304

ELEMENTS OF MATERIA MEDICA.

tion than the tartrate of soda. The citrate promotes slightly the secretionsof the alimentary canal, the cutaneous transpiration, and the renal secre-tion : and like other vegetable salts of potash, renders the urine alkaline.

Administration. —This salt may be given in doses of from gr. x. togr. xv. or to the extent of half a drachm, or even a drachm.

Liquor Potassje Efferfescf.ns (Ph.L.)—The effervescing solutionof (bicarbonate of) potash is ordered to be prepared by dissolving a drachmof bicarbonate of potash in a pint of water, and passing into the solutioncarbonic acid compressed by force, more than sufficient for saturation.The solution is to be kept in a well-stopped vessel. This preparationhas been introduced as an agreeable form for exhibiting carbonate ofpotash, without diminishing its constitutional operation.

Potas'sce Ace'tas. — Ac'etate of Pot'ash .

History. —It appears to have been first clearly described by RaymondLully in the thirteenth century, and has been known by several appella-tions, such as terra foliata tartari, diuretic salt, &c.

Natural History. —Geiger ( Handbuch der Pharmacie ) says this saltis found in some mineral springs. It probably exists in most plantswhich, by incineration, yield carbonate of potash. The sap of the elmand of most trees, Winter’s bark, linseed, senna leaves, the rhizome ofginger, &c. are said to contain it.

Preparation. —It is prepared by adding a pound of carbonate ofpotash to twenty-six fluidounces of acetic acid (Ph. L.) mixed withtwelve fluidounces of distilled water, or sufficient acid to saturate thecarbonate. Evaporate the strained liquor in a sand-bath, the heat beingcautiously applied until the salt is dried.

In this process the acid unites with the potash of the carbonate, anddisengages carbonic acid.

Properties. —It is usually met with as a colourless, white solid, witha foliated texture (which is given to it by fusion and cooling), odourless, buthaving a pungent saline taste, and a soapy feel. It is exceedingly deli-quescent, and, therefore, ought to be preserved in a well-stopped bottle. Itis very soluble both in water and alcohol; indeed, in water, it is one of themost soluble salts we are acquainted with. At 60°, 100 parts of the saltwill dissolve in 102 parts of water. When heated, it fuses and is decom-posed into pyroacetic spirit, and carbonate of potash. One equivalent ofthis spirit contains the elements of one equivalent of acetic acid, minusthose of one equivalent of carbonic acid.

Characteristics. —(See the tests for the acetates, p. 222, and forpotash, p.274).

Composition. —Its composition is as follows :—

Eq. Eq.Wt. PerCent. Wenzel.

Potash. 1 .... 48 ... . 48-5 .... 50*15

Acetic Acid (dry) .... 1 .... 51 ... ■ 51*5 .... 49*85

Acetate of Potash ... 1 .... 99 ... . lOO'O .... 100*00

Purity. —It should be white and perfectly neutral. Frequently,however, it reacts as an alkali, owing to a slight excess of potash. Thepresence of chlorides may be detected by nitrate of silver; of sulphates,by chloride of barium; of metals, by hydrosulphuric acid or ferrocyanideof potassium.