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ELEMENTS OF MATERIA MEDICA.

Observations, part i. p. 82), a patient swallowed soap lees: this producedinflammation, which terminated in stricture. She lingered for 20 years,and died literally starved. Several other cases have been detailed.(Christison, On Poisons.) A weak solution of carbonate of potash pro-duces no change in the sanguineous particles drawn from the body: asaturated solution slightly and gradually diminishes their size.

Uses. —This salt is employed in medicine in most of the cases alreadymentioned when describing the uses of caustic potash. For example, asan antacid in dyspeptic affections; as a diuretic; as an antacid in thatform of lithiasis which is accompanied with an increased secretion oflithic acid, or the lithates ; in those forms of inflammation in which thereis a tendency to the formation of false membranes ; in gout, &c. Mixedwith cochineal it is a popular remedy for hooping-cough. Externally, ithas been applied in the form of a solution to wounds ; as an injection ingonorrhoea; as a collyrium in some affections of the cornea, &c. Lastly,it is sometimes employed in the manufacture of the common effervescingdraught, made with either the citric or tartaric acid. Twenty grains ofcarbonate of potash are saturated by about 17 grains of the citric acidof commerce, by 18 grains of tartaric acid, or by siv. of lemon juice.

Administration. —It may be given either in the solid or liquid state.In the solid state it is given in doses of from gr. x. to 5ss. The doses ofthe liquor potasses carbonatis of the Pharmacopoeia is from ten minims toa fluidrachm.

Antidotes. —When swallowed as a poison, the antidotes are oils oracids, as already mentioned ior the caustic potash.

Potas'see Bicar'bonas. — Bicar'bonate of Pot'ash .

History. —This salt, formerly called carbonate of potash or aeratedkali, was first prepared by Cartheuser in 1752.

Preparation, (a.) Process of the Pharmacopoeia . —In the LondonPharmacopoeia we are directed to pass carbonic acid (generated by theaction of equal weights of sulphuric acid and water in powdered chalk),through a solution of six pounds of the carbonate in a gallon of distilledwater, to saturation. Apply a gentle heat, so that whatever crystals haveformed may be again dissolved. Then set the solution aside that crys-tals may be formed, which are to be dried.

In this process, each equivalent of carbonate of potash unites with anadditional equivalent of carbonic acid, and thereby forms the bicarbonate.The silicic acid is separated partly w'hile the carbonic acid is passingthrough the solution, and partly during the crystallization of thebicarbonate.

(b.) Cartheuser's Process. —In the Pharmacopee Raisonnee of MM.Henry and Guibourt the following directions are given for performingthis process:—Dissolve 500 parts of (pure) carbonate of potash in 1000parts of distilled water, and filter: place the solution in a porcelain cap-sule in a salt-w r ater bath, and gradually add 300 parts of pulverizedcarbonate of ammonia: slightly agitate the liquor until only a feeble dis-engagement of ammonia is perceived, then filter over a heated vessel,and put aside to cool. The proportions employed by Geiger ( Handbuch.d. Pharm.) are somewhat different: they are, a pound of carbonate ofpotash, sixteen ounces of water, and six ounces of carbonate of ammonia.Mr. Brande ( Manual of Chemistry) says Cartheuser’s process is moreexpensive than that of the Pharmacopoeia .