195 



OXALIC ACID. 



OXANILIC ACID. 



186 



shown that sublimation takes place even at common temperatures ; at 

 212' the volatilisation is much more considerable ; and when deprived 

 of two-thirds of its water of crystallisation, it sublimes rapidly and 

 without decomposing ; the sublimed acid is crystalline, and contains 

 one equivalent of water. 



When oxalic acid retaining the whole of its water of crystallisation 

 U suddenly heated up to about 300, it yields carbonic acid, carbonic 

 oxide, formic acid, and water. 



Oxalic acid forms compounds with bases, which are termed oxalates, 

 and of these we shall describe some of the more important. 



Of alaU of ammonia. [AMMONIUM, oxalate of ammonia.] 



Binoxalate of amm'mia may also be formed, but it ia not of im- 

 portance. When binoxalate of ammonia is heated it yields oxamic 

 acid (C,H 3 N0 ). 



Oxalate of potash (KO, C,0 3 , Aq.) Oxalic acid forms three salts with 

 jxjtash : the neutral oxalate is obtained by saturating the acid with the 

 alkali. It crystallises in flat rhombic crystals, which are so very 

 soluble in water, that even when cold the latter takes up half its weight. 

 When a solution of oxalic acid is added to this, precipitation of a less 

 soluble supersalt occurs. 



Jlin'jjcaluteofpotouk (KO, HO, 2C 2 0, + 2Aq.) may be prepared either 

 by dissolving the requisite quantities of acid and alkali in water, or, as 

 above mentioned, by adding oxalic acid to the neutral salt. It forms 

 small rhombic crystals, which have a bitter taste and an acid reaction ; 

 they are soluble in about 10 times their weight of cold water. This 

 Bait, mixed with the quadroxalate, exists in oxalit acetottlla, and they 

 constitute the compound know by the name of the tall of turret, 

 or salt of lemons, employed for removing ink-spots. 



Quadroxalate '/ potaik (KO, 3HO, 4C,0 3 + 4Aq.) may be formed by 

 digesting the binoxalate in hydrochloric acid, which taking half the 

 potash, the remainder becomes quadroxalate; or by saturating car- 

 bonate of potash with oxalic acid, and then adding three times the 

 weight of oxalic acid already used. The crystals are prismatic, and 

 are as little soluble in water as those of the binoxalate. 



The oxalates of potash are all converted by a red heat into carbonate 

 of potash ; their composition was first ascertained and pointed out by 

 Dr. Wollaaton as affording one of the most remarkable series of proofs 

 of the doctrine of multiple proportions. 



Oxalate and binoxalate of soda may be formed, but they are not 

 employed. 



'ate of lime (CaO, C,0 3 , 2Aq.) is a very insoluble compound, and 

 hence oxalic acid and lime, with certain restrictions, are used as tests of 

 each other's presence. Baryta and strontia also form insoluble com- 

 pounds with oxalic acid. The remaining metallic oxalates of importance 

 are noticed under the respective metals. 



Oxalic ether, or oxalate of ethyl (c.O, j ^'H'O) " best obtamed ty 

 allowing a slow stream of absolute alcohol to flow into a retort con- 

 taining oxalic acid in a state of fusion, a ad from which the water has 

 been mostly driven off. The distillate is sashed with water, in which 

 it is only slightly soluble, and finally dr'sd ovar chloride of calcium. 

 IU specific gravity is V0929 ; vapour density, 5'1 ; boiling point, 363-2" 

 Fahr. It is miscible with alcohol or ether. Potash and soda decom- 

 pose it, and ammonia converts it into oxamide. Potassium transforms 

 it into carbonic ether with evolution of carbonic oxide. 



Amyloxalic acid, or oxalamijlic acid (C,0 -{ 5" n) "> formed on 

 treating amylic alcohol with excess of oxalic acid. 



Tati for itj-alic acid. The best is the production of a white pre- 

 cipit.ite (oxalate of lime), with any soluble calcium salt, insoluble in 

 acetic acid, but soluble in hydrochloric acid. 



OXALIC ACID, the most highly oxygenated of all the vegetable 

 acida, is also the most rapid and certainly fatal of any which are 

 capable of being crystallised. As the crystals are not unlike those of 

 the sulphate of magnesia, or Epsom salts, mistakes between the two 

 are of very frequent occurrence. Being likewise much used in the arts, 

 and commonly known by the name of acid of tugar, it is taken either 

 accidentally, or under the supposition that it is akin to sugar, and 

 therefore pleasant and innocent. 



To prevent confusion of the crystals of this formidable acid with 

 those of the sulphate of magnesia, it has been proposed that the former 

 hould be coloured while in the course of preparation, an expedient 

 which has not been adopted. But on the other hand, the crystals of 

 Epsom salts have been manufactured of a different shape by a peculiar 

 process of crystallisation. The taste is very different, a solution of 

 oxalic acid being intensely BOUT, while that of sulphate of magnesia 

 is extremely bitter. Attention to this point, in previously tasting a 

 small quantity, may prevent very serious casualties. Oxalic acid not 

 only acts with violence, but produces nearly the same effects to 

 whatever texture of the body it is applied. The concentrated acid, if 

 taken in considerable dose, may cause death in from two to twenty 

 minutes. " After death the stomach is found to contain black extra- 

 vasated blood, exactly like blood acted on by oxalic acid out of the 

 body ; the inner coat of the stomach is of a cherry-red colour, with 

 streaks of black granular warty extravasation ; and in some places the 

 surface of the coat is very brittle and the subjacent stratum gelatin- 

 ued. Such are the effects of the concentrated acid. When con- 

 siderably diluted the phenomena are totally different. When dissolved 



in twenty parts of water, oxalic acid, like the mineral acids in the 

 same circumstances, ceases to corrode ; but, unlike them, it continues 

 a deadly poison, for it causes death by acting indirectly on the brain, 

 spine, and heart. The symptoms then induced vary with the dose. 

