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.
An approved and probably the safest and best method is to triturate one ounce of the oil in a mortar with two ounces of powdered artificial pumice-stone and two ounces of powdered sugar until all the oil is absorbed. Then add by degrees eight ounces of alcohol of 95° and after all is dissolved add also by degrees eight ounces of water, agitating it briskly all the time, then filter through filtering paper. Return the first runnings or repeat filtration until the essence is perfectly clear, which will then be water soluble. The oil and sugar combine to oil sugar, the powdered pumice stone acts also as an absorbent and on diluting as clarifyer. In this case also the powder remaining on the filter may be rinsed with strong alcohol in order to save some fine particles of oil retained therein. This filtrate is received separately and employed by the next operation. This essence can be made in advance, and will keep in well-stoppered bottles.
Some carbonators prefer to cut or rather dissolve the oil for immediate use without the aid of alcohol, in order to save the latter.
A mixture of pumice-stone and granulated sugar, in proportions sufficient to absorb the whole of the oil, is put into a mortar, the oil poured on it and all rubbed well together; then enough water is added to dissolve the oil-sugar, the pumice-stone clarifying the liquid on filtering.
This method may be employed when the syrup is prepared by the cold process. In this case we are rather in favor of using an abundance of sugar for the absorption of the oil, and would recommend to afterwards use plenty of water. The best way with this method would probably be to add some water to the mixture in the mortar after it has been thoroughly combined, agitate it with the pestle, pour on a filter (best into a felt or flannel-bag), and rinse the remaining part on the filter with the whole quantity of water required for that batch of syrup in order that it might take up as much of the aroma as possible; repeated returning of the runnings would prove advantageous. But even if these precautions are taken, part of the oil will separate and remain undissolved on the filter and will be lost, unless dissolved by pouring some alcohol on the residue in the filter.
We prefer the preceding method of cutting essential oils; the essence obtained by that process imparts unquestionably a richer flavor to the beverage than this aromatic water. When expensive oils are employed, the previous method is the most economical; and also when the hot syrup process is adopted, as the flavor would evaporate with the aqueous vapors on boiling. With but gentle heating, such aromatic waters do not suffer and impart their aroma to the syrup. However, we would not rely on its sole flavoring facilities, as the syrup, when diluted with the carbonated water, will not flavor as much as a syrup that has itself been flavored with an essence. The carbonator is in this case his own judge.
Tartaric or citric acid is believed by some carbonators to "cut" oils. This is an error. The fruit-acids serve for imparting an acidulous taste to the beverage, and have nothing at all to do with cutting the oils.