The metal itself is not used in medicine. The chief pharmacopoeial salts are: (1) Plumbi oxidum (lead oxide), litharge. It is not used internally, but from it is made Emplastrum Plumbi (diachylon plaster), which is an oleate of lead and is contained in emplastrum hydrargeri, emplastrum plumbi iodidi, emplastrum resinae, emplastrum saponis. (2) Plumbi Acetas (sugar of lead), dose 1 to 5 grains. From this salt are made the following preparations: (a) Pilula Plumbi cum Opio, the strength of the opium in it being 1 in 8, dose 2 to 4 grains; (b) Suppositoria Plumbi composita, containing lead acetate, opium and oil of theobroma, there being one grain of opium in each suppository; (c) Unguentum Plumbi Acetatis; (d) Liquor Plumbi Subacetatis Fortior, Goulard’s extract, strength 24% of the subacetate; this again has a sub-preparation, the Liquor Plumbi Subacetatis Dilutis, called Goulard’s water or Goulard’s lotion, containing 1 part in 80 of the strong extract; (e) Glycerinum Plumbi Subacetatis, from which is made the Unguentum Glycerini Plumbi Subacetatis. (3) Plumbi Carbonas, white lead, a mixture of the carbonate and the hydrate, a heavy white powder insoluble in water; it is not used internally, but from it is made Unguentum Plumbi Carbonatis, strength 1 in 10 parts of paraffin ointment. (4) Plumbi Iodidium, a heavy bright yellow powder not used internally. From it are made (a) Emplastrum Plumbi Iodidi, and (b) Unguentum Plumbi Iodidi. The strength of each is 1 in 10.

Applied externally lead salts have practically no action upon the unbroken skin, but applied to sores, ulcers or any exposed mucous membranes they coagulate the albumen in the tissues themselves and contract the small vessels. They are very astringent, haemostatic and sedative; the strong solution of the subacetate is powerfully caustic and is rarely used undiluted. Lead salts are applied as lotions in conditions where a sedative astringent effect is desired, as in weeping eczema; in many varieties of chronic ulceration; and as an injection for various inflammatory discharges from the vagina, ear and urethra, the Liquor Plumbi Subacetatis Dilutum being the one employed. The sedative effect of lead lotion in pruritus is well known. Internally lead has an astringent action on the mucous membranes, causing a sensation of dryness; the dilute solution of the subacetate forms an effective gargle in tonsillitis. The chief use of the preparations of lead, however, is as an astringent in acute diarrhoea, particularly if ulceration be present, when it is usefully given in combination with opium in the form of the Pilula Plumbi cum Opio. It is useful in haemorrhage from a gastric ulcer or in haemorrhage from the intestine. Lead salts usually produce constipation, and lead is an active ecbolic. Lead is said to enter the blood as an albuminate in which form it is deposited in the tissues. As a rule the soluble salts if taken in sufficient quantities produce acute poisoning, and the insoluble salts chronic plumbism. The symptoms of acute poisoning are pain and diarrhoea, owing to the setting up of an active gastro-enteritis, the foeces being black (due to the formation of a sulphide of lead), thirst, cramps in the legs and muscular twitchings, with torpor, collapse, convulsions and coma. The treatment is the prompt use of emetics, or the stomach should be washed out, and large doses of sodium or magnesium sulphate given in order to form an insoluble sulphate. Stimulants, warmth and opium may be required. For an account of chronic plumbism see [Lead Poisoning].

Authorities.—For the history of lead see W. H. Pulsifer, Notes for a History of Lead (1888); B. Neumann, Die Metalle (1904); A. Rossing, Geschichte der Metalle (1901). For the chemistry see H. Roscoe and C. Schorlemmer, Treatise on Inorganic Chemistry, vol. ii. (1897); H. Moissan, Traité de chimie minerale; O. Dammer, Handbuch der anorganischen Chemie. For the metallurgy see J. Percy, The Metallurgy of Lead (London, 1870); H. F. Collins, The Metallurgy of Lead and Silver (London, 1899), part i. “Lead”; H. O. Hofmann, The Metallurgy of Lead (6th ed., New York, 1901); W. R. Ingalls, Lead Smelting and Refining (1906); A. G. Betts, Lead Refining by Electrolysis (1908); M. Eissler, The Metallurgy of Argentiferous Silver. The Mineral Industry, begun in 1892, annually records the progress made in lead smelting.

LEADER, BENJAMIN WILLIAMS (1831-  ), English painter, the son of E. Leader Williams, an engineer, received his art education first at the Worcester School of Design and later in the schools of the Royal Academy. He began to exhibit at the Academy in 1854, was elected A.R.A. in 1883 and R.A. in 1898, and became exceedingly popular as a painter of landscape. His subjects are attractive and skilfully composed. He was awarded a gold medal at the Paris Exhibition in 1889, and was made a knight of the Legion of Honour. One of his pictures, “The Valley of the Llugwy,” is in the National Gallery of British Art.

See The Life and Work of B. W. Leader, R.A., by Lewis Lusk, Art Journal Office (1901).

LEADHILLITE, a rare mineral consisting of basic lead sulphato-carbonate, Pb4SO4(CO3)2(OH)2. Crystals have usually the form of six-sided plates (fig. 1) or sometimes of acute rhombohedra (fig. 2); they have a perfect basal cleavage (parallel to P in fig. 1) on which the lustre is strongly pearly; they are usually white and translucent. The hardness is 2.5 and the sp. gr. 6.26-6.44. The crystallographic and optical characters point to the existence of three distinct kinds of leadhillite, which are, however, identical in external appearance and may even occur intergrown together in the same crystal: (a) monoclinic with an optic axial angle of 20°; (b) rhombohedral (fig. 2) and optically uniaxial; (c) orthorhombic (fig. 1) with an optic axial angle of 72¾°. The first of these is the more common kind, and the second has long been known under the name susannite. The fact that the published analyses of leadhillite vary somewhat from the formula given above suggests that these three kinds may also be chemically distinct.

Fig. 1.Fig. 2.

Leadhillite is a mineral of secondary origin, occurring with cerussite, anglesite, &c., in the oxidized portions of lead-bearing lodes; it has also been found in weathered lead slags left by the Romans. It has been found most abundantly in the Susanna mine at Leadhills in Scotland (hence the names leadhillite and susannite). Good crystals have also been found at Red Gill in Cumberland and at Granby in Missouri. Crystals from Sardinia have been called maxite.