 When the quantity is large, the most promiuent symptoms are those 

 of palsy of the heart ; when less, fits of violent tetanus ; and when 

 still less, the spasms are slight or altogether wanting, and death occurs 

 under symptoms of pure narcotism, like those caused by opium." 

 Very few persons have recovered when the quantity taken was con- 

 siderable. (Christison, ' On Poisons.') 



To counteract the very rapid effects of this poison, the most prompt 

 treatment is necessary. Chalk, magnesia, or even the plaster of the 

 room diffused through water, should be given without delay. The 

 other alkalies are improper, as they form soluble salts with the acid, 

 and oxalic acid is an example of a poison which acts through all its 

 soluble chemical combinations. Emetics may be given, if vomiting 

 has not spontaneously taken place ; but it is highly inexpedient to 

 give much warm water, as dilution only facilitates the absorption of 

 the poison, and induces its remote but equally fatal effects. 



Notwithstanding the formidable properties of this acid, the agreeable 

 cooling effects it displays have led to its employment in the form of 

 lozenges, or in a dilute solution as a refrigerant. Both in this country 

 formerly, and still in France, it is used to quench thirst, and allay the 

 heat of the stomach, which prevails towards the later stages of consump- 

 tion. But for this purpose citric acid or lemonade is preferable, as 

 well as safer. 



Besides the immediate danger from an over-dose, there is yet a 

 remote source of risk which requires notice. Oxalic acid exists in 

 many vegetables, in combination with liine or potass, or free, as in the 

 case of the cicer arietiuum. Many of these plants are used in differ- 

 ent parts of the world, as salads, on account of their refrigerating 

 quality. Their frequent employment by persons disposed to calculous 

 diseases is highly dangerous, as they give rise to the formation of the 

 mulberry or oxalate of lime calculus, which is not only the most pain- 

 ful of all the stones found in the human kidneys or bladder, but also the 

 most insidious, for, owing to the insolubility of this compound, no 

 deposit or sediment is observed in the urine at an early period, so 

 as to occasion a suspicion of what is taking place. (Majendie, ' On 

 Gravel,' 2nd French edit.) [CiCEB.] 



The now well-ascertained connection between the existence of the 

 oxalic acid diathesis, rheumatism, indigestion, and other painful diseases, 

 renders a popular knowledge of this point of much importance. Not only 

 the free use of some of the vegetables alluded to, but saccharine fruits, 

 sugar, and starch, especially potato starch, give rise to the formation 

 of oxalic acid, and its attendant evils. Rhubarb (ttalks, not puwder), 

 sorrels of different sorts, tomatoes, common barberry, should all be 

 avoided by persons prone to rheumatism or stone in the bladder. Hard 

 Waters, containing lime, should be eschewed. The excessive use of 

 sugar, either in the ordinary states, or in sweet preserves, is improper. 

 Where any calculus of this sort is detected in the bladder, the employ- 

 ment of bicarbonate of potass in solution gives great relief, by coating 

 the very angular stone with a smooth surface. Its use must not be 

 top long persevered in. (See 'Prout on Stomach and Renal 

 Diseases.') 



OXALMETHYLOVINIDE (C 10 H 8 O a ). Oxalate of ethyl and methyl. 

 An ethereal salt of oxalic acid containing both ethyl and methyl. Its 

 constitution is similar to that of oxalic ether. [OXALIC ACID Oxalic 

 Ether.] 



OXALOVINIC ACID. [ETHYL; Ethyl-oxalic Acid] 



OXALURANILIDE. [URIC ACID.] 



OXALURIC ACID. [URIC GROUP.] 



OXALYL (C ; 3 ). The hypothetical organic radical contained in 

 oxalic acid, which is generally regarded as the hydrated oxide of 



OXAMELANILE (C^HnNjO,). Melanoximide. An unimportant 

 organic compound, produced by the transformation of cyano-melaniline 

 under the influence of acids. 



OXAMETHANE (C^NO.). Synonymous with oxamate of ethyl. 



OXAMETHYLANE (C H N0 ). Synonymous with oxamate of 

 methyl. 



OXAMIC ACID. [OXALIC ACID.] 



OXAMIDE (C 4 H,N S 4 ). A white pulverulent organic compound 

 produced by the action of heat upon oxalate of ammonia. By the 

 similar action of heat upon the oxalates of the artificial organic bases, 

 a number of bodies analogous to oxamide are produced. The following 

 may serve as examples : 



Dinwthyloxamide C,II,N,O 4 



Diethyloiamide c ijH, a N,O t 



Diamyloxamide C jH Jt N, ! 4 



Pbenyloxamide or oxanilamide . . . . C lft H B N 2 O 4 

 Diphenyloxamide or oxanilide . . . C S9 II 12 N 2 O 4 



OXAMYLANE (C. t H. 3 N0 ). Synonymous with oxamate of amyl. 



OXANILAMIDE. [OXAMIDE.] 



OXANILIC ACID <C 1( ,H,NO.). Phenyl-oxamic Acid. Anorganic 

 acid analogous to the oxamic acid, containing phenyl in the place of 

 one equivalent of hydrogen. 



