Citrus medica, var. Limonum, (Risso) Hooker filius. The outer yellow rind of the fresh ripe fruit.

Habitat. N. India; cultivated in subtropics, Mediterranean Basin, United States (California, Florida), Australia, etc.

Syn. Limon. Cort.; Fr. Ecorce (Zest) de Citron (Limon); Citron, Limon; Ger. Cortex Fructus Citri, Flavido Corticis Citri, Citronen Limonen)--schale; Limone, Citrone.

Med'i-ca. L. Medicus, medical, curative -- i.e., properties useful in medicine.

Li-mon'um. L. a lemon, fr. Arab, limun, limu, taken from Skr. nimbuka.

Plant

Straggling bush or tree, 3-4.5 M. (10-15 degrees) high, more tender than the orange, having many angular branches and sharp spines in the leaf-axils; bark gray, that of branches green, of twigs reddish or purple; leaves evergreen, 5-6 Cm. (2-2 2/5') long, ovate, acute, serrate, 12 Mm. (1/2') petioles; flowers all the year round, sweet-scented, white to purplish-pink; fruit ovoid berry 7.5 Cm. (3') long with nipple-shaped extremity, smooth, depressed punctations over the oil-glands, structure like orange; pulp acid, yellow; seed as in orange, only smaller. PEEL, the outer, lemon-yellow, dark yellow layer, recently separated by grating, paring, and consisting of an epidermal layer, numerous parenchyma cells containing yellow chromoplastids, and large oil reservoirs with globules of the volatile oil; odor fragrant, distinctive; taste aromatic; sections mounted in a fixed oil show epidermal layer (small tabular cells), hypodermal layer containing numerous plastids, a mesocarp with colorless, thin-walled parenchyma, large elliptical oil reservoirs, granular protoplasm, calcium oxalate crystals. The inner spongy white portion should be removed and discarded. Solvents: alcohol; wine; water. Dose, 3ss-1 (2-4 Gm.).

Citrus medica, var. Limonum: a, flower; b, fruit.

Commercial

Lemons reach us from California, Florida, W. Indies, Mediterranean region (Sicily, Spain, etc.) packed in boxes, each lemon being wrapped in white or brownish tissue-paper. Foreign varieties are known as wax, imperial, gaeta, and all, when kept several months, deteriorate, owing to the decomposition of citric acid, into sugar and carbon dioxide, in consequence of which, to insure preservation and permit long shipments, they must be coated with melted paraffin, dissolved shellac, or varnish. The rind should be pared thinly from the fruit with sharp knives and carefully dried.

Constituents

Volatile oil, bitter principle, hesperidin, ash 4 p.c.

Oleum Limonis. Oil of Lemon. U.S.P. -- (Syn., Ol. Limon., Lemon Oil, Oleum de Cedro; Fr. Essence (Huile) de Citron -- Cedrat; Ger. Citronol, Limonenol.) This volatile oil is produced mostly in Sicily, S. France, Italy (Calabria), by expression from fresh peel of the ripe fruit, using several processes that rupture mechanically the oil-cells thereby liberating the oil and rendering it easily collected: 1, spugna -- collecting by sponge the oil from ruptured cells of the quartered rind; 2, scorzetta -- of the halved rind; 3, machina -- substituting a complicated machine for manual labor of expression and collection; 4, ecuelle a piquer -- not much used but consisting of an instrument, bowl-shaped, 25 Cm. (10') wide, of tinned-copper, having a raised opening in the center which forms with the outer edge a broad channel; to this there is a heavy cover similarly shaped, whose inner surface as well as that of the machine is armed with concentric rows of short 6 Mm. (1/4') spikes or ridges; an opening in the bottom allows the escape of oil. By a handle the cover is made to revolve rapidly one-half minute over the instrument, having between the two 5 to 8 fruits, after which they are replaced by fresh ones. About 7000 fruits can be exhausted daily by each machine. It is a pale yellow, greenish-yellow liquid, characteristic odor and taste of the outer part of fresh lemon peel, sp. gr. 0.853, dextrorotatory, soluble in alcohol (3), dehydrated alcohol, carbon disulphide, glacial acetic acid; neutral, slightly acid; contains at least 4 p.c. (7-8) of aldehydes calculated as citral, CHO, which gives the aroma and value (being also produced by oxidizing geraniol, CHO, with chromic acid), limonene (citrene), C H, 76 p.c., little cymene, C10H14, citronellal, CHO, phellandrene, pinene, geranyl acetate, a sesquiterpene, octyl aldehyde, nonyl aldehyde, methyl heptenone, terpineol.  Should be kept cool, dark, in completely filled, well-stoppered, amber-colored bottles, and that having a terebinthinate odor must not be dispensed.  Dose, mj-5 (.06-.3 cc.).

