Red Resins Known as Dragon's Blood.
BY J. J. DOBBIE AND G. G. HENDERSON.
Besides the red resins from Pterocarpus Draco and Croton Draco, there are three different recognized kinds of dragon's blood, one from the East Indies, Calamus Draco. one from Socotra, and one from the Canary Islands, Dracaena Draco. The first of these is the only one that has been fully described, but the results are not concordant; this is due apparently to the researches having been carried out on different substances. The authors have now investigated this subject, and have examined several varieties of the so-called dragon's blood, which they find can be arranged in four distinct groups:
- Those which dissolve completely in chloroform, carbon bisulphide, and benzene;
- Those soluble in chloroform, but insoluble in carbon bisulphide and benzene;
- Those soluble in chloroform and benzene, and partly in carbon bisulphide; and
- Those which are insoluble in all three reagents.
The accuracy of this classification is supported by the physical properties of the resins and their behavior towards reagents, and it is evident, therefore, that there were four different kinds of resins under examination. All the resins dissolve to a small extent in boiling water, those of Class 4 being rather more soluble than the others; they are all freely soluble in alcohol, ether, oil of cloves, and glacial acetic acid, leaving a variable amount of insoluble matter, which usually consists of vegetable tissue, sand, etc. They are all slightly soluble also in hydrochloric acid, those of Class 2 being the most soluble; ammonia reprecipitates them from this solution. The aqueous and alcoholic solutions have an acid reaction. When treated with sodium hydroxide, the resins effervesce and emit an odor like that of rhubarb. Ammonia forms a clear mixture with the alcoholic solutions. The resins were carefully purified by means of ether, and then powdered; the results of the individual class examinations may be thus summed up: Resin, 1, brick-red, melting at about 80°, when decomposed by heat gives off very irritating red fumes. It dissolves readily with an orange-red color in alcohol, ether, chloroform, carbon bisulphide, and benzene, but with difficulty in boiling caustic soda, ammonia, sodium carbonate, and with great difficulty in lime-water, whilst, in the cold, it is scarcely soluble in the first two and insoluble in the last two of the latter reagents. The ammonia solution is reddish-yellow, and a portion of the resin is not dissolved. The alcoholic solution gives a brown-red precipitate with lead acetate. Analysis (combustion and lead estimation) suggests the formula C18H18O4. This variety is derived from Calamus Draco. Resin 2, C17H19O5, origin uncertain, is carmine-red, melting at about 100°; when heated it gives off non-irritating fumes. It dissolves freely in alcohol, ether, and chloroform with a pink color, and in cold caustic soda, ammonia, sodium carbonate, and lime-water with purple color changing to orange-red or yellow on boiling, whilst it is insoluble in carbon bisulphide and benzene. The alcoholic solution gives a lilac-colored precipitate with lead acetate. Resin 3, C18H18O4, from Dracaena, is vermilion, melting at about 80°; when heated it evolves aromatic irritating red fumes. It dissolves with a blood-red color in alcohol and ether, and in cold caustic soda, ammonia, lime-water, and sodium carbonate, but is insoluble in chloroform, carbon bisulphide,. and benzene. Its alcoholic solution gives a mauve-colored precipitate with lead acetate. Resin 4, is a mixture of a reddish-brown resin,, freely soluble in carbon bisulphide, and a light brick-red resin, nearly insoluble in that menstruum. The two portions differ considerably with regard to their solubility in ether, benzene, and other reagents,. the dark portion being the less soluble of the two. Cinnamic acid was detected in the first and third varieties but not in the others. Johnstone found two resins in one kind of dragon's blood, to the one he gave the formula, C20H24O4, and to the other, C20H21O4.—Phar. Jour. and Trans. , 14, 361-364; Jour. Chem. Soc., April, 1884, p. 462.