TARTARIC ACID. 



TARTARIC ACID. 



so 



announcement was made that tartaric acid had been artificially formed 

 in another and totally different manner, but on optically examining it, 

 the product proved to be racemic acid, a modified tartaric acid described 

 farther on. 



Tartrates. Tartaric acid is bibasie, and its salts consequently are 

 either acid (MO,HO,C 5 H 4 O lo ) or neutral (2MO,C,H 4 10 ). The neutral 

 salts may contain two similar or different protoxides ; or a protoxide 

 and a sesquioxide ; or a protoxide and a teroxide. They are mostly 

 formed by partially or wholly saturating the acid with the oxide or 

 carbonate of the oxide ; or, in the case of double tartrates, by satu- 

 rating a bitartrate with an oxide different to that already contained in 

 it. Heated in the air, tartrates blacken and give off an odour 

 resembling that of burnt sugar. The chief tartrates are noticed in the 

 following paragraph. 



Tartrate of Ammonia (2NH 4 0,C 9 H 4 10 ) is a very soluble salt; efflo- 

 rescent, and losing ammonia when exposed to the air. Bitartrate of 

 ammonia, (NH 4 O,HO,C,H,O lo ) is a crystalline powder tolerably 

 soluble in hot water though but very slightly so in cold water. 

 Tartrate of potash. (2K.O,C 9 H,0 10 ) crystallises with difficulty. Bitar- 

 trate of potash (KO,HO,C 9 H 4 10 ) was referred to at the commence- 

 ment of this article : one part is soluble in 240 of water, at 50" Fahr. 

 Heated to redness in a covered crucible it is decomposed, carbonate of 

 potash and charcoal being left in a fine state of division ; it con- 

 stitutes the black flux of metallurgists. Sometimes it is deflagrated 

 with nitre ; in this the carbon is all oxidised, and white flux (carbonate 

 of potash alone) is the name given to the residue. Tartrate of soda 

 (2NaO,C t H t 10 + 4 aq.) resembles the corresponding potash salt. 

 Bitartrate of soda (NAO,HO,C 8 H 4 IO + 2aq.) is far more soluble than 

 bitartrate of potash. A solution of it made by neutralising a given 

 quantity by carbonate of soda, and then adding a second similar 

 quantity of acid to the solution forms, if it be saturated, a useful 

 test of the presence of potash in a liquid, the bitartrate of the latter 

 base being formed and precipitated if present in notable quantity. 

 Ammonio-ttirtrate of soda contains (NH 4 O,NaO,C,H 4 0, +8aq.) Tar- 

 trate of potash, and soda (KO,NaO,C,H 4 10 ) is a laxative saline used in 

 medicine. It is sometimes called sel de Leignette from the name of 

 its discoverer who resided (1692) at Rochclle, hence also its name of 

 Rochelle salt. In former times it was called sal polychrest (that is salt 

 of many virtues). It is made by neutralising bitartrate of potash with 

 carbonate of soda. Tarlrate of lime (2CaO, C,H.O 10 +8aq) and 

 bitartrate of lime (CaO,HO,C 9 H 4 10 ) occur native. Tartrate of 

 (2CuO,C B H 4 10 + 8 aq.) is a bright green crystalline powder. 

 Tartrate [of ammonia and iron (NH,0,Fe I O s ,C 8 H 4 O 10 , + 4 to 6 aq.) 

 and Tartrate of < potash, and iron', (KO, Fe^Oj, C,H 4 10 ) are used in 

 medicine. They do not crystallise, but their) solutions dry up when 

 exposed on sheets of glass or other polished surfaces, and 1 scale 

 off in dark-red or brown laminae. Tartrate of potash and boron 

 (KO, BOj.CsHjO,,, at 212 Fahr.) better known as boro-tartrate of potash, 

 or tululilt cream of tartar, is obtained on evaporating to dryness one 

 part of boracic acid, two of bitartrate of potash, and twenty-four of 

 water. Tartrate of potash and antimony, sea ANTIMONY. A similar 

 salt containing arsenic (NH 4 0, AsOj, C,H 4 O ]n aq) may be obtained. 



