Properties. - Hydrocyanic acid and all cyanides: Anaesthetic, sedative, anodyne, antispasmodic. On unbroken skin, mouth, and stomach paralyzes sensory nerve-endings; small doses slow the heart by stimulating inhibitory centres; large doses may cause diastolic arrest (instantaneous death) by paralyzing the heart directly, and cardiac centre in the medulla. Quickly enters blood, causing all to be bright red (arterial tint), then going to dark venous color. The venous becomes red, owing to its haemoglobin being oxidized; the arterial becomes dark, owing to its oxygen being replaced by carbon dioxide; may produce dermatitis.

Uses. - Phthisis, dyspnoea, cough, asthma, whooping-cough, chronic catarrh, nervous cough, angina pectoris, gastralgia, skin diseases.

Poisoning: Symptoms established within a half to two minutes - giddiness, stupor, complete insensibility, eyes fixed, glistening, pupils dilated, dyspnoea, limbs flaccid, skin cold, clammy, respiration slow, deep, convulsive, pulse weak, slow, almost imperceptible, convulsions, paralyzed spine, death from asphyxia (from paralysis of respiratory centre), breath has bitter almond odor. If possible, wash out stomach, emetics, atropine hypodermically, gr. 1/50 (.0013 Gm.), ether, brandy, ammonia inhalations, chlorine water, artificial respirations and heat, cold water alternately on chest and spine, electricity; ferrous and ferric sulphates, followed by K2CO3 solution = insoluble Prussian blue (antidote). Rapidly eliminated by lungs and kidneys.

Incompatibles: Atropine, diffusible stimulants; copper, iron, and silver salts, cobalt nitrate, red mercuric oxide and sulphide.

Synergists: Cardiac and motor depressants.

Allied Salts:

1. Potassii Cyanidum. Potassium Cyanide, KCN, official 1820-1910. - Obtained by passing hydrocyanic acid gas (potassium ferro-cyanide (2) -+- sulphuric acid q. s.) into solution of potassium hydroxide in alcohol (1 in 5-6), washing precipitate with alcohol, or heat together potassium carbonate and potassium ferrocyanide - K2CO3 + K4Fe-(CN)6 = 5KCN + KCNO + Fe + CO2. May remove cyanate with alcohol or carbon disulphide, and, as the iron is precipitated to the bottom of iron retort, must, in pouring out the mass, stop short of any iron contamination. It is in white, opaque, amorphous pieces, white granular powder, without odor (dry), or of hydrocyanic acid (moist), sharp alkaline taste, deliquescent, soluble in water (2), sparingly in alcohol; contains 95 p. c. of pure salt. Impurities: Carbonate (HC1), ferrocyanide (Fe2Cl6, blue), sulphocyanates (Fe2Cl6, red); should be kept in well-stoppered bottles labelled poison, and handled with great care. Sedative, antispasmodic, anodyne - similar to hydrocyanic acid as poison and medicine; headache from dyspepsia, menstruation, etc. Dose, gr. 1/16-1/8 (.004-.008 Gm.), in water.

2. Potassii Ferrocyanidum. Potassium Ferrocyanide, K4Fe(CN)6 + 3H2O, official 1820-1910. - Obtained by heating together potassium carbonate (pearl-ash), nitrogenous animal refuse (dried blood, hoofs, etc.), and iron scraps; the fused mass (melt) is lixiviated and this solution evaporated for crystallization - (1) 6KCN + Fe + 2H2O = K4Fe(CN)6 + 2KOH + H2, or (2) 6KCN + FeS = K4Fe(CN)6 + K2S. Now very largely obtained from the mass of ferric hydroxide used to purify illuminating gas, as that absorbs cyanogen compounds forming ferrocyanides, etc. It is in large, soft, transparent, yellow, 4-sided, monoclinic tabular crystals or prisms, odorless, mild saline taste, soluble in water (4), insoluble in alcohol, efflorescent; contains 99 p. c. of pure salt. Impurities: Carbonate, ferricyanide. Not used much medicinally, although it is non-poisonous when pure; sometimes valuable in checking colliquative sweats of phthisis; important test reagent for copper, zinc, and ferric salts; chief source of cyanogen compounds.

3. Potassii Carbonas Impura. Impure Carbonate of Potassium, official 1830-1860 (pearl-ashes, pearl-ash). - This is simply the crude potash salts, black salts, derived from the evaporated lye of wood-ashes, subjected to direct flame in an oven-shaped furnace. By this means all combustible impurities are burnt out, and the mass, from

Fig. 448. - Potassium ferrocyanide crystal.

being black, becomes of a bluish-white color. It is still official in Germany as Kalium carbonicum crudum, Pottasche.

