_Heliotropin_ or _piperonal_ is of great importance in the manufacture of perfumes. It forms small, colorless prismatic crystals, which have an agreeable odor of héliotrope. Upon the tongue heliotropin produces the same sensation as oil of peppermint under the same conditions, the sensation being, however, more lasting. It melts at about 104° F., and volatilizes at a higher temperature without leaving a residue. It is soluble in alcohol and ether, and insoluble in cold water; in hot water it melts to an oily liquid which floats upon the water. Exposed to the action of heat and air, heliotropin acquires an uncomely appearance, balls together and, under very unfavorable circumstances, turns brown. It is then entirely decomposed and useless, and, hence, should be kept in summer in as cool a place as possible. A temperature of 95° F. has already an injurious effect upon the perfume, and it is best not to buy it at all in the hot summer months. To preserve the perfume in its entire freshness, it is advisable for consumers in hot climates to at once dissolve the heliotropin in alcohol and to keep the solution in a cool place. Pepper serves as the initial point for heliotropin or piperonal, the white variety being the best for the purpose. To obtain piperine, contained in varying qualities (7 to 9 per cent.) in pepper, the latter is repeatedly extracted with boiling alcohol. The extract is then evaporated to one-third its volume, or the greater portion of the alcohol is distilled off, and the resinous mass, obtained after the addition of water, is repeatedly washed in water with the addition of a small quantity of potash or soda lye, dissolved in alcohol and purified by repeated recrystallization. To convert the white-yellow piperine thus obtained into potassium piperate it is, together with equal parts of potassium hydroxide and 5 to 6 parts of alcohol, kept gently boiling for 24 hours in a well-closed flask provided with an ascending Liebig cooler. A capacious flask should be used, as the mass pounds quite vigorously. After cooling, the precipitate, which is obtained in yellowish, lustrous lamina, is separated through a filter from the dark-brown mother-lye, washed with cold alcohol and several times recrystallized from hot water. A further discoloration may be effected by the addition of animal charcoal. The potassium piperate thus obtained forms nearly colorless prisms in verucose groups, which, however, turn yellow when exposed to light. By boiling the alcoholic mother-lye with ⅓ of the previously used potash-lye, further small quantities of potassium piperate may be obtained.