Tartaric acid

“ Absence of rotary power when asymmetric carbon atoms are present, may be caused by an internal compensation within the molecule as with the inactive tartaric acid (meso-tartaric acid) , or may be due to the fact that the compound is an equimolecular mixture of left- and right-hand varieties, this being the case with racemic acid that was broken by Louis Pasteur into laevo- and dextro-tartaric acid (see Stereo-Isomerism) . ”

“ Tartaric acid. (a) An acid widely diffused throughout the vegetable kingdom, as in grapes, mountain-ash berries, etc., and obtained from tartar as a white crystalline substance, C2H2 (OH) 2. (CO2H) 2, having a strong pure acid taste. It is used in medicine, in dyeing, calico printing, photography, etc., and also as a substitute for lemon juice. Called also dextro-tartaric acid. (b) By extension, any one of the series of isomeric acids (racemic acid, levotartaric acid, inactive tartaric acid) of which tartaric acid proper is the type. ”

“ The double tartrate of potash and soda was first prepared in 1672 by Peter Seignette, an apothecary of Rochelle, and was used by him in medicine. Tartar emetic was discovered by Adrian158 von Mynsicht in 1631, and its true nature explained by Bergmann in 1773. Racemic acid was first mentioned by a wine manufacturer named Kestner, and was recognised as an acid in 1819. Its relation to tartaric acid, with which it is isomeric, was first explained by Berzelius, who gave it its name. ”

“ Nay, an obvious mode of correcting excessive acidity, produced by too much tartaric acid, is to add tartaric acid, and then to treat the mixture with oxide of lead. Fourcroy farther thinks, that the malic acid possesses the same solvent power as the acetic over tartrate of lead, and that its presence may therefore be the reason why some tart wines, which do not contain the acetic acid, become nevertheless impregnated with the poison. The solvent power of acetic acid is increased by the 422presence of other vegetable principles in the wine. ”

“ Dextro-tartaric acid occurs in the free state or as the potassium or calcium salt in grape juice and in various unripe fruits. During the alcoholic fermentation of grape juice it is deposited in the form of an impure acid potassium tartrate which is known as arg&l, and when purified as cream of tartar. For the preparation of the acid the crude argol is boiled with hydrochloric acid and afterwards precipitated as calcium tartrate by boiling with milk of lime, the calcium salt being afterwards decomposed by sulphuric acid. ”

“ In a saturated solution of tartaric acid dissolve freshly precipitated ferric oxide, and keep the solution—ferric tartrate—in the dark. To prepare the sensitizing solution, dissolve 20 parts of uranic nitrate and from 1 to 3 parts of tartaric acid in 100 parts of water, and add a small quantity of ferric tartrate, the proportion varying with the tint desired: an excess gives a blue black. With this solution brush the [pg 46] paper over, and, when dry, expose under the negative cliché, then develop with a solution of potassium ferricyanate at 4 per 100 of water. ”

“ The optically inactive form of tartaric acid, known as racemic acid, has been obtained by M. Gensesse as an eventual product of the action on glyoxalic acid—an acid found in gooseberries, grapes, and other fruits—with nascent hydrogen liberated from a mixture of zinc-dust and acetic acid. ”

“ This part of the process is often performed by mere digestion for a few days, without the application of heat. Leaden or stoneware vessels are used as crystallisers. Good cream of tartar requires 26% of chalk and 28·5% of dry chloride of calcium for its perfect decomposition. Dry tartrate of lime requires 75% of oil of vitriol to liberate the whole of its tartaric acid. A very slight excess of sulphuric acid may be safely, nay, advantageously, employed. Some manufacturers bleach the coloured solution of the first crystals by treating it with animal charcoal ”

“ Tartrate of potass is discovered by adding a solution of tartaric acid, which will occasion with it a copious precipitate; the sulphates, by their forming with acetate of lead, or muriate of baryta, precipitates insoluble in acetic or muriatic acid. The brown tinge which it frequently exhibits depends upon the same cause as that which usually imparts colour to the Liquor. Ammon. Acet. This salt is also sometimes contaminated with lead, which arises from its having been prepared by decomposing the acetate of lead by means of carbonate of potass. ”

