953 



CITRIC GROUP. 



CITRUS AURANTIUM, ORANGE. 



954 



Itaconic acid (C 10 H O e ) occurs among the distillation products of 

 citric acid, and is derived from the decomposition of aconitic acid. 

 Citric acid is heated in a retort by means of a spirit lamp, until yellowish 

 vapours, and an oily liquid passes over, which solidifies to crystals 

 these are pressed and recrystallised from water. Its crystalline form 

 is a rhombo-hedral octohedron. It is inodorous, and has a strongly 

 acid taste. Tolerably soluble in cold, and much more so in hot water. 

 By heat it decomposes into anhydrous citraconic acid, and water. 

 C 10 H 9 = 2HO + C^H.O,, 



Itaconic acid. 



Anhydrous citraconic 

 acid. 



It is bibasic, and forms two series of salts : C^HjO^MO + HO) and 

 < , JI.O^MO. 



Citraconic A fid (C IO H 8 = C 10 H 4 ,2HO). In the later stage of the 

 distillation of citric acid an oily liquid passes over, which is anhydroiu 

 citrncon ic acid (C 10 H,O a ). When exposed to the air it attracts moisture, 

 and becomes slowly converted into a crystalline mass of citraconic acid 

 (C IO H 0,). Citraconic acid is isomeric with itaconic acid, but differs 

 from that substance in its crystalline form, which is a four-sided prism, 

 and also in being more soluble in water. Small quantities heated for 

 some time to 212 are converted into itaconic acid. Citraconic acid is 

 c, like itaconic acid, and forms two series of salts. 



i-ouii' aciJ, Citracartic acid (C 10 H e 8 ). When a weak solution 

 of citraconic acid is digested for some with about ^jth its volume of 

 nitric acid, the liquid deposits after some time crystalline masses, of an 

 aspect like porcelain, which when purified have the form of somewhat 

 brilliant needles, which sublime without alteration, and are very slightly 

 soluble in water, consist of mesaconic acid, and are produced by a 

 simple isomeric transformation of citraconic acid. Itacouic acid, when 

 acted upon by nitric acid, does not yield mesaconic acid. Mesaconic 

 acid is bibasic, and forms two series of well defined salts. 



The neutral ethers of these three isomeric acids, itaconate, citra- 

 rrmate, and nusaconale of ethyl, are also isomeric, and then- formula is 

 C 10 H,0,2C 4 H 5 0. They are all produced by dissolving the acid in 

 alcohol, and etherifying by means of hydrochloric acid. The two 

 former are oily aromatic liquids with a bitter taste, slightly heavier 

 than water. They boil at 437 Fahr. under partial decomposition. 

 Mesaconic ether has a pleasant fruity odour, it boils at 428* Fahr., and 

 distils without alteration. 



Brominated derivatives of the pyrocitric acids. By the action of 

 bromine on either neutral citraconate or itaconate of potash in the 

 presence of water, carbonic acid is evolved, and a yellow oil deposited 

 which is a mixture of two substances. The one is a heavy, neutral, 

 amber-coloured fluid ; its formula is C 6 H 3 Br 3 0, ! which is that of a 

 terbrominated acetone or terbrominated propionic aldehyde. The other 

 substance is bromotriconic acid, and can be separated from the mixture 

 by potash. Frequently, after standing, the oil solidifies to a mass oi 

 crystals. It forms salts. Its formula is C 8 H 6 Br 2 O t which is that of a 

 bibrominated butyric acid ; but its discoverer, M. Cahours, was not 

 able to prepare it from butyric acid. 



If bromine act on citraconate or itaconate of potash in the presence 

 of excess of potash, the reaction appears to take place in an analogous 

 manner, but the resultant product is an acid, Iromitonic acid 

 (C H Br a 4 ), or a bibrominated propionic acid. 



Chloride ofpyrocitryl (C 10 H,0,,CL). This substance is produced by 

 the action of pentachloride of phosphorus on anhydrous citraconic acid 

 It is a fuming, heavy, refringent liquid, which boils at 347 Fahr. It is 

 decomposed by water into hydrochloric and citraconic acids. 



The amides and anilides of the pyrocitric acids have been carefully 

 investigated by Gottlieb, to whose papers in Liebig's ' Annalen,' vols 

 77 and 85, the reader is referred for details. 



CITRIC GROUP. A family of organic compounds belonging to the 

 acetic series. It comprehends citric acid and its derivatives. The citric 

 group is attached to the acetic series by several reactions : for instance 

 citric acid gives by destructive distillation acetone, and when heatec 

 with hydrate of potash it is converted into acetate and oxalate o 

 potash. The following are amongst the principal members of this 

 group : 



Citric acid .... C^HgO^ 



Citramide . . . C^HnNjOg 



Aconitic acid C 12 H 6 O 1S 



Fvrocitric acid . . . . C 10 H|jO 8 

 Pyrocitramide . . . Cj H 8 N 2 O 4 

 Pyrocitramic acid . . . C 1|P H 7 NO 6 

 Pyrocitrimide .... C^HjNO, 



Citric ether C^HjO,,, 3C 4 H 5 O 



fitraconanile .... C 10 H 4 (C 12 H 5 )NO 4 

 Citracondinitranile . . . C, ^.(C^H^NO,) a (NO 4 



Citraconimide .... Ci H 5 NO t 

 Citruconiodanidc .... C 10 H 4 (C 1S H 4 I)N0 4 



For a detailed description of such of these bodies as are not men 

 tioned under their respective names, see Gerhardt's ' Traite" de Chimie 



vol. ii. p. 85. 



CITROBIANILE. [CITRIC ACID.] 

 CITROBIANILIC ACID. [CiTBio ACID.] 

