Page:Popular Science Monthly Volume 52.djvu/101

Rh if there were not some reason for preferring grease. Most of the substitutes recommended have more liberal affinities than grease. Alcohol, for instance, unites readily with water, and with water takes substances held in solution by it, which are extremely undesirable in a perfume; and so with the other substances, according to their several properties. Grease has a narrow elective affinity, and takes just what is wanted and nothing else. Various petroleum substances have been proposed recently as extractors, and much may be said prima facie in favor of them; but experiments with them have not yet given satisfactory results.

In the process of absorption or enfleurage wooden frames furnished with glass bottoms are used. These, fitting closely together, are placed one upon another, so that a small inclosed space is left between every two of them, or a sort of greenhouse with glass above and below, inclosed with wood. The surfaces of the glasses are coated with grease, on which a layer of flowers is placed. The flowers are left there to shed their perfume, which is absorbed by the grease, for twenty-four hours, when they are removed and new flowers are put in their places. This is continued for two or three months, at the end of which time the pomade is ready for treatment as in the maceration process. The flowers to which this process is best adapted are the jasmine, tuberose, and mignonette. This enfleurage process has likewise drawn criticism, if not contempt, from men of science; and the question has been asked why a different treatment is given to these from that pursued with other flowers.

If we observe flowers with regard to their odors, we shall find that they may be divided into two categories: those which contain their perfume already formed, or have at least a considerable reserve of it, and those which have no reserve, but develop and emit their fragrance as they grow. When we rub roses or orange blossoms, for example—flowers of the former class—we perceive their fragrance very plainly. Such flowers may be treated by distillation, by the warm pomade process, or by extraction with volatile solvents, with results of a greater or less degree of perfection, but always positive; while if we rub a flower of jasmine, convallaria, or violet—which are of the second class—we perceive nothing but a slight pungent odor in the same plant which an instant before was exhaling a pervading fragrance. In crushing it we have killed it, and it produces no more perfume. Such flowers are not suitable for distillation or maceration or the action of volatile solvents, because there is nothing to be extracted from them.

The production and exhalation of odor go on while the plant continues to live and vegetate, even after it has been cut. When, therefore, it is placed in the limited atmosphere of these absorbing