“ TARTARIC ACID, in its ordinary acceptation, refers to one acid, (C4H4O6) H2, which occurs in most acid fruit juices, in association generally with malic or citric, or both. Grape-juice owes its sourness almost entirely to acid tartrate of potash. While the juice ferments into wine, the greater part of the acid tartrate separates out, along with tartrate of lime, colouring matter, and other impurities, as a hard crust adhering to the sides of the cask. Such impure acid tartrate of potash is known commercially as "argol." ”

“ The tartrate of lead is very sparingly soluble in an excess of its acid, so that a sweet taste cannot be communicated by it to a fluid acidulated with tartaric acid. Malic acid, according to MM. Chevallier and Ollivier, acts so quickly as a solvent, that if a solution be kept in a lead vessel for three hours, the metal may be detected in the fluid by any of its ordinary tests. [1260]
The acids act with greater rapidity on the protoxide of lead than on the metal; and the presence of air is of course not required to enable them to effect its solution. ”

“ Sulphuretted hydrogen, sulphide of ammonium, and carbonate of ammonium, do not affect them. A solution of tartaric acid, added in excess, to moderately strong neutral or alkaline solutions of potassium salts, gives a quickly subsiding, gritty or crystalline, white precipitate, which is redissolved on heating the liquid, and again separates as it cools; and is also soluble in aqueous solutions containing free alkali, or free mineral acids. Platinic chloride produces, in neutral and acid solutions, a yellow crystalline precipitate. ”

“ The method called “spontaneous separation” was first observed by Pasteur with racemic acid, which in its double sodium and am- monium salt crystallized from its aqueous solution in two enantio- morphic forms, which could be separated on examination. One of the two proved to be the ordinary sodium-ammonium-tartrate, the other its laevogyre antipode; thus /-tartaric acid wasdiscovered, and racemic acid proved to be a combination of d- and /-tartaric acid. ”

“ He discovered that whenever chromate of potash has its acid set free by its being mixed with tartaric or oxalic acid, or a neutral vegetable substance, (starch or sugar for example) , and a mineral acid, a very lively action is produced, with disengagement of heat, and of several gases. The result of this decomposition is the active reagent, chromic acid, possessing valuable properties to the printer. Watery solutions of chromate of potash and tartaric acid being mixed, an effervescence is produced which has the power of destroying vegetable colours. ”

“ In every state it is deliquescent and very caustic. It cannot be crystallized. It gives out carbonic acid gas with the addition of any stronger acid, such as sulphuric, muriatic, or acetic acid. Its solution precipitates yellow with the chloride of platinum, gives a crystalline precipitate with perchloric acid, when the salt forms not less than a fortieth or fiftieth part,—is similarly acted on by a considerable excess of tartaric acid, if the salt constitute about a thirtieth of the fluid,—and yields with the soluble salts of baryta a white precipitate soluble in nitric acid. ”

“ Oxalic acid (but not tartaric acid) in minute quantities destroys the colour. Nitrous acid strikes a red colour with the sulphocyanate of potassium; consequently, when nitric acid has been used in excess, high results may be obtained. Copper and some other metals interfere, so that in most cases it is advisable to concentrate the iron before estimating it. A blank experiment should always be made with the reagents used in order to determine the iron, if any, introduced during the solution, &c., of the substance assayed. ”

“ Tartaric acid is such a substance; and if a single spore of the commonest and most troublesome of moulds—Penicillium—be sown in a saucerful of water, in which tartrate of ammonia, with a small percentage of phosphates and sulphates is contained, and kept warm, whether in the dark or exposed to light, it will, in a short time, give rise to a thick crust of mould, which contains many million times the weight of the original spore, in protein compounds and cellulose. ”

