Rectified Birch Tar Oil

#### Birch Tar. For perfumery purposes, only the rectified oil of Birch Bark Tar should be considered. The tar is produced from the bark of various birch species by slow destructive distillation. This tar is oily, almost black in color, and not quite homogeneous. Flakes of carbon, oil drops, etc. separate from the liquid. The crude tar is subsequently steam distilled, and yields a rectified birch tar which is sometimes called **Birch Tar Oil, Crude**. For many years, production was concentrated in the countries along the Baltic Sea, but only little birch tar is produced in these countries now. The U. S. S. R., Germany, Finland, and occasionally Sweden produce limited quantities. Unfortunately, the present-day product is often a mixture of wood-tar and bark-tar (see below). **Rectified Birch Tar **is a pale yellow to brownish yellow, clear and oily liquid. The odor description, "like Russian leather", is conventional, but somewhat incorrect. Russian leather smells of birch tar because the leather is tanned with the tar products which also preserve this special type of leather. This circle of odor association is similar to the well-known: vanillin smells of chocolate! The odor of **Birch Tar Oil **is distinctly phenolic, very penetrating and diffusive, obviously reminiscent of tar, charred wood and smoke (all of which have their odor from components of the birch tar oil!) However, the most characteristic feature in the odor pattern of birch tar oil is the sweet-oily undertone which appears distinctly on the smelling blotter when the first empyreumatic notes have faded away. These notes caught the immediate interest of perfumers long ago, and the chemists tried to isolate these particular fractions of the oil. A number of special "fractions" of rectified **Birch Tar **are available from the raw material suppliers; others are made by the users for their individual purposes. It seems almost certain that the typical sweet, oily and leatherlike notes are due to components in the non-saponifiable part of the rectified birch tar oil. In other words, the most interesting components are the non-phenolic ones. The tar from birch bark contains up to 80% of non-phenolic materials, while the wood tar has very little of these interesting components. Consequently, a sample of birch tar for processing into rectified birch tar oil should be chemically tested for content of non-phenolic components. The olfactory test is equally important, but it is extremely difficult to estimate the value of a birch tar exclusively by the odor of the crude tar. **Rectified**** ****Birch**** ****Tar**** ****Oil**** **has the additional advantage of being very pale and not discoloring with certain essential oils which would cause discoloration when mixed with phenols (patchouli, vetiver, copaiba balsam, etc.). The oil is easily soluble in alcohol, and does not impart an acid reaction to the perfume in which it is used. To the perfumer, this "heart" fraction of the birch tar oil is the true and highly appreciated sweet and powerful "leather" odor for fougères, chypres, "men's fragrances", after-shave lotions, modern fantasy bases, etc. The steam distilled birch tar can be alkali- washed free of phenols, and subsequently vacuum distilled to produce a pale straw-colored oil of delightful "cuir" note and tremendous diffusive power. The crude tar is used in pharmaceutical preparations, e.g. ointments, lotions, etc. for eczema and other dermatological diseases. **Birch**** ****Tar**** **is frequently adulterated with birch wood tar, beech tar (black and highly phenolic), pine tar (clear dark chocolate brown), juniper tar (**Cade Oil**) or even coal tar (naphthalenic odor). See also **Leather**.