Lemon

LEMON (Fructus Citri recens) (from the Arabic limun), the fresh fruit of the lemon tree, Citrus medica L., subspecies Citrus Limonum (Risso) Hooker f 11., family Rutaceae Aurantiaceae. Homeland (according to Bonavita) - China and Cochin China. Species of sour lemons in the wild state are now found at the foot of the Himalayas and in India. The fresh ripe fruit of the lemon tree has a bright yellow shiny rind and represents a 10-12-locular berry 7-8 cm long and 5-6 cm wide, with a nipple-like elevation at the upper pole. The thin yellow skin of the fruit is studded with depressions containing numerous spherical glands filled with yellow essential oil. The middle layer of the pericarp (rind) is white, has no taste or smell. The segments are separated by the thinnest membranous partitions (endocarp) and each contains 2 seeds and a large-celled parenchyma filled with acidic juice containing 6-8% citric acid; the juice and pulp have no odor. The seeds are bitter in taste. Lemon contains a significant amount of vitamin C, much less vitamins A and B. In medicine, fresh lemon juice, fresh lemon rind, which is used to prepare lemon oil sugar (Elaeosaccharum flavedinis cort. citri), lemon essential oil, dried lemon rind, lemon acid obtained from the juice, and its salts are used. Lemon and lemon juice (formerly also lemon acid) are used as one of the best and most reliable remedies for scurvy. Lemon or its juice is often used with tea and water to quench thirst, especially in febrile patients. Lemon juice, in the absence of lemon acid or other acids, is successfully used as an antidote in cases of alkali poisoning. Externally, lemon juice is used as a prophylactic against bedsores by rubbing the juice into the skin in the appropriate places; it is also used as a face wash. Fresh lemon juice (Succus Citri recens) is pressed from the pulp of the lemon freed from the rind. The best juice is obtained from fruits weighing at least 100 g, having an elongated-oval shape, yellow color, and thin pericarp. One lemon yields on average 22 g of juice, a large lemon - up to 30 g. Lemon juice must contain at least 7.7% crystalline citric acid. Lemon juice was used (according to Leber) for acute articular rheumatism; lemon juice saturations with potassium bicarbonate (Potassii bicarbonas e Succo Citri rec. par.) were also prescribed. This results in a solution of potassium citrate, saturated with CO₂ and having a barely noticeable lemon aroma. According to some authors, applying lemon juice has a beneficial effect in cases of sunburn of the face, chest, etc. Hager states that when consumed in large quantities (100-500 g) of undiluted lemon juice, poisoning and even death may occur. - Lemon rind (Cortex Citri) is the dried pericarp of the ripe lemon. The outer surface of the lemon rind is yellow-brown, the inner surface is white; the taste is slightly bitter, with a weak aromatic odor. - Constituent parts: essential oil, hesperidin, aurantiamarin, tannin, mucus, salts of mineral and organic acids, ash (up to 3.6%); contains no citric acid. Fresh lemon rind is used to obtain essential oil by pressing or pricking; lemon oil can also be extracted with alcohol; by rubbing fresh lemon rind with sugar, Elaeosaccharum flavedinis cort. citri of our former pharmacopoeias is prepared. Lemon rind is rarely used as a stomachicum, carminativum. Citric acid (Acidum citricum) - C₆H₈O₇+H₂O or C₃H₄OH(COOH)₃+H₂O; synonym - oxitricarboxylic acid. Citric acid was obtained in crystalline form from lemon juice by Scheele in 1784, after Retzius in 1776 had established its difference from tartaric acid. The chemical nature of citric acid was first elucidated by Liebig and Pebal. Citric acid, both in the free state and in the form of salts, is very widespread in nature; it is found in cranberries (cranberry extract contains 25%), lingonberries, bird cherry, cherry, raspberry, gooseberry, blueberry, mulberry, tamarind, etc.; especially much citric acid is found in unripe fruits of Citrus medica, C. limonum and C. bergamia. Citric acid is also found in the roots, leaves, tubers, and bark of some plants. Combined with calcium, citric acid is contained in the amount of 1-1.5 g per 1 liter in cow's milk, in cheese, and in human milk. Citric acid is obtained synthetically: 1) from symmetrical dichloroacetone, converting it to dichloroacetone cyanohydrin, dichloroxyisobutyric acid, and dicyanooxyisobutyric acid, from which by boiling with hydrochloric acid citric acid is obtained; 2) by successive treatment of acetonedicarboxylic acid with hydrocyanic and hydrochloric acids. Furthermore, citric acid is formed in large quantities (up to 56%) during the fermentation of grape sugar with Citromyces glaber, C. Pfefferianus, Penicillium luteum and Mucor piriformis.