To obtain piperonal from the potassium piperate, dissolve 1 part of the latter in 40 to 50 parts of hot water, and then slowly introduce, with constant stirring, a solution of 2 parts potassium permanganate in 50 parts of water. This precaution is absolutely necessary, as otherwise the piperonal formed would be partially further oxidized and lost. The paste-like mass formed is passed, while still hot, through a straining cloth, and the residue repeatedly washed with boiling water until it shows nothing more of the characteristic odor of héliotrope. The wash-waters are combined with the first filtrate, and subjected to distillation over a free fire. The first distillates are richest in piperonal, it generally separating already in the cooler. The fractionally caught distillate is allowed to stand one or two days in as cool a place as possible, whereby the greater portion of the piperonal separates in a crystalline form or in fine lamina. To obtain the piperonal still remaining dissolved in the water, the mother-lye, after the separation of the crystals through a filter, may be repeatedly agitated with ether, whereby the piperonal dissolves in the ether. The latter is carefully distilled off at as low a temperature as possible (104° to 122° F.) in the water-bath or allowed naturally to evaporate. _Vanillin._--Vanilla is the not entirely ripe, pod-like, capsular fruit (wrongly called pod), of a tropical orchid (_Vanilla planifolia, Andrews_), which is cultivated in Mexico, the West Indies, and South America. It is extensively used for flavoring, and its odoriferous substance is highly valued in perfumery. The cross-section of the capsule is thick and fleshy, filled with very small, black, lustrous seeds stuck together by a gummy balsam with which they are coated. The capsule has a sourish taste and has no value, the seeds, or rather the balsam enveloping the seeds, being the substance on which the odor and taste of vanilla depend. When the vanilla fruit becomes ripe, the capsule opens and empties its content of seeds in the form of a balsam-like mass. The lustrous black-brown surface of vanilla is frequently coated with white, delicate crystals, which were formerly taken for benzoic acid. Bley and Vee first recognized them as a peculiar substance, which was further examined by Gobley and Stokkebye. This substance, to which Gobley applied the term _vanillin_, is the chief odoriferous substance of vanilla. It is deposited upon the vanilla-crystals, when the latter are densely and closely packed together and for some time exposed to a heat of about 77° F. Of vanillin, vanilla contains 1.5 to 2.75 per cent.; the Mexican variety containing 1.69 to 1.32 per cent., the Bourbon No. I, 2.48 to 1.91 per cent., Bourbon No. II, 1.55 to 0.75 per cent., and the Java, 2.75 to 1.56 per cent. It is singular, that the highly valued Mexican vanilla has, generally speaking, a lower content of vanillin than the other varieties.