On Preservation of the Oils of Orange and Lemon.
To the Editor:
Showing a friend, a few days ago, some oil of lemon, which I had kept fresh and fragrant for over one year, he urged me to communicate the process to the Journal for publication.
The operation is as follows: To every pound of oil 1 oz. of alcohol is to be added, and well mixed; then 1 oz. 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.
The oil I have treated in this manner was in a large quart bottle, hardly more than half full, and is to day as nice as when first purchased.
In trying to explain to myself the theory of this action, the oil was closely observed, and a resinous film was found floating on the surface of the dilute alcohol. Whether the separation of this resinous film preserves the fragrance of the oil, or whether the presence of water has so good a result, I have not yet determined, but am certain that the general theory of deterioration by contact with air does not hold good in this case. Precisely the same effect was observed with oil of orange, and it was an agreeable surprise to find the experiment work so with both oils.
I would like to add, that the resinous film observed seemed to be in much larger quantity in the oil of orange, and for that reason I think this is the true cause of its spoiling more rapidly than the oil of lemon.
I send you a sample of each of the oils.
Very respectfully, CARL FRUH.
Philadelphia, April 6th, 1871.
Remarks by the Editor. The fact that a small amount of alcohol added to the volatile oils of the aurantiaceae preserves them, is known to many wholesale druggists, as well as pharmacists, and for many years we have preserved these volatile oils by the addition of 1 oz. of alcohol to a pound of the oil. The subsequent addition of a small quantity of water probably does not entirely remove the alcohol dissolved in the volatile oil. We would suggest to the author to continue his experiments and ascertain how much alcohol remains with the oil. It is very probable that the removal of foreign resinous and other matters has the effect of retarding oxidation by the atmosphere.