Racemic Acid (2HO,C e H 4 O 10 + 2 aq.) Paratartaric Acid. This 

 isomeric modification is a frequent associate of tartaric acid, but it is 

 in tin: grape of the Upper Rhine that it is abundantly met with. In all 

 its relations it exhibits a close 'analogy to ordinary tartaric acid. The 

 chief points of difference are : that it crystallises more readily from 

 solution : it contains two equivalents of water of crystallisation ; it is 

 less soluble in alcohol ; it gives a precipitate with sulphate of lime, 

 nitrate of lime, and chloride of calcium ; and, finally, the racemate of 

 lime is soluble in hydrochloric acid, and is precipitated unchanged on 

 adding ammonia. By taking advantage of these properties, it may 

 readily be distinguished and separated from tartaric acid. A point of 

 considerable interest, connected with the constitution of racemic acid, 

 is that its solution has no effect on a ray of plane polarised light. 

 The racemates are very like the tartrates : racemate of lime is, how- 

 ever, considerably less soluble, and the double racemate of potash and 

 antimefty crystallises in acicular tufts instead of octohedra. 



Artificial Formation of Racemic Acid. Recently Messrs. Perkin and 

 Duppa, and almost at the name time, Dr. Kekule, have succeeded in 

 producing paratartaric acid. It La formed when bibromosuccinate of 

 silver is boiled in water, bromide of silver being precipitated : 



C 9 H,Br.Ag s 3 + 4HO = SHO, C,n 4 O, + 2AgBr. 



More recently M. Carlet, considering that lactose, which is dextro- 

 rotative, yielded, in the hand of Liebig, ordinary tartaric acid 

 concluded that dulcose (a saccharine principle imported from Mada- 

 gascar) should by similar treatment furnish paratartaric acid. He 

 tried the experiment and succeeded in producing a small quantity of 

 racemic acid. 



Constitution of Tartaric and Paratartaric Acid. By the brilliant 

 researches of M. Pasteur in this direction, chemistry has been put in 

 possession of four kinds of tartaric acid. First, dfxtro-tartaric acid, or 

 that which causes right-handed rotation of a ray of plane polarised 

 light. This is the ordinary tartaric acid met with in commerce ; it in 

 sometimes, and, OH will be seen directly, not inappropriately termed 

 dtxtro-rar.emic acid. Second, kcvo-lartaric acid which produces left- 

 handed rotation, and which is also termed lavo-racemic. The crystals 



of these two acids differ in form in a somewhat interesting manner. 

 Neither of them is ever obtained of a perfectly symmetrical shape, 

 but what is remarkable is that the portion not forthcoming in the one 

 is exactly the reverse of that wanting in the other. Moreover, the 

 salts of the two acids preserve the peculiarities of the acids themselves ; 

 their rotatory power, chemical properties and appearance differing as 

 the acids differ : thus the image, as seen in a mirror, of the crystal 

 which is dextro-hemihedral, as its shape is termed, has the exact form 

 of the fcevo-hemihedral crystal ; while the reflected image of the latter 

 is of course identical with the direct image of the former. The third 

 form of tartaric acid is a combination of the first with the second, aud 

 has, of course, no rotatory power : it is, in fact, racemic or paratartaric 

 acid. 



Racemic acid was, by M. Pasteur, made to yield up its respective con- 

 stituents, dextro- and Uevo-tartaric acid, in the following manner. The 

 double raeemate of soda aud ammonia, made by saturating a quantity 

 of common racemic acid with carbonate of soda, adding a second equal 

 quantity of racemic acid, and finally neutralising by ammonia, was'found 

 to crystallise in opposite hemihedral forms. On picking out, by haud, 

 the one variety from the other and optically examining their solutions, 

 M. Pasteur found that each powerfully twisted a polarised ray, but 

 in opposite directions. From the two salts the acids were isolated 

 by first precipitating with nitrate of lead, then decomposing the 

 washed lead salts by sulphuretted hydrogen, and lastly, allowing 

 crystals to be deposited from the evaporated filtrates. The one set 

 of crystals were found to be dextro-rotatory, the other Isevo-rotatory ; 

 on adding equal quantities together, the original non-rotatory acid was 

 obtained. 



