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
7234°. 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. (L. J. S.)
LEADHILLS, a village of Lanarkshire, Scotland, 534 m.
W.S.W. of Elvanfoot station on the Caledonian Railway Company’s
main line from Glasgow to the south. Pop. (1901) 835.
It is the highest village in Scotland, lying 1301 ft. above sea-level,
near the source of Glengonner Water, an affluent of the Clyde.
It is served by a light railway. Lead and silver have been
mined here and at Wanlockhead, 112 m. S.W., for many centuries—according
to some authorities even in Roman days. Gold was
discovered in the reign of James IV., but though it is said then
to have provided employment for 300 persons, its mining has long
ceased to be profitable. The village is neat and well built, and
contains a masonic hall and library, the latter founded by the
miners about the middle of the 18th century. Allan Ramsay,
the poet, and William Symington (1763–1831), one of the earliest
adaptors of the steam engine to the purposes of navigation, were
born at Leadhills.
LEAD POISONING, or Plumbism, a “disease of occupations,”
which is itself the cause of organic disease, particularly of the
nervous and urinary systems. The workpeople affected are
principally those engaged in potteries where lead-glaze is used;
but other industries in which health is similarly affected are file-making,
house-painting and glazing, glass-making, copper-working,
coach-making, plumbing and gasfitting, printing, cutlery,
and generally those occupations in which lead is concerned.
The symptoms of chronic lead poisoning vary within very wide limits, from colic and constipation up to total blindness, paralysis, convulsions and death. They are thus described by Dr J. T. Arlidge (Diseases of Occupations):—
The poison finds its way gradually into the whole mass of the circulating blood, and exerts its effects mainly on the nervous system, paralysing nerve-force and with it muscular power. Its victims become of a sallow-waxy hue; the functions of the stomach and bowels are deranged, appetite fails and painful colic with constipation supervenes. The loss of power is generally shown first in the fingers, hands and wrists, and the condition known as “wrist-drop” soon follows, rendering the victim useless for work. The palsy will extend to the shoulders, and after no long time to the legs also. Other organs frequently involved are the kidneys, the tissue of which becomes permanently damaged; whilst the sight is weakened or even lost.
Dr M‘Aldowie, senior physician to the North Staffordshire Infirmary, has stated that “in the pottery trade lead is very slow in producing serious effects compared with certain other industries.” In his experience the average period of working in lead before serious lesions manifest themselves is 18 years for females and 2212 years for males. But some individuals fall victims to the worst forms of plumbism after a few months’ or even weeks’ exposure to the danger. Young persons are more readily affected than those of mature age, and women more than men. In addition, there seems to be an element of personal susceptibility, the nature of which is not understood. Some persons “work in the lead” for twenty, forty or fifty years without the slightest ill effects; others have attacks whenever they are brought into contact with it. Possibly the difference is due to the general state of health; robust persons resist the poison successfully, those with impoverished blood and feeble constitution are mastered by it. Lead enters the body chiefly through the nose and mouth, being inspired in the form of dust or swallowed with food eaten with unwashed hands. It is very apt to get under the nails, and is possibly absorbed in this way through the skin. Personal care and cleanliness are therefore of the greatest importance. A factory surgeon of great experience in the English Potteries
