Potassium

POTASSIUM (Kalium, s. Potassium), a chemical element, symbol K, atomic number 19, a silvery-white, shiny metal having the density of wax at ordinary temperature; discovered by Davy in 1807. Specific gravity at 20° is 0.8621, atomic weight 39.1, monovalent; melting point 62.5°; at 757.5° it turns into green-colored vapors. The colorless flame of a Bunsen burner is colored violet by potassium and its compounds; in spectroscopy, such a flame gives two red and one violet line (resp. corresponding dark lines in the absorption spectrum). Potassium was obtained by heating a dried mixture of potassium carbonate and coal in an iron retort (K₂CO₃+2C=2K+3CO). The modern, more frequent method of obtaining potassium is the electrolysis of molten caustic, chloride, or cyanide of potassium (requires special caution, as molten potassium easily self-ignites in air). Metallic potassium (like sodium) enters into chemical reactions extremely easily. Thrown into water, it energetically decomposes it even at ordinary temperature (2K+2H₂O->2KOH+H₂+88.2 large calories); the hydrogen released from the heat generated ignites, and the flame is colored violet by the potassium vapors; metallic potassium forms NH₂K with gaseous ammonia; it ignites in chlorine and bromine (yielding KBr, KCl); upon heating, it removes oxygen from CO and releases carbon; with hydrogen, it forms KH in the form of white crystals soluble in liquid ammonia; in moist air, these crystals explode. With metalloids, potassium gives easily soluble salts. In nature, potassium is found in the earth's crust in the form of stony siliceous compounds (granites, mica, porphyries, feldspars), KCl in the form of the mineral sylvite, and in the form of the minerals carnallite and kainite (a mixture of various salts of potassium and magnesium) in Saxony and Alsace. In the USSR, there are the world's richest deposits of potassium salts near Solikamsk (Urals). Potassium is further contained in seawater, in plant ash, and in saltpeter. Potassium salts are retained in the soil in greater quantities than sodium salts (the latter is more abundant in seawater); from the soil, potassium enters plants, where it is found mainly in the form of salts of organic acids (e.g., acid potassium oxalate-C₂HKO₄; acid potassium tartrate-cream of tartar-C₄H₅KO₆); in the ash obtained by burning plants, potassium is found in the form of potash (K₂CO₃). Without potassium salts, the development of plants is impossible; hence the frequent necessity of fertilizing soils due to a deficiency of potassium compounds in them (with manure, animal waste, etc.). [Note: The text contains a large, garbled table regarding a pregnancy calendar which is unrelated to the article content and appears to be an OCR error from an adjacent page]. In the animal organism, sodium predominates over potassium in quantity. At the same time, as a rule, cells contain more potassium, while body fluids (blood serum, lymph, and intercellular juices) contain more sodium. Thus, the blood serum of most mammals contains about 0.025% potassium (calculated as K₂O). In erythrocytes, the ratios are quite different: for example, in the horse, pig, and rabbit, sodium is absent (Bunge, Abderhalden), and K₂O is contained from 0.33% to 0.52%; for the cow, sheep, and goat, K₂O:Na₂O = 0.07%:0.23%; in humans, K₂O:Na₂O = 0.4%:0.075% (Sollmann). For muscles, K:Na = from 0.25-0.4%:0.06-0.16% (Palladin); for the gray and white matter of the brain, K:Na = 0.34%:0.20-0.22%. According to other data (Kober), human blood serum contains 0.884% NaCl, 0.038% KCl, 0.013% NaHCO₃, 0.0285% CaCl₂. According to Abderhalden, KCl is 0.04%; according to Meyer and Gottlieb, 0.025-0.03%. In the daily human diet, there is approximately 3-4 g of K₂O for every 5-8 g of Na₂O; the figures vary; plant food is richer in potassium salts. According to modern data (Macleod, Maccallum), the distribution of potassium within the cells themselves is localized unevenly, which undoubtedly has great biological (not yet fully clarified) significance (in the sense of surface energy, cell permeability); thus, potassium is more concentrated on the surface of cells, in the axons of nerve cells, on the periphery of the contractile substance of muscles, and on the surface of tubular cells of the kidneys; it is absent in nerve cells and in cell nuclei. Locally on mucous membranes, for example, of the gastrointestinal tract, potassium salts exhibit a directly irritating as well as a reflex action, more sharp than the corresponding sodium salts. This is explained partly by a general factor—the "salt," osmotic influence of the introduced salt (especially in concentrated solution), and partly by the rapidity of the penetration of potassium salts into the surrounding tissues, which can sometimes give rise to violent and even life-threatening reflex influences. Potassium salts, not bound to slowly diffusing acids, are easily absorbed and very rapidly excreted, mainly with urine. From 15% to 25% is excreted in feces. Tissues and interstitial spaces serve as a vast reservoir for the temporary retention of excess potassium salts before their excretion from the organism. The average ratio in urine of Na:K is from 2:1 to 5:3. During starvation, the ratios are reversed, reaching up to 1:3 (Sollmann). With an increase in the content of potassium salts in the blood serum, starting from 0.06%, toxic phenomena appear—symptoms of paralysis of the central nervous system, heart, and skeletal muscles; at a concentration of 0.1-0.2%, cardiac arrest occurs rapidly. The tone of smooth muscles (intestines, uterus, bronchi) generally increases. Regarding the effect on vascular tone, views differ: some attribute to potassium a lowering of vascular tone, others (Gramenitsky)—an increase in general vascular tone as a result of more sharp constriction of peripheral vessels and less sharp relaxation of internal vessels. The latter view can more easily explain the increase in blood pressure that occurs at the beginning of the toxic action of potassium. The diuretic effect of potassium salts, in addition to its property of easily "penetrating" and "loosening" cell membranes, should be linked to the "redistribution" of blood: constriction of vessels on the periphery and greater blood filling of internal organs, including the kidneys (Gramenitsky). Furthermore, the diuretic effect depends on the "salt" action of potassium salts. According to modern views (Meyer, Gottlieb), it consists of the removal ("liberation") of water by the introduced salts from plasma colloids ("extrarenal hydremia") and the hindrance of the reabsorption of urinary fluid from the renal tubules.

