Preparation

Tartaric acid exists, in the free state, in several vegetable juices, among which are those of grapes, tamarinds, and pine-apples. For use, it is obtained from bitartrate of potassa, by first saturating the excess of tartaric acid in that salt by means of carbonate of lime, and then decomposing, by sulphuric acid, the insoluble tartrate of lime produced; water, of course, being employed in the process, to facilitate the reactions. in the last step of the process, insoluble sulphate of lime is formed, and the liberated tartaric acid remains in solution, from which it is separated by concentration and crystallization.

Properties

The crystals are irregular six-sided prisms, sometimes flattened into a tabular form, whitish, translucent, permanent in the air, inodorous, and of a very sour taste, which is agreeable when they are in weak solution. As usually kept in the shops, the acid is in the state of a white powder. it is very soluble in water, and is soluble also in alcohol. The aqueous solution undergoes decomposition when kept. The anhydrous acid consists of 4 equivalents of carbon, 2 of hydrogen, and 5 of oxygen; which, in the crystalline form, are united with 1 eq. of water. if, however, the acid be considered, with many chemists, as bibasic, these numbers must be doubled.

This acid may be recognized by forming, with a strong solution of carbonate of potassa, a copious precipitate of the bitartrate.

Effects on the System

These are the same as those of the sour vegetable acids in general. The acid is locally excitant, or, in a concentrated state, irritant; and, upon the system at large, acts as an arterial sedative, with a disposition to promote the urinary secretion, and sometimes to act as a laxative.

Dr. Christison states, in his treatise on poisons, that he had given a drachm to cats without any observable inconvenience; and mentions an instance, on the authority of a surgeon of his acquaintance, in which six drachms were taken during twenty-four hours, without producing any troublesome effects. Mitscherlich, however, killed a rabbit in an hour with three or four drachms; and, when less than sufficient to cause death was given, the symptoms were those of depression and paralysis. Dr. Taylor, in his work on poisons, gives the details of a case, in which a man, having swallowed an ounce of the acid, dissolved in half a pint of water, complained immediately of a burning pain in his throat and stomach, and was attacked with vomiting, which continued until his death, nine days after it was taken. Almost the whole of the alimentary canal was found inflamed. The acid must, therefore, be considered as an irritant poison in very large doses. The treatment of its poisonous effects is the same as in the case of poisoning by acetic acid.

Therapeutic Application

Dissolved in water and sweetened, tartaric acid may be used as a cheap substitute for lemonade in febrile affections; but it is less agreeable, and more apt to irritate the stomach. it is chiefly employed in the preparation of effervescing laxative and refrigerant powders. For an account of the Seidlitz powders, in which it forms an ingredient, the reader is referred to the article upon the tartrate of potassa and soda, or Rochelle salt. The common soda powders, as usually prepared, consist of 25 grains of powdered tartaric acid in one paper, and 30 grains of bicarbonate of soda in another. When used, the powders are dissolved in separate portions of water, and the two solutions then mixed. Carbonic acid escapes with effervescence, and tartrate of soda remains in solution. The quantity of water employed may be from four to eight fluidounces. The preparation is taken while effervescing, and the dose may be given every two or three hours in febrile affections. it operates gratefully as a refrigerant, and often as a gentle laxative, and is much used. The same ingredients, previously well dried, may be mixed in larger quantities, but in the same proportion, and kept in well-stopped glass bottles. A teaspoonful of the mixture, thrown into a gill of water, will form an effervescing solution, as in the former method. in either case, simple syrup, or the syrup of orange-peel, may be added to the liquid used. About fifteen grains of the acid, dissolved in a tumbler of sweetened water, produces an agreeably sour solution, which may be used for a drink in fevers.