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.
As the oil is speedily oxidized and vitiated by exposure to light, heat and air, it must be carefully preserved from these influences. This can be best accomplished by putting it up in vials or bottles immediately after filtration. These vials should be of such a size that when one is opened it will be consumed within a few days. The vials must be securely corked, and then sealed with wax or parafnne, or tied over with bladder. They are then to be preserved in a dark closet in a cool cellar. No vial is, under any circumstances, to be used for the second time, as the few drops of old oil remaining would act like a ferment, and turn the new oil rancid.
The United States Pharmacopoeia gives an excellent direction for the preservation of oil of lemon, which may be of value to those bottlers whose consumption of the article is limited. It consists in mixing one ounce of 95 per cent, deodorized alcohol with nineteen ounces of oil of lemon, and then decanting it after it has become clear from sediment. Another proposition to keep oil of lemon fragrant is the following:
To every pound of oil one ounce of alcohol is to be added, and well mixed; then one ounce of water is put with it, which again withdraws the alcohol from the oil and collects at the bottom of the bottle as dilute alcohol, where it should be permitted to remain until the oil has been used, with perhaps an occasional shake-up when the bottle has been opened. Oil of lemon treated in this manner has been kept fresh and fragrant for over a year. Oil of orange may be treated in the same manner with excellent effect.
With these precautions, an originally good oil of lemon, no matter of what, brand, maybe kept unimpaired for a reasonable length of time. Without them the best of oil will soon become rancid, terebinthinate (of the nature of turpentine) and utterly worthless. The exclusion of the atmosphere is accomplished by putting the oil in small glass vials, which should be almost completely filled, and then made air-tight. The actinic effect of the sunlight (that power of the sun's rays by which chemical changes are produced), which is manifested in the production of a photograph, is excluded by keeping the oil in total darkness. The equally baneful influences of an elevated temperature must be guarded against by selecting a closet in a cool cellar.