern and central Canada, from Newfoundland west to central Alberta, and to the northeastern United States. It is a small to medium-size evergreen tree, typically 14 to 20 metres tall. On young trees the bark is smooth and grey and bears resin blisters, which tend to spray when ruptured.

Chemistry

The oleoresin contains 27.5% volatiles (pinene, nopinene and β-phellandrene), 44.5% resin acid and 27% neutral resinous compounds. Among the resin acids are abietic acid (13%) and neoabietic acid (8%). Work on the oleoresin has isolated three new 3,4-seco-lanostane triterpenoids and one new cycloartane triterpenoid, along with fourteen known terpenoids. The balsam dissolves completely or almost completely in ether and turpentine oil, and about 90% of it dissolves in alcohol or petroleum ether.

Uses

Because its refractive index is close to that of crown glass, purified and filtered Canada balsam was traditionally used in optics as an invisible-when-dry glue for glass, such as lens elements. In biology it can conserve a microscopic sample, which is sandwiched between a microscope slide and a glass coverslip and glued in place with the balsam. In geology it is used as a common thin section cement and glue. In oil painting it is used to achieve glow and facilitate fusion. It is also used to make fine lacquers. For slide mounts, dried Canada balsam is dissolved in xylene or toluene, in approximately equal amounts of both. Some workers prefer terpene resin for slide mounts, as it is both less acidic and cheaper than balsam. The resin was traditionally used as a cold remedy.

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