Some interesting researches have been instituted to ascertain,
- a. Whether the croton oil contains within itself an acid volatile at a low temperature?
- b. Is this acid the principle of its action, and can it be preserved if it be separated from the oil, and diminished if it be allowed to evaporate?
In order to answer both questions, the following operations have been instituted by this chemist.
The seeds of croton, deprived of their husks, ground at the mill, and subject to pressure, yield a certain quantity of oil.—If the residuum be mixed with double its quantity of alcohol and pressed again, it yields a liquid which is a mixture of oil {173} and alcohol. This liquid, when distilled, will yield more oil. Both oils are filtered, after having been allowed to settle.
The produce of this first operation is the natural croton oil, such as it exists in the seeds, which is of a brown amber color, viscid, having a peculiar smell, and possessed of great acidity, by which if applied to the skin, it produces an irritation varying in intensity according to its quantity, and the duration of time during which it has been applied. One drop, for instance, causes a blister in twelve hours.
If a piece of litmus paper be dipped in this oil, it turns red, and re acts acid; and the red color, though not deep, resists the action of the air and of a hot furnace.
The oil obtained by distillation from a solution in alcohol is rather more dark, viscid, and acid, than that obtained by simple expression.
The blue paper dipped in the oil obtained by distillation, reddens, and retains the color under the same circumstances as the former.
The second operation, however, offers already a fact which is of great value in deciding the question about the acidity of the croton oil. If you dip the litmus paper in the fluid which is gained by distillation, no traces of a change of color is visible; when, on the other hand, if you dip it in the oil which remains in the distilling apparatus, it changes the color as quickly as if dipped in the oil previous to distillation. The same is the case if the residuum is again acted upon with water or alcohol, the distilled fluid has no traces of acidity.
However, since the contrary opinion is entertained by good authorities, we must add other facts in corroboration of our own.