 CITRONYL. [CiTREif.] 



CITRUS AURA'NTIUM, ORANGE, of which there are two 

 >ecies, the sweet, or China orange, Citrus Aurantium, Risso, and C. 

 ligaradia, Risso, and the bitter, or Seville. The fruit of the latter, 

 i-hile small and unripe, is collected and dried : the smallest, which are 

 E the size of a pea, are used for keeping issues open, and the larger for 

 IB preparation of the liqueur called Curacoa. Of the ripe fruit every 

 art is used either medicinally or dietetically. The rind, called flavedo, 

 ontains a bitter principle and much volatile oil ; and either used at 

 essert, or reduced to powder and added to magnesia and rhubarb, 

 urnishes a grateful tonic to the stomach in some forms of dyspepsia and 

 out. The pulp and juice are exceedingly agreeable to persons 

 ffected with inflammatory complaints, or a drink prepared from it 

 orangeade) is of great utility in bilious and gastric fevers, dysentery, &c. 

 "he roasted pulp forms an excellent application to fetid ulcers. 



The peel of lemons is likewise employed, but it is not so wann and 

 rateful as that of oranges, from containing less volatile oil. The 

 wwers of lemon juice are much increased by saturating it with 

 hloride of sodium (common table-salt). It is then of great efficacy in 

 he treatment of dysentery, remittent fever, the dry belly-ache, putrid 

 ore throat, and other diseases occurring in the West Indies. Dr. 

 Vright also recommends it in diabetes and lientery. Similarly mixed 

 i-ith table-salt, but without sugar, it is one of the best drinks against 

 ea sickness. 



Citric acid exists in numerous fruits, particularly those of the 

 >range tribe, such as the lemon and lime, either alone, or with malic 

 md other acids ; sugar, mucilage, and extractive are also present. The 

 itric acid is separated and purified on a large scale, in the way before 

 mentioned. [CITRIC ACID.] It is frequently adulterated with other 

 acids, such as tartaric, sulphuric, muriatic, and oxalic, which may be 

 letected by appropriate tests. Citric acid, when crystallised, has 

 carcely any odour, but a very distinct acid taste. It is soluble in cold, 

 jut more abundantly in warm water. Citric acid has the power of 

 nirdling the milk of most animals, but not the human milk. 



As it is impossible to treat of citric acid apart from lemon juice, we 

 Jass them together. The impression of both on the organ of taste is 

 ,he same in kind, but different in degree. Concentrated citric acid is 

 somewhat caustic, but lemon juice is gratefully acid. To imitate the 

 latural state, citric acid is only given largely diluted. In this state it 

 iroves a pleasant drink in fevers and diseases where the temperature of 

 ,he body rises above the natural standard. According to Broussais, it 

 agrees better than any other acid with the stomach when affected with 

 acute inflammation. It is not so pleasant as lemonade prepared from 

 new fresh lemons, and according to the statement of Sir G. Blane, the 

 solution of citric acid is not so efficacious in the prevention and cure of 

 sea-scurvy as the recent lemon juice. This is attributable to the 

 absence of the volatile oil and the bitter principle of the rind, which 

 ire valuable adjuncts to the citric acid in its action on the stomach. 

 The utility of lemon juice in promoting the digestion of gelatinous 

 meats, such as veal and turtle, is well known Fresh lemon juice may 

 je preserved in bottles in the same way as ripe fruits, by boiling the 

 aottles in which it is contained for half an hour, first placing them in 

 cold water, and gradually heating it, and as soon as the contents of the 

 bottles have fallen to the temperature of the air, closing them her- 

 metically. Where lemon juice so preserved, or fresh lemons, cannot be 

 obtained by ships on long voyages, the dissolved citric acid, to which a 

 portion of an alcoholic extract of lemon peel may be added at the time 

 of using, must serve as a substitute, should any apprehensions of 

 scurvy be entertained. Its efficacy as a daily drink, without sugar, 

 properly ^diluted, in improving the health of feeble children, is most 

 striking. 



Lemon juice is often a means of correcting acidity in the stomach, 

 since, like most vegetable acids, it elevates the vitality of that organ, 

 and prevents the formation of an excess of acid. On the same prin- 

 ciple it is found to be a useful agent in elevating the powers of the 

 stomach in the intermittent, remittent, and bilious fevers of America, 

 many cases of which have yielded to a combination of lemon juice, 

 cinchona bark, and port wine. Lemon-juice has been recommended 

 on theoretical grounds, in acute rheumatism and gout, in large doses 

 several times a day. Doubtless, its power in improving the condition of 

 the digestive organs, may render it useful in some cases of these disorders. 

 Lemon juice is often employed to rouse the stomach and nervous 

 system after narcotic poisoning ; but neither it nor vinegar should be 

 used till all the poisonous substance is evacuated from the stomach, 

 otherwise it increases the power of the poison. 



Citric acid, as well as lemon juice, is much employed to decompose 

 alkaline carbonates, forming therewith pleasant effervescing solutions. 

 These taken in the act of effervescence are .often of great utility in 

 checking vomiting, and in reducing the temperature in inflammatory 

 complaints. But in all cases of debility the employment of citric, or 

 any other vegetable acid, for this purpose, is decidedly improper. The 

 amount of injury done by the indiscriminate use of effervescing 

 draughts made with a vegetable acid is incalculable. " Were I re- 

 required," says Dr. Prout, " to name the medicine calculated to do the 

 most mischief, I should name the common saline draught formed of 

 potash or soda and some vegetable acid." 



Citric acid alone is very xiseful in the phosphatic diathesis ; it is 



the alkaline base in this combination which does harm. [CARBONIC 



ACID.] 



