Labdanum Resin

#### Labdanum Resin. In strict accordance with our definitions, **Labdanum Resin **is the resinous matter from crude labdanum, soluble in hydrocarbon solvents but insoluble in alcohol. It is .a non-volatile and almost odorless matter. However, due to the method by which it is prepared, the resin usually carries some odor of the parent "gum". During the past few decades, labdanum has been subject to very thorough investigations in the sense that various attempts have been made to isolate the odorous matter and leave out the odorless portion. Extraction by selective solvent methods is now quite common. More simple is the two-step extraction. As an example, it can be mentioned that alcohol extraction, followed by petroleum ether extraction of the alcohol-soluble matter, yields one product, while petroleum ether extraction, followed by alcohol extraction of the petroleum ether soluble matter yields another product. Similar experiments have been carried out with benzene and other solvents. Obviously, it is preferable to perform the first extraction with a hydrophilic type of solvent (like alcohol) since the crude "gum" inevitably contains some moisture. Even a modest water content would act as an inhibitor on a hydrocarbon solvent extraction, and it can form emulsions which are difficult to break, etc. When **Labdanum **("gum") is extracted with benzene and the extract in turn is treated with alcohol, a resinous matter separates from the alcoholic solution. Similar precipitates are formed during petroleum ether/ethyl alcohol extraction of labdanum (this process yields a very light- colored absolute), or during other two-step extractions. In all these cases, a very dark, hard and resinous, almost brittle mass is separated. It has only a very faint odor and it particularly lacks the sweetness of the total labdanum. **Labdanum**** ****Resin**** **is used primarily to "cut" other labdanum extracts, e. g. for cost reduction. It also finds some use as a fixative in soap perfumes, detergent perfumes, industrial perfumes, etc. when its dark color and poor solubility do not prohibit its application. Unfortunately, the term "**Labdanum**** ****Resin**" is also applied to other products from labdanum or to the residue from the steam distillation of **Cistus Oil **(see this monograph) from Spanish labdanum "gum". The latter type of "labdanum resin" is superior to the above mentioned resin in respect to odor. An almost obsolete perfume material is the type of "**Labdanum**** ****Resin**" which is produced by destructive distillation (at atmospheric pressure) of crude labdanum.