This section is from the book "Monograph on Flavoring Extracts With Essences, Syrups, and Colorings", by Joseph Harrop . Also available from Amazon: Monograph On Flavoring Extracts With Essences, Syrups And Colorings.
This oil, from which the extract is produced, comes next in importance, as a flavoring, to vanilla, because so extensively used.
Oil of lemon is a volatile oil, separated by mechanical means from fresh lemon peel, which is the rind of Citrus Limonum, Risso; specific gravity, 0.850; soluble in two parts of alcohol. It may be preserved from the effects of oxidation by mixing it, while fresh, with five (5) per cent. of alcohol and separating the oil after it has become clear. Keep in a cool place.
As mankind is divided into different races so, commercially, oil of lemon is divided into different grades; these, however, unlike the former, only remain separate for a short period and do not, perhaps, continue so after they have left second hands. They are sometimes called "select," "extra," "prime," or "fair," with prices to suit the different kinds, higher or lower, as you ascend or descend the scale. In buying, buy the best; good may mean very little; the best is none too good.