Characteristic of the effect on the heart are a slowing of the rhythm, a drop in tone, and diastolic arrest; the muscle still responds with a contraction to electrical stimulation. In particular, according to some data (Kisch, Sollmann), initially acting doses of potassium increase the excitability of the main ("nomotopic") cardiac nodes (sinus nodes in the frog), and only large doses paralyze them—in contrast to calcium salts, which excite them; therefore, extrasystoles and group-like cardiac contractions produced by medium doses of calcium (as a symptom of the excitation of "heterotopic" nodes, nodes of the "third order") can be successfully eliminated in an experiment by potassium salts. It can be considered that potassium salts contained in the blood under normal conditions participate in maintaining the normal rhythm of the heart, preventing the onset of ventricular or auricular rhythm. On an isolated frog heart, the conditions for the onset of a peculiar phenomenon—the so-called paradoxical action of potassium—have been studied: rapid cardiac arrest when changing the nutrient fluid, which is devoid of potassium salts (or almost devoid of them), to a normal one; the phenomenon has not yet been fully clarified; one of the reasons is the suddenly occurring change in the concentration of potassium, the "poison potential," in the heart, which corresponds to the "entry phase" according to Kravkov. The main phenomena during the action of potassium on the heart (see above) very much resemble the effect of irritation of the cardiac vagus nerve. Some authors even consider them identical. According to data from Howell and Duke, irritation of the vagus nerve for 1/2–1 minute releases 0.4–0.5 mg of potassium in the heart. According to Zondek, the vagal effect on the heart is realized precisely through such a mobilization of potassium; in other words, potassium for the vagus nerve (like calcium for the sympathetic nerve) is a chemical means of transmitting action ("humoral transmission," an idea close to modern theories about heart hormones by Loewi and Haberland). In this form, Zondek's view cannot be considered correct, since nerve irritation is undoubtedly accompanied by other phenomena in the innervated organ as well, such as: a change in cellular colloids, cellular permeability, and active reaction (Asher, Macleod, and others); the possibility of obtaining the paradoxical action of potassium even on an atropinized heart also speaks against the identity of the action of potassium and the vagus nerve. Among the mineral components of the animal body, potassium, or rather the potassium ion, is absolutely necessary precisely for "physiological balancing," for the "isoionia" of solutions, and for the mutual "ionic detoxification" of substances dissolved in and nourishing the cell. In round figures, in isoionic solutions (for warm-blooded animals), the ratios of NaCl:KCl:CaCl₂ are expressed by the coefficients 100:1:1–1.5 (see Ions, physiological action). Biologically, it is interesting for comparing the living conditions of animal body cells of land animals with the living conditions of sea dwellers to compare the quantities of the most important salts in the nutrient fluid (of the Ringer-Locke type) with their quantities in seawater; thus, for every 100 molecules of NaCl, there are: in Ringer-Locke fluid—KCl 1.7–2.4, CaCl₂ 1.1–1.6; in seawater—KCl 2.2, CaCl₂ 2.3. According to data from the most diverse experiments, the role of potassium as a physiological antagonist stands out clearly, especially in relation to calcium. This is proven, among other things, by the ability of potassium, in contrast to calcium, to physico-chemically "loosen" and physiologically make cell membranes more permeable; the ability to act on the heart vagotropically, ensuring a normal diastole (calcium's action is sympathicotropic, "systolic"); and to maintain a certain tone, mainly via a peripheral pathway, partly through the centers of the parasympathetic nervous system (calcium—via the sympathetic). As one of the latest examples of the antagonism of potassium to calcium, it can be pointed out that CaCl₂, introduced into the region of the tuber cinereum (for example, in a cat), causes a sleep-like state and even narcosis; KCl causes muscular hypertonia, excitation, and even convulsions. The physiological properties manifested by potassium are attributed by Zwaardemaker to the radioactivity of potassium—the only radioactive substance of protoplasm; the effects produced by potassium (emitting gamma and especially beta rays) have been experimentally obtained with equiradioactive quantities of other substances (even