Acidum Tartaricum (U. S. P.)—Tartaric Acid.
FORMULA: H2C4H4O6. MOLECULAR WEIGHT: 149.64.
SYNONYMS: Dextro-tartaric acid, Dioxysuccinic acid, Sal essentiali tartari.
"An organic acid usually prepared from argols"—(U. S. P.).
Source and History.—Scheele first prepared this acid in 1769. Retzius, in 1770, produced it in crystalline condition. Tartaric acid is a constituent of grape juice in the form of an acid tartrate of potassium, and is also contained in many other plants, as in the juice of the pineapple, tamarind, sorrel, mulberry, "sumach-bob," etc. The acid of commerce is produced almost exclusively from "crude tartar" or "argols," a refuse by-product in the manufacture of wines. Formerly the American market was chiefly supplied by European manufacturers, but at the present time nearly all of the acid consumed here is produced in the United States from argots shipped from European ports.
Preparation.—This acid is prepared somewhat similarly to citric acid, by forming tartrate of calcium and decomposing it by sulphuric acid; this is generally effected by adding an excess of carbonate of calcium to a solution of acid tartrate of potassium, which yields a precipitate of insoluble tartrate of calcium. The remaining salt in solution (neutral potassium tartrate), is then treated with calcium chloride, which decomposes it with the production of soluble potassium chloride and insoluble calcium tartrate, which latter product is then collected, thoroughly washed, and acted upon by sulphuric acid, which sets the tartaric acid free, and forms a precipitate of sulphate of calcium. To obtain the acid pure, it is evaporated, crystallized, redissolved in water, strained, and recrystallized three or four times. When prepared on an extensive scale, sulphate of calcium is substituted for chloride of calcium on account of the cheapness of the former. The colored crystals are treated with charcoal and recrystallized. The finest crystals are produced when there is a slight excess of sulphuric acid.
Description.—Tartaric acid occurs in "colorless, translucent, monoclinic prisms, or crystalline crusts, or a white powder, odorless, having a purely acid taste, and permanent in the air. Soluble at 15° C. (59° F.), in about 0.8 part of water, and in 2.5 parts of alcohol; in about 0.5 part of boiling water, and in about 0.2 part of boiling alcohol; also in 250 parts of ether; nearly insoluble in chloroform, benzol, or benzin. When heated for some time at 100° C. (212° F.), the powdered crystals do not suffer a sensible loss of weight. At 135° C. (275° F.), the acid melts. At higher temperatures it is gradually decomposed, emitting the odor of burning sugar, and is finally consumed without leaving more than 0.05 per cent of ash. Tartaric acid has an acid reaction upon litmus paper"—(U. S. P.).
Its aqueous solution molds on exposure, yielding acetic and butyracetic acids. Fused with hydroxide of potassium, it decomposes into acetic and oxalic acids and water. When gently heated, the crystals of tartaric acid acquire electrical polarity equal to that of tourmaline. Tartaric acid possesses in a remarkable degree the property of turning the plane of polarized light to the right, which is increased by warming the substance, as well as by combination with bases. Nitric acid immediately decomposes it into oxalic and carbonic acids; chlorine does not decompose it. Tartaric acid gives rise to tartrates of two kinds, the neutral and acid tartrates; with caustic potash and ammonia it forms neutral salts, easily soluble, and acid salts not easily soluble. When heated with sulphuric acid they are readily charred. Tartaric acid may be reduced to succinic acid by saturating its concentrated aqueous solution with, hydriodic acid, sealing in a strong glass tube, and heating it for 6 or 8 hours, not to exceed the temperature of 120° C. (248° F.). Tartaric acid may be known by its sour solution, which gives white precipitates with solutions of caustic lime, baryta, strontia, and acetate of lead, the precipitated tartrates being soluble in excess of acid. Ammonium chloride dissolves the precipitate produced by lime-water. Sulphate of calcium gives no precipitate; a solution of chloride of platinum causes a black precipitate of metallic platinum. Most of the commercial tartaric acid is in the form of a white, crystalline powder.
By the researches of M. Pasteur, the existence of four isomers of tartaric acid (dextro-tartaric) was established, all having the same formula, H2C4H4O6, but differing principally in their behavior towards polarized light. These isomers are: (1) racemic, (2) laevo-tartaric, (3) meso-tartaric, and (4) meta-tartaric acids.
