The drug has a place in all the early printed pharmacopœias.
Collection—Euphorbium is obtained by making incisions in the green fleshy branches of the plant. These incisions occasion an abundant exudation of milky juice which hardens by exposure to the air, encrusting the stems down which it flows; it is finally collected in the latter part of the summer. So great is the acridity of the exudation, that the collector is obliged to tie a cloth over his mouth and nostrils, to prevent the entrance of the irritating dust. The drug is said to be collected in districts lying east and south-east of the city of Morocco.
Description—The drug consists of irregular pieces, seldom more than an inch across and mostly smaller, of a dull yellow or brown waxy-looking substance, among which portions of the angular spiny stem of the plant may be met with. Many of the pieces encrust a tuft of spines or a flower-stalk or are hollow. The substance is brittle and translucent; splinters examined under the microscope exhibit no particular structure, even by the aid of polarized light; nor are starch granules visible.[2080] The odour is slightly aromatic, especially if heat is applied; but 10 lb. of the drug which we subjected to distillation afforded no essential oil. Euphorbium has a persistent and extremely acrid taste; its dust excites violent sneezing, and if inhaled, as when the drug is powdered, occasions alarming symptoms.
Chemical Composition—Analysis of euphorbium performed by one of us[2081] showed the composition of the drug to be as follows:—
| Amorphous resin, C₁₀H₁₆O₂ | 38 |
| Euphorbon, C₁₃H₂₂O | 22 |
| Mucilage | 18 |
| Malates, chiefly of calcium and sodium | 12 |
| Mineral compounds | 10 |
| 100 |
The amorphous resin is readily soluble in cold spirit of wine containing about 70 per cent. of alcohol. The solution has no acid reaction, but an extremely burning acrid taste: in fact it is to the amorphous indifferent resin that euphorbium owes its intense acridity. By evaporating the resin with alcoholic potash and neutralizing the residue with a dilute aqueous acid, a brown amorphous substance, the Euphorbic Acid of Buchheim,[2082] is precipitated. It is devoid of the acridity of the resin from which it originated, but has a bitterish taste.
From the drug deprived of the amorphous resin as above stated, ether (ether or petroleum) takes up the Euphorbon, which may be obtained in colourless, although not very distinct crystals, which are at first not free from acrid taste. But by repeated crystallizations and finally boiling in a weak solution of permanganate of potassium, they may be so far purified as to be entirely tasteless. Euphorbon is insoluble in water; it requires about 60 parts of alcohol, sp. gr. 0·830, for solution at the ordinary temperature. In boiling alcohol euphorbon dissolves abundantly, also in ether, benzol, amylic alcohol, chloroform, acetone, or glacial acetic acid.
Euphorbon melts at 116° C. (113° to 114°, Hesse) without emitting any odour. By dry distillation a brownish oily liquid is obtained, which claims further examination. If euphorbon dissolved in alcohol is allowed to form a thin film in a porcelain capsule, and is then moistened with a little concentrated sulphuric acid, a fine violet hue is produced in contact with strong nitric acid slowly added by means of a glass rod. The same reaction is displayed by Lactucerin (see Lactucarium), to which in its general characters euphorbon is closely allied.
Hesse (1878) assigns to euphorbon the formula C₁₅H₂₄O, and points out that its solutions in chloroform or ether are dextrogyrate.
As to the mucilage of euphorbium, it may be obtained from that portion of the drug which has been exhausted by cold alcohol and by ether. Neutral acetate of lead, as well as silicate or borate of sodium, precipitate this mucilage, which therefore does not agree with gum arabic.