This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
It has been asserted that oyxgen is so essential to the development of the odor of plants that it might be said to be the bearer of the aroma. Experiments proving this assertion were made known, but it is only within the last few years that the principle here evolved has been practically applied to the needs of manufacturing. These so-called oxygenated oils consist of two component parts separable by fractional distillation. The more volatile part is a camphene, and possesses so little odor that it can be and has been used to adulterate other essential oils. The heavier compound, containing oxygen, is the sole bearer of the peculiar aroma. These oils are claimed to be not only purer and more agreeable in both odor and taste, but are much stronger, and are very easily soluble in weak alcohol, perfectly transparent.
Manufacturers of liquors and cordials are said to find by the use of these patent oils a great saving of time and trouble, inasmuch as no clarification is necessary, provided the body is perfectly clear. For keeping, these concentrated oils require the same precautions as to light and temperature as the ordinary oils; and an addition of one-half per cent, of absolute alcohol serves to keep them better. The following strengths of these patent oils are given as compared with ordinary essential oils:
Angelica, thirty times stronger; anise, two times; bergamot, two and one-half times; calamus, ten times; cassia, two times; lemon, thirty times; coriander, six times; fennel, two times; caraway, two and one-half times; spearmint, two times; lavender, two and one-half times; cloves, two times; peppermint, two times; orange peel, thirty times; sassafras, two times; thyme, five times; which means that one fluid drachm of concentrated oil of angelica will flavor a barrel of diluted alcohol as strongly as thirty fluid drachms of the ordinary oil of angelica. These oils form clear solutions with sixty parts of seventy per cent, alcohol, and mix clear with eighty per cent, alcohol in all proportions.
From the above it must not be taken that bottlers are advised to use these concentrated, patented or artificial oils. Mention of them is given for cautionary purposes, for none but the purest essential oils should be employed in beverage making, no matter what specious claims are made for substitutes or adulterants.