Alcohol is added either by itself or in the form of saturated solution of storax, benzoin, or Canada balsam, by which means the specific gravity of the balsam is but slightly changed. Bring the above-mentioned common salt solution, together with 20 grammes of the Peru balsam to be examined, into a small flask, and distil off about 5 grammes; gradually mix the distillate with 5 drops of caustic potash lye and potassium iodide solution saturated with iodine, shaking gently until the mixture acquires a slightly yellow-brownish coloration. If this coloration does not disappear in one minute, add drop by drop more of the potash lye until discoloration appears. In the presence of alcohol, yellow crystals of iodoform, which are readily recognized under the microscope by their form, collect on the bottom of the fluid. Adulteration with a volatile oil is recognized in the distillate by odor and taste. Fat oil, Canada balsam, copaiba balsam, gurjun balsam, and volatile oil may be recognized by the following tests: If pure Peru balsam in a porcelain saucer is thoroughly mixed with an equal volume of pure concentrated sulphuric acid, the mixture thereby becomes heated, vapors of a pungent odor being emitted, and if then set aside to cool, it congeals. In the presence of fat or volatile oils, copaiba balsam, gurjun balsam, or Canada balsam, it remains, however, more or less thickly fluid or more or less soft-smeary. If the balsam be pure, the cold mixture, after washing with water, should yield a hardish or soft-friable mass, which, when kneaded with the fingers, should not prove smeary or sticky. Fat oils are also very readily recognized by the use of warm petroleum-ether. The extract is evaporated, saponified with potash lye, extracted with alcohol, evaporated and decomposed with hydrochloric acid. A mixture of cinnamic acid and any of the fatty acids present in the Peru balsam is thereby obtained, which, after treatment with water, remains in the residue.