Other tomes: AJP1871
1. Racemic acid (para-tartaric or uvic acid), occurs in the mother liquors obtained in the making of cream of tartar. It is optically inactive, being a compound of equal amounts of dextro- and laevo-tartaric acids, and has been resolved into its constituents by preparing a supersaturated solution of its sodium-ammonium salt and dropping into the fluid a crystal of the sodium-ammonium salt of either the dextro- or the laevo-rotatory acid, whereby this form of salt will crystallize out while the other form remains in solution. Mineral acids will then liberate the respective free tartaric acids from these salts. Racemic acid is best obtained by heating ordinary tartaric acid with 0.1 part of water, to 175° C. (347° F.), whereby it is completely converted into meso-tartaric and racemic acids. It crystallizes more readily than tartaric acid, into efflorescent, triclinic prisms, containing 1 molecule of water of crystallization. Its acid potassium salt is by far more soluble than the salt of dextro-tartaric acid (cream of tartar); its calcium salt is distinguished by its being insoluble in acetic acid.
2. Laevo-tartaric acid, turns the plane of polarized light to the left, and has otherwise the general properties of the dextro-acid.
3. Meso-tartaric acid, is formed when dextro-tartaric acid is heated to 165° C. (329° F.), with about one-eighth its quantity of water, for about 2 hours. It is optically inactive and can not be resolved into dextro- and laevo-tartaric acids.
4. Meta-tartaric acid, is formed when dextro-tartaric acid is heated till it fuses, i.e., to 130° C. (266° F.). It is also dextro-rotatory, but differs from ordinary tartaric acid mainly in its deliquescence and that of its salts.
Tests.—The U. S. P. directs the following tests for tartaric acid: "An aqueous solution (1 in 2) of the acid mixed with a strong solution (1 in 3) of potassium acetate yields a white, crystalline precipitate which is soluble in solutions of alkalies and in mineral acid, but insoluble in acetic acid. The aqueous solution (1 in 10) of the acid, acidulated with a few drops of hydrochloric acid, should remain unaffected by barium chloride T.S. (absence of sulphuric acid). Another portion of the aqueous solution (1 in 10) in which the free acid has been nearly, but not entirely, neutralized by ammonia, should not be affected by calcium sulphate T.S. (absence of and difference from oxalic and uvic acids). On supersaturating 10 Cc. of the aqueous solution (1 in 10) with ammonia water, no turbidity should be produced in the liquid by ammonium oxalate T.S. (absence of calcium), nor should the further addition of 1 drop of ammonium sulphide T.S. produce any dark coloration or precipitate (absence of iron, lead, copper, etc.). To neutralize 3.75 Gm. of tartaric acid should require 50 Cc. of potassium hydrate V.S. (each Cc. corresponding to 2 per cent of the pure acid), phenolphtalein being used as indicator"—(U. S. P.).
Action, Medical Uses, and Dosage.—Tartaric acid in large doses is an unsafe agent, causing gastro-intestinal inflammation and death. The symptoms in man from 1 ounce largely diluted, were intense, burning pain in the fauces and stomach, persistent vomiting, and death in nine days, the effects being those of a corrosive poison.
Tartaric acid is refrigerant, antiseptic, and antiscorbutic. It is used as a drink in febrile or inflammatory diseases, forming a cooling, refreshing, and agreeable acidulous draught. It is less costly than citric acid, and may be used instead of this acid to form an artificial lemonade. Tartaric acid enters into the composition of Seidlitz, as well as of soda powders. A colorless solution of sulphate of quinine has long been employed by physicians; it may be made by adding equal arts of tartaric acid and sulphate of quinine to as much water as may be desired. The dose of tartaric acid is from 10 to 30 grains dissolved in water or syrup.
Related Preparation.—ACIDUM TARTARICUM SACCHARATUM (N. F.), Saccharated tartaric acid. Formulary number, 8: "Tartaric acid (U. S. P.), in very fine powder, six hundred and seventy-five grammes (675 Gm.) [1 lb. av., 7 ozs., 354 grs.]; sugar, in very fine powder, three hundred and twenty-five grammes (325 Gm.) [11 ozs. av., 203 grs.]. Triturate the powders together until intimately mixed, and preserve the product in well-stoppered bottles.
"Note.—This saccharate, when dissolved in water with an equal weight of saccharated sodium bicarbonate (F. 341). will form a neutral solution, and it is introduced into the formulary for the convenient preparation of effervescent powders (F. 319). This saccharate contains 67.5 per cent of tartaric acid"—(.Nat. Form.).