The Art of Perfumery, and Methods of Obtaining the Odors of Plants

The residue remaining from the evaporation of the alcohol is treated with water, which separates a fatty and resinous substance. The watery solution which contains the coloring matter is then precipitated by neutral acetate of lead. The precipitate, which possesses a beautiful green color, can be washed with plenty of water, and then decomposed with sulphuretted hydrogen; the coloring matter passes into the watery solution, which is carefully evaporated in a water-bath; the residue is again dissolved in absolute alcohol; and lastly, the alcoholic solution is mixed with ether, which precipitates the cyanine in the form of blue flocks. Cyanine is uncrystallizable, soluble in water and alcohol, insoluble in ether; acids, and acid salts color it immediately red; by alkalies it is, as known, colored green. Cyanine appears to behave as an acid, at least it forms with lime, baryta, strontia, oxide of lead, &c., green compounds insoluble in water. Bodies absorbing oxygen, as sulphurous acid, phosphorous acid, and alcohols, decolorize it; under the influence of oxygen its color is restored. We must here mention that Moroz has prepared a beautiful blue substance from Centauria cyanus by treatment with absolute alcohol. Rose-red Coloring Matter.--We have employed alcohol to extract the substance which colors rose-red certain dahlias, roses, poeonias, &c. For the procuration of this coloring matter the method pursued is exactly as that for the preparation of cyanine. By an attentive comparison of the properties of this coloring matter with those of cyanine, we have found that the rose-red coloring matter is the same as the blue, or at least results from a modification of the same independent principle. It appears in the rose-red modification, when the juice of the plant, with which it exists in contact, possesses an acid reaction. We have always observed this acid reaction in the juices of plants with red or rose-red coloration, while the blue juices of plants have always exhibited an alkaline reaction.