4. Potassii Dichromas. Potassium Dichromate, K2Cr2O7, official 1860-1910. - Obtained by heating together potassium carbonate, lime, and powdered chrome iron ore which has previously been roasted; the iron is oxidized into ferric oxide, and chromium into chromic acid; this latter attacks the potassium carbonate forming the neutral chro-mate, which is treated with an acid (H2SO4 or HNO3) to get the acid or bichromate - (1) 2FeOCr2O3 + 4K2CO3 + O7 = Fe2O3 + 4CO2 + 4K2CrO4. (2) 2K2CrO4 + H2SO4 = K2Cr2O7 + K2SO4 + H2O. It occurs in large, orange-red, transparent, triclinic prisms, or 4-sided tabular crystals, odorless, acidulous metallic taste, soluble in water (9), insoluble in alcohol, permanent; contains 99 p. c. of pure salt. Tests: 1. At white heat evolves oxygen, leaving neutral potassium chromate and green chromic oxide. 2. Sodium cobaltic nitrate T. S. - yellow precipitate. Irritant, caustic, alterative, expectorant; secondary syphilis; externally - caustic in tubercular enlargements, excrescences, warts, syphilitic sores, sloughing wounds; largely in calico-printing, pigments, etc.; employees in its manufacture often suffer from ulcers on hands, face, nares, etc., from the irritating fumes. Poisoning: Have a violent irritative, corrosive condition; vomiting, hemorrhagic dejections, abdominal pains, dilated pupils, great depression, collapse, poor circulation, coma, heart failure, death. Give emetic, alkaline carbonate (bicarbonate), or magnesium oxide, chalk, demulcent drinks, milk, egg-white, stimulants, heat, opium. Should be kept in well-stoppered containers. Dose, gr. 1/5 (.0013 Gm.), in pill.

5. Potassii Sulphas. Potassium Sulphate, K2SO4, official 1820-1910. - Obtained by decomposing potassium carbonate, nitrate, or chloride with sulphuric acid, or by neutralizing sulphuric acid with potassium hydroxide, or from kainite, but its greatest source is as a by-product in the manufacture of nitric acid - (1) K2CO3 + H2SO4 = K2SO4 + H2O + CO2. (2) 2KC1 + H2SO4 = 2HC1 + K2SO4. (3) 2KNO3 + H2SO4 = K2SO4+ 2HNO3. (4) KNO3 + H2SO4 = KHSO4 + HNO3. In this last formula the acid sulphate has to be converted into normal sulphate - 2KHSO4+K2CO3 = 2K2SO4 + CO2 + H2O. It is in hard, colorless, transparent, 6-sided, rhombic prisms, terminated by pyramids, or in a white powder, odorless, bitter, saline taste, permanent; soluble in water (9), insoluble in alcohol; contains 99 p. c. of pure salt. Impurities: Heavy metals, arsenic. Mild purgative cholagogue, operating usually without pain, heat, or perceptible

Fig. 449. - Potassium dichromate crystal.

Fig. 450. - Potassium sulphate crystal.

irritation; given after labor and for drying up mammary secretion, dyspepsia, biliousness, albuminuria. Owing to hardness, it is used tor pulverizing tough vegetable substances, like ipecac, etc. Usually prescribed with rhubarb, etc. Dose, 3ss-4 (2-15 Gm.).

6. Potassii Sulphis. Potassium Sulphite, K2SO3.2H2O, official 1870-1890. - Obtained by passing SO2 through solution of K2CO3 until the CO2 is expelled, then adding equal weight of K2CO3, after which sulphite crystallizes out. It is in opaque octahedral crystals or crystalline powder, odorless, deliquescent, bitter, saline, sulphurous taste; used like sulphites of sodium and magnesium, to which it is inferior. Dose, as a laxative, 3ij - 4 (8-15 Gm.).

7. Potassii Tartras. Potassium Tartrate, K2C4H4O6,H2O, official 1880-1890. - Obtained by gradually adding to a solution of potassium carbonate (preferably bicarbonate) acid tartrate of potassium until neutral, filtering, concentrating, setting aside to crystallize - 2KHC4-H4O6 + K2CO3 = 2K2C4H4O6,H2O+ CO2. Diuretic, purgative, aperient; more gentle than sodium or magnesium sulphate; hepatic and portal congestion, hemorrhoidal swellings, febrile diseases. Dose, 3j-8 (4-30 Gm.).

8. Potassii Chloridum. Potassium Chloride, KC1. - Obtained at Stassfurt from carnallite, double chloride of potassium and magnesium. In colorless, elongated crystals, granular powder, odorless, saline. Employed largely in manufacturing potassium salts.