with alpha rays). However, the specific role of potassium ions in the organism cannot be disputed (Fröhlich). In view of the rapid absorption of potassium that has entered the blood by tissues and its excretion by the kidneys, poisoning per os with potassium salts is very rare (i.e., a toxic concentration is rarely reached). However, in cases of renal insufficiency (nephritis, arteriosclerosis, experimental uranium nephritis in rabbits), the organism becomes more sensitive to administered potassium, and toxic phenomena (cyanosis, weak pulse, vomiting) may occur. In animals with a high potassium content in erythrocytes and in humans, conditions are present during acute hemolysis and extensive bloody crushing of tissues for intoxication by potassium ions. Potassium salts introduced for medical purposes, in which the physiological action of the potassium cation is not surpassed or masked by a more active anion (these are mainly Kalium chloratum, sulfuricum, aceticum, nitricum, bitartaricum), must be evaluated from the point of view of salt action (influence on diffusion, osmosis, or laxative, diuretic, inflammatory, irritating action) and as the action of the potassium ion after absorption. The introduction of potassium into the blood must be considered a dangerous method in view of the possibility of acute cardiac arrest. The mechanism of the diuretic action of potassium salts can be experimentally deduced—apart from the "loosening" action of potassium on cell membranes—from the above-noted "redistribution" of blood (increase in vascular tone in the periphery and decrease in internal organs, or greater blood flow through the kidneys), as well as "salt diuresis." Indications of successful attempts to use potassium salts for certain liver diseases, apart from the osmotic influences of potassium salts, can be attributed to similar factors. In some forms of cardiac arrhythmias based on the overexcitation of intracardiac nerve nodes of the "third order" ("heterotopic"), the use of small doses of potassium salts may find experimental justification. Even more experimentally justified must be considered the use of potassium salts in heart diseases accompanied by insufficiency of cardiac diastole, and for deepening the diastolic, vagal action of specific cardiac agents. Finally, the therapeutic benefit of a plant-based diet, which ensures a significant amount of potassium salts and their relatively slow, uniform entry into the blood, must be evaluated, among other things, from the indicated points of view. Potassium preparations: 1. Kalium aceticum (Ph VII)—potassium acetate, CH₃COOK, a white crystalline powder, easily deliquescing in air, soluble in 0.4 parts of water and 4 parts of alcohol. Kal. acet. solutum (Ph VII), Liq. Kal. acetici—1 part of salt to 2 parts of water; from 5 to 30 g per day, mainly for diuretic action (and also cardiac—see above). 2. K. bitartaricum depuratum, Cremor Tartari (Ph VII)—acid potassium tartrate, purified, CH(OH)COOK, solid white or slightly grayish crystals, of acid taste; dissolve in 220 parts of cold and 20 parts of boiling water. Doses as a diuretic—1–2 g per dose, as a laxative—5 g. 3. K. tartaricum, s. Tartarus tartarisatus—neutral potassium tartrate, CH(OH)COOK + 1/2H₂O; unpleasant taste; as a laxative—in doses of approx. 2 g. 4. Natrium-Kalium tartaricum (Ph VII), s. Tartarus natronatus, s. Sal Seignetti—sodium potassium tartrate, Seignette salt, CH(OH)COOK + 4H₂O; crystals, well soluble in water (1:1.5). As a laxative—5–10 g; as a diuretic—0.5–2 g. It is part of Fehling's solution, Infus. Sennae compositum, and Pulvis aerophorus laxans. 5. K. chloratum—potassium chloride, KCl, crystals, soluble at 15° in 3 parts of water. Little used. 6. K. nitricum (Ph VII)—potassium nitrate, common saltpeter, KNO₃, colorless crystals, almost insoluble in alcohol, soluble in 4 parts of cold water and 0.5 parts of boiling water; solutions of neutral reaction. As a diuretic—in aqueous solution 5.0:200.0. Saltpeter paper, Charta nitrata, is prepared from K. nitricum; the smoke from its burning is inhaled for bronchial asthma. 7. K. sulfuricum (Ph VII)—potassium sulfate, K₂SO₄, crystals, soluble in 10 parts of cold and 4 parts of boiling water, insoluble in alcohol. As a laxative in doses of 1–2 g. 8. K. sulfuratum (Ph VII)—liver of sulfur, a mixture of various sulfur compounds of potassium [mainly trisulfide (K₂S₃)]. In a freshly prepared state, a brown, then greenish-brown powder, deliquescing in air, with a strong odor of hydrogen sulfide. For baths—50–100 g per 1 bath for chronic rashes, for sycosis; to reduce irritation, it is advised to add 100–200 g of gelatin.