Adulterations

Oils of other Citrus fruits, fixed oils, alcohol, oil of turpentine.  The fragrant Oil of Petit Grain Citronnier, from immature fruits, leaves, and twigs, closely resembles Neroli Petit Grain, and may be used similarly.

Hesperidin, CHO. -- A glucoside (bitter principle) from the white, spongy part or rind by boiling water; bitter, yellowish-white powder or white needles; soluble in diluted alkalies or acetic acid, black with ferric salts, and by diluted sulphuric acid decomposed into hesperetin, CHO, and glucose, CHO.

Preparations

I.  PEEL: 1.  Tinctura Limonis.  Tincture of Lemon.  (Syn., Tr. Limon., Tinctura Limonis Corticis; Fr. Teinture d'Ecorce de Citron; Ger. Citronenschalentinktur.)

Manufacture: 50 p.c. Similar to Tinctura Cardamomi Composita, p. 137 -- macerating 50 Gm. in alcohol 100 cc., filtering through purified cotton, and finishing with alcohol q.s. 100 cc.  Dose, 3ss-2 (2-8 cc.).

Preps.: 1.  Syrupus Acidi Citrici, 1 p.c.  2.  Emulsum Petrolati, N.F., 1.5 p.c.

II. OIL: Liquor Magnesii Citratis, 1/10 cc. In 350.  2.  Spiritus Ammoniae Aromaticus, 1 p.c.  3.  Spiritus Aurantii Compositus, 5 p.c.  4.  Acetum Aromaticum, N.F., 1/10 p.c.  5.  Linimentum Terebinthinae Aceticum, N.F., 1.6 p.c.  6.  Mistura Oleo-Balsamica, N.F., 2/5 p.c.  7.  Spiritus Odoratus, N.F., 4/5 p.c.  8.  Syrupus Eriodictyi Aromaticus, N.F., 1/20 p.c.  9.  Syrupus Sennae Aromaticus, N.F., 1/7 p.c.

Unoff. Preps.: PEEL: Spirit, 5 p.c., + oil 5 p.c. (alcohol), 3ss-2 (2-8) cc.).  Infusion.  Syrup.  Juice (from fruit--used alone,  neutralized by alkali, or made into syrup; soon spoils, but will keep a short time byletting stand until albumin is coagulated, straining into hot bottles, and covering with almond or sweet oil; flavor is preserved best by making it into concentrated syrup); yield 1/2-1 ounce (15-30 cc.) per lemon, dose, 3ij-5 (8-20 cc.).

Properties And Uses

Stimulant, stomachic, added usually to infusions, tinctures, etc., chiefly for flavoring.  Juice refrigerant, relieves thirst, febrile inflammatory affections in agreeable beverages; diaphoretic (neutral mixture), scurvy (seamen on long voyages should take 3j (30 cc.) daily as a preventive, acute rheumatism; locally in sunburn, pruritus of scrotum, uterine hemorrhage after labor, gargle in diphtheria.

Limones, Lemons.  The fruit, U.S.P. 1820-1850.  Limonis Succus, Lemon Juice, U.S.P.  1860-1900.