Preparations: Lemon Juice - Spirit of Lemon - Syrup of Lemon - Tincture of Lemon Peel
Related entries: Aurantii Amari Cortex (U. S. P.)—Bitter Orange Peel - Aurantii Dulcis Cortex (U. S. P.)—Sweet Orange Peel - Aurantii Flores.—Orange Flowers - Oleum Bergamottae (U. S. P.)—Oil of Bergamot - Oleum Aurantii Corticis (U. S. P.)—Oil of Orange Peel - Oleum Limonis (U. S. P.)—Oil of Lemon - Acidum Citricum (U. S. P.)—Citric Acid

The rind and juice of Citrus (Limon) Limonum, Risso (Citrus medica, var. B., Linné).
Nat. Ord.—Rutaceae.
ILLUSTRATION: Bentley and Trimen, Med. Plants, 54.
OFFICIAL PARTS.—I. LIMONIS CORTEX (U. S. P.), Lemon peel. "The rind of the recent fruit of Citrus Limonum, Risso (Nat. Ord.—Rutaceae)"—(U. S. P.).
II. LIMONIS SUCCUS (U. S. P.), Lemon juice.—"The freshly expressed juice of the ripe fruit of Citrus Limonum, Risso (Nat. Ord.—Rutaceae)."

Botanical Source.—The lemon tree is an evergreen, about 15 or 20 feet in height, with branches easily bent. The leaves are alternate, ovate-oblong, usually serrulated, smooth, glossy, and dark-green, with a winged petiole. The flowers are middle-sized, white, purple externally, and odoriferous. The calyx and petals are similar to those of the orange. The fruit is an oblong-spheroid, sometimes almost globular, with a thin, pale-yellow rind and a juicy, very acid pulp (L.).

History, Description, and Chemical Composition.—This plant, as well as those varieties of it producing the citron and the lime, is of Asiatic origin, and cultivated in the West Indies, and some other tropical countries. The exterior rind of the lemon and the juice of its pulp are official. The finest lemons are those which are smoothest and thinnest in the skin.

LIMONIS CORTEX (U. S. P.).—The rind, or lemon peel, as officially used, is described by the U. S. P. as occurring "in narrow, thin bands or in elliptical segments, with very little of a spongy, white, inner layer adhering to them; outer surface deep lemon yellow, and ruggedly glandular; odor fragrant; taste aromatic and bitterish. The spongy, inner layer usually present in the segments should be removed before the lemon peel is used"—(U. S. P.).

Lemon peel imparts its properties to alcohol, wine, or water. These depend upon a volatile oil contained in the minute vesicles with which it is filled, and, when obtained by distillation with water, or by expression, it forms the oil of lemon of commerce (see Oleum Limonis). The white portion of the rind contains hesperidin (C22H26O12), a bitter, crystalline glucosid, splitting, when heated with diluted acids, into glucose and hesperetin (C16H14O6) (see Aurantii Amari Cortex). The seeds of the fruit contain bitter limonin, soluble in cold alcohol, almost insoluble in water.

LIMONIS SUCCUS (U. S. P.).—Lemon juice, according to the official description, is "a slightly turbid, yellowish liquid, usually having an odor of lemon, due to the accidental presence of some of the volatile oil of the rind. Taste acid, and often slightly bitter. Specific gravity not less than 1.030 at 15° C. (59° F.). It has an acid reaction upon litmus paper, due to the presence of about 7 per cent of citric acid. On evaporating 100 Gm. of the juice to dryness, and igniting the residue, not more than 0.5 Gm. of ash should remain"—(U. S. P.).

One part of brandy or alcohol added to 10 parts of lemon juice, and then filtered to separate the mucilage, will preserve the acid for a long time; it will become slightly bitterish, but retains its strong acidity undiminished. The juice is frequently preserved in sugar, forming lemon syrup, which, however, is apt to spoil by age. Hence, citric acid in solution may be substituted for it, about 4 drachms of the acid being dissolved in 8 fluid ounces of water, which may be flavored with a few drops of oil or essence of lemon. Ɣ The strained juice has been preserved for some time by putting it into a bottle, and pouring upon it a layer of sweet, or almond oil. The juice may be concentrated by gentle evaporation or by freezing. All methods, however, are rather unsatisfactory, the juice either spoiling or becoming altered in flavor. Lemon juice, as stated above, contains about 7 per cent of citric acid; furthermore mucilage, malic acid, and salts of potassium and calcium are present. However, its proportion of acid is rather variable. As high as 44 grains of citric acid to the ounce of juice were obtained by Stoddard.

