Poisoning, Incompatibles: Same as for iodine, see page 683.

Potassii Nitras. Potassium Nitrate, KNO3. - (Syn., Pot. Nitras, Saltpetre, Nitre, Nitras (Potassicus) Kalicus, Sal (Petrseae) Nitri, Nitrum Depuratum; Fr. Azotate (Nitrate) de Potasse, Nitre prismatique; Ger. Kalium nitricum, Kaliumnitrat, Salpetersaures Kali, Kalisalpeter.) Manufacture: While this may be made by neutralizing nitric acid with potassium carbonate, yet by far the greater part of that used is found as a neutral salt in Chile, Peru, India, etc. Some of this supply, however, is a product of nitre beds, which consist of a mechanical mixture of animal refuse, earth, and lime, protected under cover. By putrefaction ammonia is formed, which, upon oxidation, becomes nitric acid and unites with the calcium; this is dissolved out and decomposed with potassium carbonate or chloride - Ca(NO3)2 + K2CO3 = 2KNO3 + CaCO3. Saltpetre may also be obtained from Chile saltpetre by double decomposition - NaNO3+KCl = KNO3+NaCl. It is colorless, transparent, 6-sided, rhombic prisms, or white crystalline powder, odorless, saline taste, with cooling sensation in the mouth, slightly hygroscopic, soluble in glycerin, water (2.8), boiling water (.5), alcohol (620); aqueous solution (1 in 10) neutral; contains, when dried, 99 p. c. of pure salt. Tests': 1. Heat strongly - melts without decomposition; at higher heat - evolves oxygen, partly reduced to nitrite; heated with charcoal - deflagrates. 2. Aqueous solution (1 in 20) with sodium bitartrate T. S. - white crystalline precipitate; aqueous solution (1 in 10) with 1 drop of diphenylamine T. S. + sulphuric acid slowly added to form separate layer - deep blue at line of contact. Imparities: Heavy metals, chlorate, perchlorate. Should be kept in well-closed containers. Dose, gr. 10-30 (.6-2 Gm.).

Preparation. - (Unoff.): Charta Potassii Nitratis, official 1880-1900; potassium nitrate 20, water 80; immerse in solution strips of white, unsized paper, dry, keep in well-closed containers.

Fig. 446. - Potassium nitrate crystal.

PROPERTIES. - Refrigerant, diuretic, diaphoretic, antiseptic, purgative, nervous sedative, cardiac depressant (causing fewer and feebler heats), irritant, alterative; enters blood unchanged; eliminated by kidneys unchanged.

Uses. - Acute rheumatism, pneumonia, fevers (acetate and citrate preferable), dropsy, stomatitis, bronchitis, freckles, bruises, abrasions, scurvy, angina, asthma, gout, gonorrhoea, incontinence of urine, manufacture of gunpowder. The once official charta mostly burnt for asthma.

Potassii Permanganas. Potassium Permanganate, KMnO4. - (Syn., Pot. Permang., Hypermanganas (Potassicus) Kalicus; Fr. Permanganate de Potasse; Ger. Kalium permanganicum, Kaliumpermanganat, Uebermangansaures Kali.)

Manufacture: Fuse manganese dioxide with potassium carbonate (or hydroxide) and potassium chlorate (or nitrate). The manganese is converted into manganic acid, which, combining with the alkali, forms potassium manganate; this can be dissolved out by water, giving a dark emerald-green solution, and crystallized. If this solution now be acidified (H2SO4) or boiled with much water, it becomes red and contains in solution KMnO4 and a precipitate of MnO2 - (1) 3MnO2 + 3K2CO3 + KC1O3 = 3K2MnO4 + KC1+3CO2. (2) 3K2MnO4 + 2H2SO4=2KMnO4+ 2K2SO4 + MnO2 + 2H2O, or 3K2MnO4 + 2H2O = 2KMnO4 + MnO2 + 4KOH. It is in slender, mono-clinic prisms, dark purple color, almost opaque by transmitted light, blue metallic lustre by reflected light, odorless, sweet, disagreeable, astringent taste (in solution), permanent, soluble in water (13.5), boiling water (3.5), decomposed by alcohol; when heated decrepitates; at 240° C. (464° F.) decomposes, yielding oxygen, potassium manganate, and manganese dioxide; contains, when dried, 99 p. c. of pure salt. Tests: 1. Aqueous solution, rose to deep violet-red, has color discharged by hydrogen sulphide, ferrous sulphate, oxalic acid, alcohol, etc., especially if acidified by sulphuric acid. Should be kept in glass-stoppered bottles, and when dry or in solution must not be brought in contact with organic or other readily oxidizable substances. Dose, gr. 2-5 (.13-.3 Gm.), given on a full stomach in much water, or pill made with kaolin, soft paraffin, or wool fat.

Preparation. - (Unoff.): Liquor Potassii Permanganatis (Br.), 1 p. c. Dose, 3ij-4 (8-15 Ml. (Cc.)).

Properties. - Disinfectant, deodorant, antiseptic, caustic, stimulant, emmenagogue; liberates much of its oxygen as ozone.

Uses. - Externally - fetid and gangrenous ulcers, wounds, abscesses, carbuncles, gonorrhoea, leucorrhoea, otorrhoea, diphtheria, cancerous

Fig. 447. - Potassium permanganate crystal.

ulcers, eczema. Internally - diphtheria, scarlatina, atonic amenorrhoea, antidote to morphine, opium (by mouth; of little value by rectum, and still less hypodermically), phosphorus, serpents' bites and rabies poisoning. The stains can be resolved by weak acid solutions (oxalic, hydrochloric), lemon juice, etc. It oxidizes to the extent of its available oxygen, forming harmless compounds.

Acidum Hydrocyanicum Dilutum. Diluted Hydrocyanic Acid, HCN. - (Syn., Acid. Hydrocyan. Dil., Diluted Prussic Acid, Acidum Hydrocyanatum (Borussicum), Cyanhydric Acid; Fr. Acide cyan-hydrique (hydrocyanique); Ger. Cyanwasserstoffsaure, Blausaure.) An aqueous solution containing 1.9-2.1 p. c. of HCN, and not more than .1 p. c. of HC1.

Manufacture: 1. Extemporaneously. - Mix diluted hydrochloric acid 15.54 Ml. (Cc.) with distilled water 44.10 Ml. (Cc), add silver cyanide 6 Gm., shake, reject the precipitate - AgCN + HC1 = HCN + AgCl. 2. Commercially. - Heat potassium ferrocyanide 20 Gm. + sulphuric acid 8 Ml. (Cc.) + water 65 Ml. (Cc), pass evolved gas into distilled water 65 Ml. (Cc). It is a colorless liquid; characteristic odor (resembling bitter almond); acid reaction, volatile, very unstable and poisonous; use care in handling and tasting. Tests: 1. Render 1 Ml. (Cc) alkaline with potassium hydroxide T. S., + few drops of ferrous sulphate T. S., boil, acidulate with hydrochloric acid - blue precipitate. 2. Evaporate 10 Ml. (Cc) - residue .002 Gm. Impurities: Hydrogen chloride, etc Should be kept in small, dark amber-colored, well-stoppered vials. Dose, ej-3 (.06-.2 Ml. (Cc)), in water or alcohol. An acid of 5 p. c is manufactured, but it is even less stable and reliable than the official.