Lastly, tannic acid is present in the leaves under notice; their aqueous infusion is nearly colourless, but assumes a violet hue on addition of ferrous sulphate. After a short time a reddish precipitate is produced, which quickly turns blue. By using ferric chloride, a bluish black precipitate immediately separates.
Adulteration—The leaves of Vaccinium Vitis-idæa L., called Red Whortleberry or Cowberry, have been confounded with those of bearberry, which in form they much resemble. But they are easily distinguished by being somewhat crenate towards the apex, dotted and reticulate on the under surface and more revolate at the margin.
Uses—An astringent tonic used chiefly in affections of the bladder.
EBENACEÆ.
FRUCTUS DIOSPYRI.
Indian Persimmon.
Botanical Origin—Diospyros Embryopteris Pers. (Embryopteris glutinifera Roxb.), a middle-sized or large evergreen tree, native of the western coast of India, Ceylon, Bengal, Burma, Siam, and also Java.[1469]
History—The tree, which is mentioned in the earliest epic poems of the Sanskrit literature under the name of tinduka,[1470] was also known about the year 1680 to Rheede, and was figured in his Hortus Malabaricus.[1471] The circumstance that the unripe fruit abounds in an astringent viscid juice which is used by the natives of India for daubing the bottoms of boats, was communicated by Sir William Jones to Roxburgh in 1791. The introduction of the fruit into medicine, which is due to O’Shaughnessy,[1472] has been followed by its admission to the Pharmacopœia of India, 1868.
Description—The fruit is usually solitary, subsessile or pedunculate, globular or ovoid, 1½ to 2 inches long, and as much as 1½ inch in diameter, surrounded at the base by a large and deeply 4-lobed calyx. It is of a yellowish colour, covered with a rusty tomentum; internally it is pulpy, 6-to 10-celled, with thin flat solitary seeds. The fruit is used only in the unripe and fresh state; the pulp is then excessively astringent. At maturity, in the month of April near Bombay, the fruit becomes eatable, but is very little appreciated.
Chemical Composition—No analysis has been made of this fruit, but there can be no doubt that in common with that of other species of Diospyros, it is, when immature, rich in tannic acid. Charropin (1873),[1473] who has examined the fruit of the American D. virginiana L., found it to contain a tannic acid which he considered identical with that of nutgalls, besides an abundance of pectin, glucose, and a yellow colouring matter insoluble in water but dissolving freely in ether.