Balsam of Canada

Balsam of Canada, a resin obtained from North American fir trees (Abies balsamea, A. canadensis), is used in microscopy, due to its refractive index being equal to that of glass, for 'mounting' microscopic specimens. B. of C. has an acidic reaction and dissolves well in benzene, turpentine, xylene, chloroform, terpineol, cedar oil, bergamot and other essential oils. It is partially soluble in ethyl alcohol, carbon disulfide, and acetone; n_D (refractive index) = 1.541. In a thin layer it hardens into a solid colorless mass; for mounting microscopic specimens it is used in solution with xylene or chloroform; when the acidic reaction of B. of C. may damage the staining of the specimen (e.g., in staining according to Giemsa), neutral B. of C. is used, for which a solution of B. of C. in terpineol is employed. For mounting in B. of C., it is necessary to completely remove water from the specimen with absolute (ethyl) alcohol, replace the alcohol with an essential oil or other substance that easily dissolves the balsam, and then transfer to B. of C. Even traces of water cause clouding in the specimen. Adding 4 parts of piperine raises the n_D of B. of C. to 1.657.