Action, Medical Uses, and Dosage.—Lemon peel is used in cookery and confectionery, and also in medicine to correct the taste and augment the power of bitter infusions and tinctures, its virtues being similar to that of the orange peel. The juice of lemon is tonic, refrigerant, and antiscorbutic, forming a refreshing and agreeable drink, called lemonade, possessing some medicinal influence, and which, as with orange juice, may be used freely and advantageously in the febrile and inflammatory diseases, with reddened mucous membranes, for which this last has been recommended. It may also be added to the nutritive drinks of the sick, as gum-water, gruel, barley-water, etc. Its power in preventing and arresting scurvy is unequaled by any other remedy, except a liberal supply of fresh vegetables of the cruciform family. In scurvy, an ounce or an ounce and a half of the juice per day, is a preventive dose, and when the disease manifests itself, 4 or 6 ounces per day will arrest it. Occasionally, but rarely, it fails to effect any benefit in this disease. Ships about to make long voyages, should be furnished with a bountiful supply of citric acid and oil of lemon, or lemon syrup, with a small portion of brandy added. Scrotal pruritis and uterine hemorrhage have been benefited by a local application of the juice. Ɣ Prof. A. J. Howe, M. D., states that although chloroform will arrest a paroxysm of hiccough temporarily, yet, if a permanent subsidence of the spasmodic action of the stomach and diaphragm be required, lemon juice is superior to all other known remedies; in several instances he has cured obstinate and dangerous hiccough with it. Both citric acid and lemon juice appear to exert considerable influence in preventing or modifying Asiatic cholera. When the mucous membranes and tongue are very red and the urine alkaline, rheumatism is benefited by lemon juice. One or two daily applications of lemon juice with a camel's-hair pencil will reduce enlarged uvula and tonsils. It also temporary relief in hoarseness, and has benefited some cases of malaria.

Specific Indications and Uses.—Fevers and inflammations, with very red membranes; rheumatic pain, with very red tongue and mucous tissues and alkaline urine; obstinate hiccough; scurvy; and should be given a trial in Asiatic cholera.

Related Varieties.Citrus acida, Roxburgh. The lime is a tree about 8 feet in height, with a crooked trunk and diffuse branches with prickles. Leaves ovate, obovate, oblong, and serrate, being placed upon petioles not winged as in the orange and lemon. Flowers small, white. Stamens 30. Fruit ovate or roundish; pale-yellow, with a boss at the point, and about 1 ½ inches in diameter. Cysts in the rind concave. Pulp very acid, flat, slightly bitter.

The lime is of considerably less size than the lemon, globular or oval, of a similar color, but frequently with a green or greenish tinge. Its outer coat is not so thick and rough as that of the lemon, and its internal pulp contains a large amount of juice of an excessively acid taste. This juice is chiefly used in the manufacture of citric acid. A variety of the lime tree, C. Limetta, furnishes a fruit from the rind of which is obtained the Oil of Bergamot. (For varieties of Lime, see below.)

De Candolle (Origin of Cultivated Plants) gives Citrus medica, Linné, as the name of the tree giving rise to the varieties, lemon, lime, citron, etc., and gives as such varieties those four enumerated by Brandis and Sir Joseph Hooker, viz.:

I. Citrus medica proper, or the CITRON of the English (cedro of the Italian, and cédratier of the French). The fruit of this variety is oblong and large, not spherical, has an aromatic, lumpy rind, and a juice neither very acid nor very plenty. This is the Citrus medica of Risso.

II. Citrus medica Limonum, the LEMON.

III. Citrus medica acida, Citrus acida, Roxburgh.—Juice very acid, fruit small and of variable shape, and flowers small. The LIME, SOUR LIME. Citrus acris, Miller, and other varieties, probably furnish a part of the sour limes.

IV. Citrus medica Limetta (C. Limetta and C. Lumia of Risso), SWEET LIME.—Fruit spherical, with non-aromatic, sweet juice.

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.