Edin. Lead.

Syn. Plomb(F.), Blei (G.), Lood (Dutch), Blye (Ban.), Bly (Swed.), Olow (Polish), Piombo (I.), Plorao (S.), Chumbo (Port.), Swinez (Russ.), Soorb (Pers.), Anuk (Arab.), Sisa.(H.), Eeeum (Tarn.), Sisaca (San.), Sheesh (Duk), Temaetain (Malay), Ak-kil-le-iook (Esquimaux).

1 Olivier's Travels (translation), ii. 90. Olivier says, a soft mastic, having all the qualities of mastic, except in its consistence, which is that of turpentine, is procured by engrafting the lentisck on the Chian turpentine tree.

2 Crell's Annals, 1794, ii. 185. Thomson's Chymistry, 4th edit. vol. v. 93.

3 See Mr. Matthew's experiments, Nicholson's Journ. vol. x. 247.

4 Hoffman (Obs. Phys. Chim. Select, p. 68.), however, states, that by rubbing the mastic in a mortar, with its weight of carbonate of potassa, and then distilling with alcohol, the liquid which comes over has both the smell and the taste of mastic.

This is a metal of a bluish grey colour, occurrihgi n great abundance in most countries of both hemispheres of the globe, in primitive, transition, and floetz formations.1 It is found,

Galena is the ore from which metallic lead is commonly procured. When brought up from the mine, the ore is broken in pieces, and the impurities, which are mostly iron pyrites, quartz, calcareous spar, and clay, are separated by picking and washing: it is then exposed to a strong heat in a common re-verbatory furnace till the sulphur is all separated, after which the metal is brought into a state of fusion; and some spadefuls of lime being thrown in, the scoriae, which are thus rendered solid on the surface of the melted metal are raked to the side of the furnace, while the lead is run out into moulds through an aperture near the bottom; and in this state it is called pig-lead. It frequently contains silver which is separated by oxidizing the lead into litharge, and freeing the silver from what remains by cupellation.

Qualities.-Pure metallic lead is of a light bluish-grey colour, and immediately after being melted or cut has a very considerable degree of lustre, which it quickly loses on exposure to the air, owing to the formation of carbonate of lead on its surface. It is nearly insipid; and emits, when rubbed, a peculiar unpleasant odour. It stains the fingers and paper of a bluish colour, and has a specific gravity of 11.38, which is somewhat diminished after it is well hammered.1 It is the softest and least elastic of the solid metals; and although its ductility be trifling, yet it is very malleable, and may be reduced into thin leaves and drawn into wire: it melts at a temperature of 612°2, and at a greater heat is volatilized. Its susceptibility of oxidizement is very considerable : when it is exposed to the air at a high temperature, it is capable of uniting with three doses of oxygen, and forming three distinct oxides, each of which contains the following proportions of lead and oxygen3:-

1 The Harz mines yield annually 52 tons of lead. The Phrenic-inns exported lead from Cornwall and the Scilly Islands. - Strabo, 1. iii. p. 175.

Medical properties and uses,-Lead has no action on the animal system in its pure metallic taste : but when oxidized, or in combination with acids, it produces very deleterious effects. Hence, metallic lead taken into the stomach may prove a poison, from its meeting with carbonic acid in the primaee viae; and liquors which are apt to become in any degree acidulous, if kept in leaden cisterns, may, from the same cause, be productive of much danger to those who drink them. I know an instance of the officers of an East Indiaman having been nearly poisoned from drinking water which was kept in a leaden cistern, and which by the constant agitation of it, from the rolling of the ship, had carbonized the lead; and there have been instances, also, of plumbers being poisoned by the volatilized particles of lead, which are supposed in great part to form into a grey oxide; but it is more likely that they form a carbonate. Distilled and rain water, kept in leaden cisterns, form a carbonate of lead, and thence become poisonous; but hard water, or water containing any saline matter, prevents this effect, by forming an insoluble compound with the lead, which protects it from the action of the air.5 The greater number of cases of poisoning from this metal are produced from the preparation of it we are about to describe; and, therefore, the mode in which lead acts on the animal system will be more properly noticed under it than in this place.

1 Muschenbroek.

2 Irvine, Chymieal Essays, 35.

3 Thomson's System of Chymistry, 4th edit. i. 274-277.

4 This oxide was first discovered by Proust. Mr. Murray thinks there is reason for believing it to be a subsalt-System of Chymistry, iii. 266.

5See Christison on Poisons, p. 384.

1. Carbonate of Lead.

Officinal. Plumbi Carbonas, Lond. Carbonas Plumbi, vulgo, Cerussa, Edin. Dub, Carbonate of Lead. White Oxide of Lead. Ceruse.1 Syn. Plomb carbonate (F.) Bleiweiss ( G.), Loot wit (Swed.), Cerussa (I.),

Blanco de Plomo(S.), Asfeedas (Arab.), Suffida (H.), Vullay (Tarn.).

This substance, which is known in commercial language by the name of white lead, appears from the analysis of it by several of the most expert chymists, to be a carbonate of lead.2 It is prepared in various ways, of which the following is one:-Sheets of lead, about two feet long, five inches broad, and a quarter of an inch thick, cast in a mould, and not afterwards flattened, are rolled up into loose coils, and placed in earthen pots, which are wider at the mouth than at the bottom. Each pot is capable of holding six pints of fluid; but into it as much vinegar only is poured as will rise so high as not to wet the lead, which rests on a ledge half-way down. In some manufactories, however, the pots are made to contain about a pint of vinegar only; and the lead, instead of being coiled up, is in form of a simple plate, which is laid over the mouth of the pot. The vinegar and lead being arranged, the pots are buried in fresh stable litter, where they remain for about two months; during which time the vapours of the vinegar, elevated by the heat of the dung, oxidixe the surface of the lead, converting it into the yellow oxide, which combines with the carbonic acid gas evolved from the fermented materials of the bed.