Lead is mentioned in the Sacred Writings; and is described by Homer as in common use at the period of the Trojan war. The ancients seem to have considered it as nearly allied to tin. The Romans employed it to sheathe the bottoms of their ships, fastening it to the planks and timbers by nails made of bronze.
When first melted, lead is bright, but it soon tarnishes by exposure to the air. It melts at a temperature very low in comparison with most other metals; and when a strong heat is applied, it boils and evaporates.
Lead is much employed in the useful arts. When rolled between iron cylinders to a requisite state of thinness and uniformity, it is used for the covering of houses and churches, notwithstanding the danger, in case of fire, to persons within, who are exposed to a shower of burning metal. It is cast into pipes, cisterns, and reservoirs for water, as well as into large boilers for chemical purposes. But all culinary or domestic vessels made of lead, particularly if intended for the keeping of acid liquors, should carefully be avoided, as the surface of the lead is thereby corroded, and the liquid contained in them is rendered poisonous. Hence arises that dreadful complaint, too well known where cyder is kept in leaden cisterns, called the Devonshire colic; hence also the injury which sometimes follows from the use of lead in the glazing of coarse earthenware.
Great quantities of lead are consumed for the making of shot. For this purpose the metal is alloyed with arsenic ([242]), to render it more brittle; and to render the grains more round and perfect than they otherwise would be. Shot is formed by dropping the melted alloy into water, through an iron or copper frame, perforated with round holes, according to the size required. For the smallest shot the elevation is about ten feet above the water; and for the largest about a hundred and fifty feet.
An alloy of lead and tin, in the proportion of two parts of lead and one of tin, forms the solder which is used by plumbers. The types that are used by printers for very large characters are sometimes composed of an alloy of lead and copper. Lead is also used, with tin, in the manufacture of pewter.
Oxides of Lead.
The different oxides ([21]) of lead are easily soluble in oil, and consequently are of great use to painters. Of these the following are the most important:
White Lead, or Ceruse.—This is made by suspending thin plates of lead over heated vinegar, in such manner that the vapour which rises from the acid may circulate about the plates. By this process the plates become at length entirely corroded, and converted into a heavy white powder. The manufacture of white lead is a most unhealthy trade, and is confined to a few persons, who have large conveniences for the purpose. This substance, when mixed with oil, is used as a paint for wood-work both of the outsides and insides of buildings. The fumes that are emitted from white paint are extremely noxious. Persons who breathe them are frequently seized with pains, and experience symptoms not much unlike those that precede palsy; and the danger which attends the inhabiting of apartments recently painted is well known. The odour of vinegar will correct the pernicious effect of these exhalations, by acting as a solvent, and combining with, and precipitating them. We are informed that white lead, dangerous as it is, was in great request among the Roman ladies as a cosmetic. It is sometimes used as an external application for ulcers and other kinds of sores.
Massicot is a mineral substance of yellow colour, used for painting, and prepared from the dross or pellicle that is formed by the melting of lead.
Red Lead, or Minium, is a mineral substance of red colour, used for painting, and made, by a tedious and troublesome process, from massicot. For this purpose the massicot is ground to a fine powder, put into a furnace, and constantly stirred, whilst the flame of the burning coals plays against its surface for about forty-eight hours, when it is converted into a red powder, which is the article under consideration. It is subsequently passed through very fine iron sieves. The use of red lead as a pigment is well known; but as it is liable to turn black, vermilion is generally preferred to it. It is sometimes employed in medicine as an external application for abating inflammations, for cleansing and healing ulcers, and the like; and is used in the manufacture of glass.