Pbii = 207.10.

(Syn., Fr. Plomb; Ger. Blei.)

The element lead (AS. lead, heavy weight, plummet, L. plumbum), official 1820-1830, is obtained mostly from native sulphide (galena), PbS, by roasting in a reverberatory furnace: (1) PbS + O3 = PbO + SO2. (2) PbS + O4 = PbSO4. (3) PbS + 2PbO = 3Pb + SO2. (4) PbS + PbSO4 = 2Pb + 2SO2; or heat sulphide with iron - PbS + Fe = FeS + Pb. Lead is a soft, fusible, heavy metal, sp. gr. 11.45, entering into the alloys of solder, shot, Britannia metal, type-metal, etc.

Tests for Lead Salts: 1. H2S or NH4SH precipitates insoluble black sulphide. 2. H2SO4, or soluble sulphate, precipitates white lead sulphate, insoluble in HNO3. 3. Alkaline carbonates precipitate white basic lead carbonate insoluble in excess.

Plumbi Oxidum. Lead Oxide, PbO. - (Syn., Plumb. Oxid., Litharge, Oxide (Flowers) of Lead, Semi-vitrified Lead Oxide, Plumbum Oxyda-tum, Plumbi Oxidum Semi-vitreum; Fr. Oxyde de Plomb fondu, Protoxyde de Plomb; Ger. Lithargyrum, Bleiglatte, Bleioxyd.)

Manufacture: Heat metallic lead to whiteness (400-450° C; 752-842° F.) in the air, the oxygen of which combines with the lead, forming lead oxide, while any silver present remains unchanged; if heated only to fusion, get yellow amorphous massicot, a less oxidized form. It is a heavy, reddish-yellow powder, or in minute scales, odorless, tasteless, on exposure absorbs moisture and CO2, insoluble in alcohol, nearly so in water, soluble in acetic acid, diluted HNO3, or warm solutions of fixed alkali hydroxides; heated with charcoal yields the metal; contains, when freshly ignited, 96 p. c. of the pure salt. Tests: 1. Solution in diluted nitric acid (1 in 10) is colorless, when nearly neutralized by ammonia water, + hydrogen sulphide T. S. - black precipitate, + potassium iodide T. S. - yellow precipitate, + diluted sulphuric acid - white precipitate. Impurities: Carbonate, moisture. Should be kept in well-closed containers.

Preparation. - 1. Liquor Plumbi Subacetatis, 11 p. c.

Properties and Uses. - Chiefly externally and in combination, for burns, abraded surfaces, to allay inflammations; also enters into paints, flint glass, glazing of pottery, etc.; with KOH as caustic in condylomata, warts of glans penis and vagina, producing a superficial black slough. The emplastrum to prevent bed-sores, abrasions; if surface be large, plaster usually is substituted to avoid poisoning.

Plumbi Acetas. Lead Acetate, Pb(C2H3O2)2 + 3H2O. - (Syn., Plumb. Acet., Sugar of Lead, Acetas Plumbicus, Saccharum Saturni,

Cerussa Acetata; Fr. Acetate - Sucre de Plomb, Sucre - Sel de Saturne; Ger. Plumbum aceticum, Bleiacetat, Essigsaures Bleioxyd, Bleizucker.)

Manufacture: Act upon lead oxide (1) with 30 p. c. acetic acid (2), evaporate, crystallize - PbO +

2HC2H3O2 + heat = Pb(C2H3O2)2 + H2O; or expose lead plates to the combined action of air and vinegar.

It is in colorless, shining, transparent, monoclinic prisms or plates, or heavy, white, crystalline masses, granular crystals, faintly acetous odor, sweetish, astringent, metallic taste, efflorescent, absorbing carbon dioxide, soluble in glycerin, water (1.4), boiling water (.5), alcohol (38); at 40° C. (104°

F.) loses water of crystallization, at 75° C. (167° F.) fuses in its water of crystallization, at 280° C. (536° F.) decomposes into lead mixed with lead oxide; contains 85.31-89.57 p. c. of anhydrous lead acetate, corresponding to 99.5 p. c. of crystallized salt. Impurities: Iron, copper, carbonate. Should be kept in well-closed containers. Dose, gr. 1/2-4 (.03-26 Gm.), usually with opium.

Preparations. - 1. Liquor Plumbi Subacetatis. Solution of Lead Subacetate. (Syn., Liq. Plumb. Subacet., Goulard's Extract, Acetum Plumbicum (Saturni), Plumbum Hydrico-aceticum Solutum; Br. Liquor Plumbi Subacetatis Fortis; Fr. Sous-acetate de Plomb liquide, Extrait de Saturne (de Goulard), Vinaigre de Plomb (de Saturne); Ger. Liquor Plumbi subacetici, Bleiessig.)

Manufacture: Dissolve lead acetate 18 Gm. in boiling distilled water 70 Ml. (Cc.), add it slowly, in portions, to lead oxide 11 Gm., previously rubbed to smooth paste with distilled water 10 Ml. (Cc); boil half an hour, stirring occasionally, preserving volume by adding a little distilled water, cool, filter, add boiled, cooled distilled water q. s. 100 Gm. It is a clear, colorless, aqueous liquid, odorless, very sweet, astringent taste, alkaline to litmus but not to phenolphthalein, on exposure absorbs carbon dioxide causing white precipitate, sp. gr. 1.245; contains lead subacetate corresponding to 18 p. c. of lead. Tests: 1. Aqueous dilution (1 in 10), using recently boiled distilled water, with (a) hydrogen sulphide - black precipitate, (6) potassium iodide T. S. - yellow precipitate, (c) diluted sulphuric acid - white precipitate. Impurities: Iron, copper, normal lead acetate. Should be kept in well-stoppered bottles.

Fig. 461.   Lead acetate crystal.

Fig. 461. - Lead acetate crystal.

Preps.: 1. Liquor Plumbi Subacetatis Dilutus. Diluted Solution of Lead Subacetate. (Syn., Liq. Plumb. Subacet. Dil., Lead Water, Goulard's Lotion (Water), Aqua Plumbica (Saturnina); Fr. Eau de Saturne, Eau blanche; Ger. Aqua Plumbi, Bleiwasser, Kuhlwasser.) Manufacture: Mix solution of lead subacetate 4 Gm. with distilled water, previously boiled and cooled, q. s. 100 Gm. It is an aqueous liquid containing 1 p. c. of lead subacetate. Should be kept in small, well-filled, tightly-stoppered bottles. 2. Emplastrum Plumbi. Lead Plaster. (Syn., Emp. Plumb., Diachylon Plaster, Litharge Plaster, Emplastrum Diachylon Simplex, Emplastrum Album Coctum; Fr. Emplastrum Simplex, Emplatre simple (de Plomb - de Litharge); Ger. Emplastrum Lithargyri (Simplex), Bleipflaster, Emplastrum Cerussae, Bleiweisspflaster.)

Manufacture: Heat olive oil 100 Gm. + lard 100 Gm. until liquefied, sift lead oxide 100 Gm., through (80) sieve, upon surface of hot liquid, mix thoroughly, add gradually boiling water 35 ML (Cc), boil, constantly stirring and adding water occasionally, until mass homogeneous and a portion is pliable and tenacious in cold water; remove from fire and wash out glycerin with warm water (several times), free from water by kneading, roll into suitable size cylinders, and wrap in paper.