“ These materials tend to keep apart the particles of acid and base and render it possible to make a mixture of them which may be kept for a long while without any notable loss of leavening power. When a cream of tartar baking powder is mixed with dough the moisture of the dough gradually dissolves the two ingredients and in this state a chemical reaction occurs between them. The carbon dioxid is set free as a gas, commonly known as carbonic acid. The mineral substance which results is a tartrate of sodium and potassium that is a union of tartaric acid with potash and soda. ”

“ It is better not to mix too much at a time, as it is apt to get damp. About four teaspoonsful of soda and two of acid is a convenient quantity, and to about a pound of flour use one teaspoonful of powder. Many cooks prefer cream of tartar to the stronger acid: possibly one is as good as the other, but the tartaric acid being stronger I prefer it. In mixing the baking powder into anything, it should always be rubbed in with the dry flour; if put in when the mixture is moist it effervesces at once, so half or three parts of its effect is lost before the cake is ready. ”

“ Common grades of the salt contain a little sodium chloride, and in some cases as much as 2 per cent. of the corresponding sulphate; it may also prove to be somewhat deficient in the proportion of carbonic acid present. Cream of tartar (potassium bitartrate) , is far more liable to adulteration. A certain quantity of calcium tartrate is often found in the commercial article, originating from its method of manufacture, and amounting, on the average, from 6 to 7 per cent. The salt is, moreover, sometimes intentionally mixed with alum, starch, tartaric acid, gypsum, chalk and terra alba. ”

“ It is entirely soluble in both water and alcohol. Its aqueous solution alters the colour of turmeric either not at all or but very slightly, nor does it affect litmus paper, or effervesce with acids. Nitric acid and starch being added together, it becomes blue. It is not coloured by the addition of tartaric acid with starch. No precipitate occurs on adding either a solution of hydrate of calcium or of chloride of barium. 100 gr., dissolved in water, by the addition of nitrate of silver, yield a precipitate of 141 gr. ”

“ This may be shown by heating some cream of tartar or tartaric acid on a strip of metal or glass. It will become carbonized to a cinder, like other organic matter. If the heat is raised sufficiently, this cinder will all burn away to carbonic acid and water in the case of the pure acid, or will leave carbonate of potash in the case of cream of tartar or other potash salt. ”

“ Other Acids used.—When hydrochloric acid is used, instead of tartaric acid, or cream of tartar, it combines with the soda to form chloride of sodium, better known as common salt. It is more difficult to mix than the dry acid, but it has the advantage that common salt is always harmless, while tartrate of soda is an aperient, having exceptional action upon a few constitutions. There are persons who cannot eat bread made with baking-powder ”

“ So far as his investigations showed, all crystals of tartaric acid had hemihedral faces; but he had found none on the racemates. Conceiving that this aspect of crystals might be an index of their molecular structure, he reasoned that the diverse optical behaviors of solutions of tartaric and racemic acids might be explained by a structural law. On fire with this new idea, he carefully examined a lot of tartrate crystals, and found, as he had anticipated, that each had hemi-hedral facets. He turned now to racemate crystals, expecting to find them destitute of hemihedrism. ”

“ Hence, the only conclusion possible is that racemic acid must be a molecular compound of the two oppositely optically active tartaric acids. It thus partakes of the character of a double salt, analogous to potassium magnesium sulphate for instance. Consequently the crystal structure is one in which alternating molecules of the two acids are uniformly distributed, and the case is actually presented of two oppositely enantiomorphous sets of molecules producing a homogeneous structure. ”

“ Ammonium carbonate has been used to some extent, but is very seldom used at the present time. The acid constituent may be one of several materials, the most common being cream of tartar, tartaric acid, calcium phosphate, or alum. These may be used separately or in combination. The various baking powders are designated according to the acid constituent, as "cream of tartar," "phosphate," and "alum" powders. All of them liberate carbon dioxid gas, but the products left in the food differ widely in nature and amount [69] . ”