Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 4, 1802).djvu/418

384] fragrance, but a bitterish aromatic taste; both of which may be imparted to water.

The Zedoary is a warm stomachic, and has been recommended in dyspeptic cases, for relieving flatulency, and invigorating the nervous system. Such root may be advantageously used by artisans, as an excellent yellow colour: and it may likewise be employed in painting with water-colours. For this purpose, it is prepared in the following manner: Boil 1 oz. of the root in a quart of water, till the fluid have sufficiently imbibed the colouring matter, for communicating a yellow tinge to paper: it is then to be filtered through a linen cloth. The decoction may be evaporated or dried in shells; after which, it may again be diluted, and will easily spread with the pencil.  ZINC, or, is a semi-metal, naturally obtained in a state of combination with different minerals, in England, Hungary, and other parts of the globe: it is of a whitish colour, nearly resembling that of lead, though it does not so speedily tarnish.

Zinc melts a short time before ignition; but, when heated to redness in the open air, it is liable to combustion, and burns with a dazzling blaze; so that a loose white oxyd is precipitated, which is known under the name of flowers of zinc.

This crude semi-metal is of great utility in the arts. Combined with gold, in equal portions, it forms a hard, white compound, that admits of a fine polish, and may be advantageously manufactured into specula, for optical instruments.

Zinc and tin, melted together, produce a kind of pewter; and, as the former spreads more uniformly, while it is much harder, and less fusible than tin, it has been proposed as a substitute for the latter, in tinning copper-vessels.

Spelter and copper readily unite in the fire; provided the combustion of the former be carefully prevented during the process: in this state, it forms a metal, distinguished by the general name of yellow copper; but which is divided into several sorts, according to the respective proportions contained in the alloy. Thus, three parts of copper and one of zinc, constitute ;—five or six of the former, and one of the latter, afford .—Tombac is composed of a still larger proportion of copper to that of zinc: it is of a deeper red than pinchbeck, and bears the name of its inventor. Prince's Metal consists of a larger proportion of zinc than either of the preceding compositions.—Similor, or Manheim gold, resembles pinchbeck: it is manufactured into spurious leaf-gold, laces, and similar shewy articles.

Zinc is dissolved in all acids; though the sulphuric is most frequently employed; and, in the proportions stated, p. 275, of the present volume, it forms white.

An useful substitute for white-lead, in painting houses, has lately been discovered in zinc, by M. de. He directs this mineral to be calcined in a crucible, placed horizontally in the cavity usually made for retorts, in reverberatory furnaces. The oxyd thus obtained, is then to be washed in water, with a view to separate such particles as may not have been perfectly calcined; and, when it is reduced to powder, a small portion of