DETECTION OF FOREIGN OILS IN SWEET BIRCH AND WINTERGREEN OILS

1. DETECTION OF FOREIGN OILS IN SWEET BIRCH AND WINTERGREEN OILS

For a rapid evaluation of the quality of sweet birch and wintergreen oils, the alkali solubility test often proves of value. (See also "Solubility," p. 252.)

Procedure:¹¹⁷ Introduce 2 cc. of the oil in a 25 cc. glassstoppered, graduated cylinder and add 23 cc. of an aqueous solution of potassium hydroxide prepared by dissolving 6.5 g. of potassium hydroxide (analytical grade) in sufficient distilled water to yield 100 cc. of solution. Shake thoroughly and permit the cylinder to stand undisturbed for 24 hr.: no oily separation should result, although a separation of a solid waxy material is indicative of a normal oil.

Since the natural waxy separation melts at a relatively low temperature, care should be exercised in interpreting the results of this test in warm weather.

It is well to study the odor of the solution or any insoluble portion. Since the potassium phenolate of methyl salicylate is practically odorless, additions of foreign, odor-bearing substances may be detected.

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177 This is a slight modification of the test described in "The United States Pharmacopoeia," Tenth Revision, 239.