or RED-LEAD, is a calx of lead of a vivid red colour, which colour it acquires by a slow calcination and reverberation. See CHEMISTRY, p. 1213.

The minium in commerce is chiefly brought from Holland, where large quantities of it are manufactured.

The method in which minium is made in large quantities with us is this—They first burn lead in a furnace into a kind of litharge, by continually stirring it while melted with an iron rake; this they afterwards grind with two pair of stones, which deliver it from one to another, the first pair grinding it coarser, the second finer; these are worked by means of a mill which moves six pair of them at once. When thus reduced to a fine powder, it is washed and then put into a furnace, and is burnt with a reverberatory fire for two or three days, all the while they continue stirring it with a large iron rake, hung on a swivel or iron hook; and toward the end of the time they watch its being of the right colour. When this is doing, the fire must not be carried beyond a certain degree, lest the matter clot and run together.

The process by which minium is prepared is described in the following manner by M. Jars*. The furnace is of the reverberatory kind, with two fire-places at the ends; each fire-place being separated from the area, or body of the furnace, by a wall twelve inches high. The fire-places are fifteen inches broad, and their length is equal to the breadth of the whole furnace, which is about eight or nine feet. The length of the area from one place to the other is nine or ten feet. The quantity of lead used in one operation is about 1500 pounds, of which nine parts are lead obtained from furnaces where the ore is smelted, and one part is lead extracted from the scoria which is formed in smelting the ore. This latter kind is said to be necessary, as the former could not alone be reduced into powder. All the lead is at once put into the area, the bottom of which is level. The calx, as fast as it is formed, is drawn to one side, by means of a rake suspended by a chain before the mouth of the furnace. In four or five hours the whole quantity of the lead is calcined, or, if any pieces remain uncalcined, they are separated, and kept for the next operation. The heat employed is that of a cherry-red, and the fire-places and mouth are kept open, that the air may accelerate the calcination. The powder or calx is to be frequently stirred to prevent its concreting; and when this operation has been continued about 24 hours, the matter is taken out of the furnace, and laid on a flat pavement. Then cold water is thrown on it, to give it weight, as the workmen say; but rather (as M. Jars thinks) to make it friable. It is then to be ground in a mill, and the finer part is separated by washing, while the coarser part, referred for some following operation, is to be placed at the mouth of the furnace in order to retain the melted lead. The fine powder, which is now of a yellow colour, is again put into the same or a similar furnace, and exposed to a very moderate fire, from 36 to 48 hours; during which time, it is stirred frequently to prevent its concreting; and the powder gradually acquires its proper red colour. The minium is then to be taken out of the furnace, cooled, and fitted through an iron sieve placed in a caulk.

The bright colour of minium might render it valuable in painting, if it could stand with certainty in either oil or water. But as it is subject to become black, it cannot be safely trusted, except in hard varnishes; and is, therefore, seldom used in oil, or even in water, unless for very gross purposes, or as a ground for vermilion. The goodness of minium may be distinguished by the brightness of its colour; and the adulteration to which it is liable may be detected by putting an ounce of it into a crucible with an equal quantity of charcoal dust, well mixed together, and placing the crucible in a common fire sufficient to melt lead, which is to be covered with another small crucible inverted into it. When it has been continued for some time on the fire, take it out and strike it against against the ground. The minium will thus be reduced to its metallic state; and its diminished weight, when freed from the charcoal dust and cold, will indicate the proportion of adulterated matter. Minium is also used as a flux in forming the enamel for grounds, and in glazing, &c.

In medicine, minium is used as an external application. It obtunds the acrimony of the humours, allays inflammations, and is excellent in the cleansing and healing of old ulcers: It is used on these occasions in many of the plasters and ointments of the shops. It was an ingredient in the official composition called *implastrum deminio*, employed as a desiccative and cicatrizer; but now diluted for that made in the same manner with litharge, because it does not stick so well, and is more difficult of preparation.