A second process for the separation of dextro-tartaric from loevo- 

 tartaric acid has been discovered by M. Pasteur ; it is not mechanical, 

 like that of the separation from each other of the two kinds of crystals 

 of racemate of soda and ammonia, but chemical, and depends upon 

 principles which are generally applicable. It consists in combining 

 racemic acid, or any other substance suspected of having an analogous 

 binary constitution, with an active gyratory body. The necessary 

 dissimilarity of properties in the compounds which such a body is 

 capable of forming with the constituents of a complete substance will 

 at once reveal whether the suspected body is complex or not. Thus, 

 in preparing the racemate of cinchonicine, it always happens that when 

 the liquid has attained a certain degree of concentration the first crop 

 of crystals formed consists almost wholly of Ucvo-tartrate, the dextro- 

 tartrate remaining in solution. A similar result is obtained with 

 quinicme, except that dextro-tartrate first crystallises out, the laivo- 

 tartrate remaining in the mother liquor. 



The fourth kind of tartaric acid, discovered by the eminent chemist 

 alluded to, is inactive tartaric acid ; it has no action whatever on 

 polarised light and, moreover, is not resolvable, under the same cir- 

 cumstances as is racemic acid, into dextro- and Uevo-tartarie acids. It 

 is formed as follows : tartrate of cinchonine is heated for several hours 

 to 170 Fahr. ; the mass is then treated with water and chloride of 

 calcium added, when racemic acid, formed at the expense of the 

 tartaric acid, is precipitated in the form of racemate of lime. If now 

 the liquid be immediately filtered, and then left at rest for twenty-four 

 hours, an additional crop of crystals is obtained, consisting of pure 

 inactive tartrate of lime ; from the .latter the inactive acid itself is 

 easily prepared. 



A'itrie derivatives of Tartaric Acid. When tartaric acid is dissolved 

 in nitric acid, and sulphuric acid added, a crystalline mass of nitro-tar- 

 taric acid is produced. It is very unstable and difficult to purify. 

 Water decomposes it into tartronic acid (C n H 4 10 ). 



The following derivatives of tartaric acid are prepared by the usua 

 methods : 



Mcthyl-tarturic acid (tartromethylic acid) 

 Tartrate of methyl .... 

 Ethyl-tartaric acid (tartrovinio acid) . 

 Tartrate of ethyl (tartaric ether) . . 

 Amyl-tartaric acid (tartramylic acid) 

 Tartroglyceric acid .... 

 Tartramic acid ..... 

 Tartramide 



C,II,0, HO,C B H 4 O lo 

 2(C 2 'U,0)C,H 4 10 

 . C t H B 0,HO,C,H 4 O lo 

 2(C 4 H 5 0)C.H 4 10 

 CujHuO, HO,C B H,0 10 

 C.H,0., HO, C.H^o 

 C.H 7 N0 10 

 C.H.N.O,, 



Tartaric acid is much used in medicine; extensively also in the 

 preparation of effervescing drinks, and, by the calico-printer and 

 dyer. 



TARTARIC ACID, for medical purposes, should be remarkably 

 pure, when it is without odour, but makes a powerful acid impression 

 on the organs of taste. In small doses, properly diluted, it acts as a 

 refrigerant, and is of much value in fevers, particularly mucous, and 

 in biliary remittents. It excites the appetite of persons in whom the 

 stomach is in a healthy condition ; and those who, by long indulgence 

 in .stimulating food and drinks, experience loss of appetite, painful 

 digestion, constipation, with a yellow and altered countenance, and 

 diminished muscular vigour, find in tartaric acid a remedy of sin- 

 gular power. For this state of system a few crystals should be 

 dissolved in two small tumblers, and drank in the morning fasting, 

 an hour intervening between the tumblers. A few grains are suffi- 

 cient for each tumbler, as when made too strong it excites irrita- 

 tion, followed by purging. Occasionally it disturbs the nervous system 



