The composition of different kinds of bronze is shown below :— For edge-tools : copper, 100 parte ; tin, 14 parts. When properly tempered, this alloy is capable of taking nearly as fine an edge as steel.
For gilding : (1) copper, 82 parts; zinc, 18 parts ; tin, 3 parts ; lead, 2 parte. (2) eopper, 83 parts; zinc, 17 parts ; tin, 2 parts; lead, 1 part.
For medals: (1) copper, 89 parts ; tin, 8 parts ; zinc, 3 parts. This alloy takes a sharp impres sion by stamping. (2) (Chandet) copper, 95 parts; tin, 4 or 5 parts.
For mortars : copper, 93 parts; lead, 5 parts ; tin, 2 parts.
For statuary: (1) copper, 88 parts ; tin, 9 parts ; zinc, 2 parts; lead, I part. (2) copper, 821 parts ; zinc, 10i parts ; tin, 5 parts ; load, 2 parts. Nearly the proportions of the celebrated statue of Louis XV. (3) copper, 90 parts; tin, 9 parts; lead, I part. (4) copper, 91 parts ; tin, 9 parts.
German Silver.—This alloy ie much used as a substitute for silver ; it is composed of copper, zinc and nickel. The proportions of the three metals are various ; when intended as a substitute for silver, they aro 50 parts copper, 25 parts zinc, and 25 parts nickel ; castings, such as candlesticks, ite., are made of an alloy containing 60 parts of copper, and 20 parts of each of the other two constituents. German silver is harder than silver, and susceptible of a high polish. lt is of a greyish-white colour ; fuses at a bright-red beat, the zinc being volatilized in the open air. The three metals, in a state of division and intimately mixed, may be melted together in a crucible, having copper at the top and bottom. The whole is covered with a coating of fine charcoal and etrongly heated in an air furnace with a strong draught. Or the copper and nickel may ho fire,t melted in the crucible, fragments of hot zinc being afterwards added. To aid the fusion of the nickel, the mixture should he well stirred. Lead is sometimes added, and also iron, for the purpose of whitening the alloy.
Actual analyses of various kinds of German silver show the following proportions:— (1) Copper, 50 parts ; nie.kel, 20 parts ; zinc, 30 parts. Very malleable, and takes a high polish.
(2) Copper, 50 parts ; nickel, 26 parte; zinc, 24 parts. Good imitation of silver.
(3) Copper, 41 parts ; nickel, 18 parts; zinc, 41 parts. Rather brittle.
(4) Copper, 50 parts ; nickel, 25 parts ; zinc, 25 parts. Good imitation of silver ; white and malleable.
(5) Copper, 60 parts; nickel, 25 parts; zinc, 20 parts. For rolling and wire ; very tough and malleable.
(6) Copper, 40i parts; nickel, 31} parts; iron, 21 parts ; zinc, 25i parts. Made from Hill burghausen ore; equal to best Chinese sample.
(7) Equal parts of copper and nickel. Recommended by Pelouze as being superior to any alloys containing zine.
(8) Copper, 55 parts ; nickel, 24 parts; zine,16 parts ; tin, 3 parts ; iron, 2 parts. White metal spoon, sold as German plate.
is, also an alloy of copper and tin, in the proportions of 8 or 9 parts of the former to 1 of the latter. It is a very tenacious metal, easily forged, and possesses a considerable amount of resistance; it is the metal of which large guns were formerly cast, whence the name. In order to make a perfectly uniform alloy, the melted metals should be cooled in the moulds as rapidly as possible. Gun-metal of the above composition has a specific gravity of 8.462; the weight of a oubie inch is 0.304 lb., and its tensile strength 15-2 tous to the square inch.
Muntz's alloy of copper and zinc. For rolling into sheets, the best proportions are 60 parts copper to 40 parts zinc; but for other purposes its composition is variable. It WM patented in 1832 by Muntz of Birmingham, and has since superseded copper for sheathing the bottoms of ships. The alloy is made in a reverberatory furnace, the copper being melted first and the zinc added afterwards. The fused mixture is run into clay-lined vessels and ladled from these, while still hot, into iron ingot-moulds. It is rolled into sheets or worked into bolts at a, red heat ; the sheets are subsequently "pickled" in weak sulphuric acid, and then washed with water.
Pewter.—Pewter is an alloy of lead and tin, containing sometimes copper, zinc, or antimony. There are three distinct kinds of English-made pewter, viz. (1) Plate pewter, used for dishes and plates, an alloy usually made without lead, and containing principally tin with small quantities of antimony, bismuth, and copper ; (2) Trifle pewter, employed for casting drinking vessels, &c., an alloy of 82 parts tin with 18 parts lead, and containing variable quantities of antimony ; and (3) Ley pewter, containing 4 parts tin and 1 part lead, employed for the larger wine measures. Owing to the poisonous nature of lead, which is apt to be dissolved by the acetic acid always present in beer, the French government has prohibited the use of an alloy containing more than 18 per cent. of lead ; if the lead be not in excess of this quantity, the tin seems to have the effect of neutralizing its poisonous properties. When made in the above proportions, pewter has a specific gravity of 7.8, so that any specimens of a higher specific gravity than this may be known to contain too high a per centage of the heavier metal. Pewter is a soft metal resembling tin, but duller and darker in colour. Plates and dishes are hammered out of the variety called plate pewter, but drinking vessels, &c., are always cast into moulds from the common variety.