-Citric acid is obtained from unripe lemons falling from the tree or from such ripe lemons that cannot be sold due to their appearance; the rind from such lemons is first removed to obtain essential oil. Lemon contains 6-8% free citric acid and insignificant traces of its salts. Citric acid crystallizes with one molecule of crystallization water (C₆H₈O₇ + H₂O) in large colorless rhombic prisms with a specific gravity of 1.617. Crystalline citric acid already melts at 70-75°, while anhydrous acid melts only at 153-154°. Citric acid dissolves in ³/₄ part of cold water and in ¹/₂ part of boiling water; from a saturated solution of citric acid at 100°, anhydrous crystals of C₆H₈O₇ are separated upon rapid cooling; the same happens if an aqueous solution of citric acid is heated to 130° and then cooled. In 90% alcohol, citric acid dissolves in one part, in ethyl ether - in 50 parts; when heated to 175°, citric acid converts to aconitic acid C₆H₃(COOH)₃. Citric acid and its salts dissolve in sulfuric acid without discoloration; browning occurs only when heated above 90° (difference from browning tartaric acid). If lime water is added to a solution of citric acid until an alkaline reaction occurs, no precipitate is obtained at ordinary temperature, but when heated to boiling, a precipitate appears, which dissolves again almost completely upon cooling. Citric acid, used for medical purposes or for the kitchen and table, must not contain calcium, lead, copper, iron, mineral acids, and foreign organic acids. An admixture of tartaric acid is detected by the precipitation of calcium tartrate when neutralized with lime water, as well as by the browning of a mixture of 1 g of citric acid powder with 10 g of concentrated sulfuric acid when heated below 90°, and also by the precipitation of cream of tartar in the citric acid solution when potassium acetate and alcohol are added. Citric acid is used internally in mixtures or lemonades and serves for preparing acid drinks. Of the salts of citric acid, the potassium salt is used, and in recent years especially often the sodium salt; both salts in the blood convert into bicarbonates and act as such. The salts are prescribed as diuretics, and in large doses - as laxatives. As a cooling agent, citric acid is used in doses of 0.5-1 g. Citric acid was also used as an analgesic in 5-10% solutions for cancerous tumors; it was also recommended for diphtheria in a 2% solution as a gargle. The use of citric acid in medicine is in many respects identical with the use of lemon juice. Citric acid is used for the quantitative determination of phosphoric acid (citrate method). A large amount of citric acid is used in calico printing as a mordant and to brighten colors. For medical sodium citrate, or citrate of soda, or sodium citrate (Natrium citricum), there are three kinds of salts: tribasic, dibasic, and monobasic. The tribasic salt C₆H₅Na₃O₇+3H₂O (Natr. citric, tribasicum), trisodium citrate, is obtained by neutralizing a concentrated solution of sodium carbonate with citric acid. Rhombic prisms do not effloresce; easily soluble in water. This salt is also known with 3 molecules of crystallization water in the form of hard, interconnected, efflorescing crystals. The dibasic salt C₆H₆Na₂O₇+H₂O (Natr. citricum dibasicum), disodium citrate, obtained by neutralizing 1 part of citric acid with sodium carbonate with the addition of 0.5 part of citric acid to the neutral solution. Star-shaped prisms; easily soluble in water.

The monobasic salt C_eH₇Na0₇ + H₂O (Natr. citricum monobasicum), monosodium citrate, is obtained in the form of aggregates of transparent, spear-shaped crystals when a solution of the trisodium salt of citric acid is mixed with a double amount of citric acid and allowed to evaporate; both anhydrous crystals and crystalline powder are obtained in this way. - The application of sodium salts of citric acid: in doses of 0.25-4 g as an antipyretic and diuretic in kidney and bladder diseases; previously used in typhus. In concentrated (30%) solution, the trisodium salt is used to reduce and stop bleeding. Conversely, weak 0.2-2% solutions reduce blood clotting and are used in blood transfusions and in laboratory practice to protect blood from clotting. Lemon oil, Ol. Citri, Ol. de Cedro, Ol. Limonis. The best lemon oil is obtained by squeezing the fresh peel of L. by hand over a sponge, or by destroying the oil glands of the peel on points over a special dish for collecting oil; the second method gives larger yields of oil (about 2-3%). Lemon oil is a light yellow liquid with a greenish tinge, mobile, with a characteristic pleasant odor and burning taste, neutral reaction; it ignites with iodine, whereas oil obtained by distillation with water does not ignite with iodine. Lemon oil essentially consists of a mixture of right limonene with 4.5-7.5% citral C₁₀H₁₆O and probably an equal amount of citronellaldehyde C₁₀H₁₈O or citronellal. In lemon oil from Messina, geranyl acetate (C₁₀H₁₇O-C_aH_sO) was found, and in lemon oil from Palermo there is also linalyl acetate (CH₈COO-C₁₀H₁₇). On prolonged storage, stearyoptene-citrene, or lemon camphor, separates from lemon oil. Pure lemon oil is transparent, light yellow in color, specific gravity 0.857-0.862 at 15° and soluble in alcohol; characteristic odor and taste; at 20° the rotation of the plane of polarization to the right varies from +57° to +61°. - Lemon oil is used as a perfume in ointments and rubs and as a flavor corrector, aromatic; it is a component of aromatic vinegar (F VII) and Hoffman's balm (F VII). Lemon oil is widely used in the manufacture of lemonade and is one of the main components in cologne, is used for flavoring food substances, is added, for example, to cookies, gingerbread, etc. Lemon syrup (Sirupus Citri), according to F V, is prepared by dissolving at gentle heat 3 weight parts of citric acid and 1 weight part of lemon oil-sugar in 150 weight parts of sugar syrup. Freshly prepared syrup slightly opalesces from the undissolved lemon oil. To obtain a perfectly clear lemon syrup, it is allowed to stand for 3-4 days and then filtered. Lemon syrup has a sour taste and aroma of L. It is prescribed as a flavor corrector in the amount of 10-20% by weight of the mixture.