Page:Indian Medicinal Plants (Text Part 2).djvu/421
N. 0. EUPHORBIACEÆ. 1171
Uses : — Officinal in both the Pharmacopœias, and its uses are too well known to be mentioned here.
" Leather has examined a large number of seeds from Madras, Bombay, United Provinces and Central Provinces, and shows that they contain from 25 to 35 per cent, of shells, and the kernels, with few exceptions, afford from 60 to 70 per cent, of oil, or 35 to 50 per cent, on the entire seed. Larger seeds as a rule contain more oil than smaller seeds.
Castor oil is a colourless or pale greenish oil having a taste at first mild, then harsh. The oil is very viscous, but does not dry even when exposed in thin layers. Most commercial samples contain only very small proportions of free fatty acids, this is due to the refining process which consists in the coagulation of albuminous matters by steaming and then removing them by filtration. Castor oil is strongly dextro-rotatory. Deering and Redwood examined twenty-three samples of Indian oil and observed that in a 200 mm. tube in a Hoffmann-Laurent polarimeter the variation was from+7.6 to +9.7°. Castor oil may be said to consist of a small quantity of tristearin, of the glyceride of dihydoxystearic acid, and to a large extent of the glyceride of ricinoleic acid.
The physical and chemical constants of the oil have been found as follows : Specific gravity at 155°, 0.963 to 0.964 ; saponification value, 177 to 184 ; iodine value, 81.4 to 85.3 ; Richert-Meissl value, M; Maumene test, 46-47; oleo-refractometer degrees at 22°, 41 to 42.5. Insoluble fatty acids : Melting point, 13° ; iodine value, 86 to 88.
The high specific gravity and acetyl value and its very high viscosity afford ready means of identification. It is also miscible in all proportions with glacial acetic acid and absolute alcohol, but is nearly insoluble in large quantities of petroleum ether, kerosene and higher boiling paraffn oils." (Agricultural Ledger, 1911-12 No. 5 pp. 164-165.)
Ricinin, C17H13N4O4 is the poisonous principle of the seeds. The pressed seeds yield 0.3 per cent., whereas the husks yield 1.5 per cent., of ricinin. To obtain the ricinin, the pressed seeds or husks are extracted with boiling water ; the extract evaporated on the water bath, and the residue treated with alcohol. The alcoholic solution is then evaporated to dryness and the residue treated with caustic soda ; by this means, the impurities are dissolved out, and the ricinin which remains behind may be crystallised from alcohol or water. It crystallises in glistening plates ; melts at 194°, has a bitter taste, is readily soluble in water, alcohol, chloroform, benzene and ether; the aqueous solution is neutral and optically inactive. Ricinin may be sublimed when carefully heated ; it is soluble in concentrated sulphuric acid, yielding a colourless solution, which becomes straw-yellow, and then bright claret red, on warming. The colourless sulphuric acid solution gives, with a crystal of potassium dichromate, a bright green coloration ; this is suggested as a test for ricinin. Ricinin does not give the usual tests for alkaloids, neither does it form salts with strong mineral acids ; it yields a bromo-derivative, C17H16Br2N4O4 , which melts at 247°, and a corresponding diloro-derivative, which melts at 240.° With mercuric chloride, it yields the compound, C17H13N4O4 , 2 Hg Cl7 , which melts at 204°, When oxidised, it yields a new acid, C15H14