Page:The American Cyclopædia (1879) Volume X.djvu/252

 LEAD ters present, which also serve to maintain an elevated temperature. The Dutch white lead contains more oxide of lead and possesses more body than the French, but is said to have a greater tendency, when used as a paint with oil, to turn yellow on exposure. White lead is frequently adulterated with other substances, principally sulphate of baryta. As a pigment it has been to a considerable extent supplanted by oxide of zinc, which, though of less body, is cheaper and does not blacken when exposed to sulphuretted hydrogen. Protoxide of lead dissolves readily in acetic acid ; four salts may thus be formed with varying amounts of oxide of lead, namely, the normal, sesquibasic, tri- basic, and sexbasic acetate. The normal and tribasic acetates are of importance in chemis- try and in the arts. The former when crystal- lized is generally called sugar of lead ; the so- lution of this is used in medicine under the name of Goulard's water. The solutions of the acetate have a sweetish astringent taste, and absorb carbonic acid with avidity from the atmosphere ; acetic acid also dissolves me- tallic lead when there is free access of air. The chromates of lead may be formed by pre- cipitation of solutions of the acetate by a solu- tion of bichromate of potassa ; they are valu- able pigments. The neutral chromate has a beautiful lemon-yellow color ; the basic chro- mates are orange or red. Lead combines with great avidity with sulphur. Four sulphides are known to exist, of which only the protosul- phide is important ; it will be described further on in treating of lead ores. The best solvent for metallic lead is dilute nitric acid ; it is but feebly attacked by sulphuric or muriatic acids, owing to the formation of insoluble sulphate or chloride, which protects the metal from fur- ther action by the acid. Sulphuric acid is gen- erated in leaden chambers, and concentrated to a certain extent in leaden pans ; a small quan- tity of lead is always taken up in concentrating the acid, which may be precipitated by dilu- tion of the acid by water. Lead Poisoning. Nearly if not quite all the compounds of lead are poisonous. In cases of acute poisoning, where a large quantity of a lead salt has been accidentally or otherwise taken, there is a me- tallic taste in the mouth, burning pain in the stomach, nausea and vomiting, followed by prostration and death or by chronic symptoms resulting in convalescence. Cases of chronic poisoning are very common among those en- gaged in smelting and handling lead, and in the manufacture and use of its compounds. in red and white lead works, in the manufac- ture of glazed cards, in the preparation of ma- terials for making flint glass and glazing earth- enware, and in bleaching Brussels lace, which is beaten with white lead to whiten the fibre, are especially liable to the chronic form of lead poisoning. Workers in metallic lead, as plumb- ers, are much less liable to the disease. It is a disputed point whether lead poisoning ever results from working in lead mines ; it may be that the sulphide of lead is innocuous, while the more rarely occurring carbonate is occa- sionally the cause of the disease. The suscep- tibility to the effects of the poison varies great- ly in different persons. Some are able to fol- low their occupation as house painters or in manufactories of white lead without suffering materially, while an instance is on record where, after careful inquiry, a severe case of lead colic in a fishing-tackle maker could only be traced to his chewing bits of metallic lead, which he chipped off while engaged for a few days in making sinkers. Among artisans who use it in their work, lead is introduced into the system either by the air passages or by the digestive organs; it is inhaled in fine dust, or it is swallowed. In this way, carefully wash- ing the hands previous to meals is of great im- portance as a preservative from its effects. Lead is often introduced into the system acci- dentally or as an adulteration in the manufac- ture of various liquors. The old name of lead colic, colica Pictonum, colic of Poitou, arose from the prevalence of colic there produced by its use in the manufacture of wine. Devon- shire colic was traced by Sir George Baker to the use of lead in clarifying cider; the dry bellyache of the West Indies arose from its use in the distillation of rum. Many glazed articles of earthenware, when acted on by acids, give up the lead contained in their gla- zing. In Nos. 10 and 11 of the Medicinische Zeitung, published by the medical society of Prussia (1859), a case is cited of lead poison- ing produced by snuff, and upon an analysis of the snuff by Hockel it was found to contain 2 per cent, of lead. Snuff packed in lead foil always contains lead. The wrappings of lead foil when the package of snuff is first opened often exhibit an incrustation resembling mould, which is carbonate of lead. The lead foil is frequently tinned on one side ; but this proves to be a very insufficient protection, as it is often corroded through, and the workmen are sometimes so careless as to put the tinned sur- face outside. There are four distinct affections produced by lead : colic, arthralgia, paralysis, and brain disease or encephalopathy. Of these, colic is by far the most frequent, it having occurred in 1,217 of the 2,171 cases of Tan- querel des Planches (Traite des maladies de plomb, Paris, 1839), while arthralgia occurred in 755 cases, paralysis in 127, and encephalo- pathy in about 72. In chronic poisoning by lead, the skin is dry and of an unhealthy earthy color, the pulse is slow, the secretions generally are diminished, the bowels constipated, and the patient loses flesh and strength. When the gums are examined, a blue line is generally found on their free margin at its junction with the teeth, particularly the incisors ; occasion- ally the mucous membrane lining the lips and palate has the same bluish color. If the patient be now attacked by lead colic, he is conscious of a sensation of pain and sinking, which he