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.
Cutting essential oils is called the process of mixing them with some very finely powdered substance to the consistency of a paste in order to be absorbed and divided into very small particles, offering a comparatively large surface to the action of the solvent, and thereby rendering them more readily soluble by the addition of alcohol, and yielding on diluting with water and filtration a clear solution called "Essence," which is miscible with aqueous liquids and yields clear aromatic waters.
Essential oils that are dissolved in strong alcohol in order to prepare a concentrated essence, say one ounce of oil in sixteen ounces of alcohol, do not yield a clear aromatic water. Beverages prepared with such a concentrated essence attain a "milky" appearance, owing to the partial separation of essential oil. The use of magnesia in cutting essential oils is quite familiar with the carbonators. It has been recommended to them time and time again.
On page 470, under "Formulae for Clarifying Powders," we have already urged the carbonators to dispense with its use, and repeat it here. For alcoholic liquids or solutions, the calcined, as well as the carbonated magnesia, are familiarly known clarifying powders, since both are insoluble in alcohol and have no action on it whatever. However, they exert an action on aqueous, or aqueous-alcoholic liquids (diluted alcohol), such as we employ in cutting essential oils. Carbonate magnesia is almost insoluble in water, requiring, according to Fyfe, 2500 parts of cold water; calcined magnesia requires, according to Fresenius, 55,000 parts of water for solution. However, both, when employed in conjunction with the diluted alcohol (or as is the case with syrups, which are aqueous solutions) to facilitate and dissolve essential oils, impart to the liquid an alkaline reaction that has a noticeable effect upon the delicate flavors of the oils, and in some cases their employment would even be attended with some loss of flavor. Ta obviate the risk of deterioration and impairment to such flavors by the use of magnesia various other means of cutting essential oils have been proposed.
Calcium phosphate, kieselguhr and diatom earth (erronously called infusorial earth - both are silicious earths), have been employed. The former is not very suitable and can never be employed where fruit-acids enter into the cutting process to form a part of the essence, as quite a quantity of calcium phosphate would be dissolved by them. Both of the others frequently contain large quantities of iron, the Virginia specimen more than double that of the German, and are therefore very objectionable, unless thoroughly purified from iron in the manner explained on page 623 for Talcum. Talcum is recommended as forming a most efficient and unexceptionable material for cutting essential oils, being a great absorbent, but it is a siliceous magne-sian mineral, and we propose to reject it on the same ground as we do magnesia.
Talcum also contains iron, and whenever used should be treated as before directed. In its purified state it is much less objection able for cutting oils than magnesia, having a great absorbent power Powdered artificial pumice stone we consider the least objectionable, it being very porous and a great absorbent. Finely powdered glass-sand and asbestos may also be used.
In the latest Pharmacopoeia (1887) cotton is directed as an absorbent and distributor of the substance to be dissolved, and it yields excellent results in regard to clearness and saturation. To employ this means, use for each ounce of oil one and one-half to two ounces of absorbent cotton. Pour the oil on the cotton a little at a time, and then pick the cotton apart with the fingers, so as to evenly distribute the oil. Then pack loosely in a percolator, and pass the dilute alcohol through the cotton. The cotton thus used may be dried, and can then be employed again. But we have still other means of cutting essential oils.
A familiar way is also to dissolve one ounce of oil in sixteen ounces of strong alcohol of 95°. Use a half-gallon bottle. This is a "concentrated essence," and would turn the beverage slightly milky. To avoid this, pour by degrees an equal volume of water into the bottle, frequently and briskly shaking. The essence will have turned quite milky - looking like an "emulsion.*' Then clarify it with paper pulp as directed on page 459. This of course will be a weaker essence, consequently double or three times as much is employed as of a more concentrated one. The paper-pulp may economically be rinsed with some strong alcohol, and this filtrate separately received for preparing the next lot. Another way is: Instead of with paper-pulp, shake the liquid up with about three to four ounces of pulverized pumice stone, and filter, returning the first runnings.