Ki = 39.1.
Potassium (L. for potash - pot + ash - i. e., origin of the salts by evaporating wood-ash lye in pots; Ar. kali, L. kalium, ashes) occurs in nature to a great extent as a double silicate of potassium and aluminum (granitic rocks, feldspar, etc.), also as chloride, nitrate, bitartrate, and carbonate, the latter being the predominant salt in wood-ashes. The metal is obtained by heating this carbonate with carbon in iron retorts, passing the evolved vapors into coal-oil in order to condense the metal - K2CO3 + 2C = 2K + 3CO. Plants derive much of their potassium from these disintegrated rocks, containing the silicate, which is absorbed by falling rain; this percolates through the soil, and from that the plant-roots (rootlets, trichomes) in turn take it. Potassium occurs also in native wood, chiefly as the acetate, but to some extent as sulphate, chloride, tartrate, citrate, etc., most of which upon incineration become converted into the carbonate.
Tests for Potassium Salts: 1. With platinic chloride, alcohol, and HC1, get a yellow crystalline precipitate (PtCl42KCl). 2. With strong solution of tartaric acid, get a white crystalline precipitate of cream of tartar - alcohol facilitates the precipitation. 3. The flame of a Bunsen burner is colored violet, which can be recognized, even though sodium be present, through the intervention of blue glass or indigo solution. 4. Potassium salts are soluble in water, non-volatile, and usually white.
Potassii Carbonas. Potassium Carbonate, K2CO3. - (Syn., Pot. Carb., Salt of Tartar, Carbonas Potassicus (Kalicus), Potassii Carbonas Purus, Sal Tartari; Fr. Carbonate de Potasse; Ger. Kalium carbonicum, Kaliumcarbonat, Kohlensaures Kali.)
Manufacture: This is obtained by percolating wood-ashes with water, which takes up the potassium carbonate together with a little chloride, sulphate, also the sodium salts, while calcium and magnesium carbonates, phosphates, and sulphates, together with silica, are left behind. This percolate (lye) is evaporated, giving crude potash (Kalium carbonicum crudum, Pottasche, Ger.), which by calcining becomes pearl-ash, and this in turn purified yields the official carbonate. It may also be derived from residual ash in beet-sugar manufacture, or washings of sheep-wool, or from the native chloride by Leblanc's process for sodium carbonate, and likewise from the purer bicarbonate by heat - 2KHCO3 = K2CO3 + H2O + CO2. It is a white granular powder, odorless, strongly alkaline taste, very deliquescent, soluble in water (.9), boiling water (.7), insoluble in alcohol, aqueous solution (1 in 20) strongly alkaline to litmus and phenolphthalein T. S., effervesces with acids; contains, when dried, 99 p. c. of pure salt, but may have 15 p. c. of moisture. Tests: 1. Heat to 180° C. (356° F.) - loses all water; at bright red heat - melts; at white heat - volitilizes, imparting violet flame with a possible transient yellow tinge. 2. Aqueous solution
(1 in 10) with excess of tartaric acid T. S, - white crystalline precipitate of potassium bitartrate. Impurities: Heavy metals, earthy substances. Should be kept in air-tight containers. Dose, gr. 10-30 (.6-2 Gm.); externally in solution (2 p. c. + water), ointment (2-12 p. c. + lard).
Preparations. - 1. Pilulae Ferri Carbonatis, 1 1/4 gr. (.075 Gm.). 2. Syrupus Rhei, 1 p. c. 3. Syrup us Rhei Aromaticus, .1 p. c.
Unoff. Prep.: Liquor Potassae Chlorinaae - dissolve potassium carbonate 58 Gm. in boiling water 300 Ml. (Cc), add it to chlorinated lime 80 Gm. mixed with water 400 Ml. (Cc), shake, cool, add water q. s. 1000.
Uses. - Chiefly in the preparation of the other potassium salts, also as an antacid in dyspepsia, diuretic in dropsy, antilithic in uric acid gravel, jaundice; externally in cutaneous affections, caustic, irritant poison.
Poisoning: Same as for potassium hydroxide. Give antidotes - fixed oils, vegetable acids, lemon juice, vinegar, demulcents.
Potassii Bicarbonas. Potassium Bicarbonate, KHCO3. - (Syn., Pot. Bicarb., Acid Carbonate of Potassium, Kali Carbonicum Acidulum, Bicarbonas Potassicus (Kalicus); Fr. Bicarbonate de Potasse; Ger.
Kaliumbicarbonicum, Kaliumbicarbonat, Doppelt-Kohlensaures Kali.) Manufacture: Pass carbon dioxide through strong solution of potassium carbonate, when the less soluble bicarbonate precipitates - K2CO3 + H2O + CO2 = 2KHCO3. It is in colorless, transparent, monoclinic, odorless prisms, or white, granular powder, saline, slightly alkaline taste, permanent, soluble in water (2.8), hot water (2), almost insoluble in alcohol; contains 99 p. c. of pure salt. Tests: 1. Aqueous solution (1 in 10) slightly alkaline to litmus, neutral or slightly alkaline to phenolphthalein T. S.; effervesces with acids; heated above 50° C.
(122° F.) rapidly loses carbon dioxide and water, and at boiling salt is converted into normal carbonate. 2. Heated to 100° C. (212° F.) salt loses carbon dioxide and water, and at red heat yields residue of carbonate, which gives violet flame; aqueous solution with excess of tartaric acid T. S. - white, crystalline precipitate of potassium bitartrate. Impurities: Heavy metals, carbonate, etc. Should be kept in well-closed containers. Dose, gr. 5-60 (.3-4 Gm.), well diluted. Preparations. - 1. Liquor Potassii Arsenitis, 2 p. c. (+ arsenous acid 1 p. a). 2. Liquor Potassii Citratis, 8 p. c. of bicarbonate. 3. Liquor Magnesii Citratis. 38.5 gr. (2.5 Gm.) of bicarbonate to each bottle. Uses. - As the purest source of the potassium salts, similar to carbonate, but has milder taste and is more acceptable to the stomach. Used in beverages, laxative draughts, etc.
Potassii Hydroxidum. Potassium Hydroxide, KOH. - (Syn., Pot. Hydrox., Caustic Potash, Potassium Hydrate, Potassa, Kali Hydricum Fusum (Purum), Oxydum Potassicum, Lapis Causticus Chirurgorum; Br. Potassa Caustica; Fr. Potasse caustique (fondue), Pierre a Cautere; Ger. Kali causticum fusum, Kaliumhydroxyd, Atzkali.)