Part 13

In some kinds of German silver are found varying quantities of iron, manganese, tin, and very frequently lead, added for the purpose of changing the properties of the alloy or cheapening the cost of production. But all these metals have a detrimental rather than a beneficial effect upon the general character of the alloy, and especially lessen its power of resistance to the action of dilute acids, one of its most valuable properties. Lead makes it more fusible; tin acts somewhat as in bronze, making it denser and more resonant, and enabling it to take a higher polish. With iron or manganese the alloy is whiter, but it becomes at the same time more refractory and its tendency toward brittleness is increased.

«SUBSTITUTES FOR GERMAN SILVER.»

There are many formulas for alloys which claim to be substitutes for German silver; but no one of them has yet become an article of general commerce. It will be sufficient to note these materials briefly, giving the composition of the most important.

«Nickel Bronze.»—This is prepared by fusing together very highly purified nickel (99.5 per cent) with copper, tin, and zinc. A bronze is produced containing 20 per cent of nickel, light-colored and very hard.

«Bismuth Bronze.»—

I II III IV Copper 25.0 45.0 69.0 47.0 Nickel 24.0 32.5 10.0 30.9 Antimony 50.0 — — — Bismuth 1.0 1.0 1.0 0.1 Tin — 16.0 15.0 1.0 Zinc — 21.5 20.0 21.0 Aluminum — — 1.0 —

I is hard and very lustrous, suitable for lamp reflectors and axle bearings; II is hard, resonant, and not affected by sea water, for parts of ships, pipes, telegraph wires, and piano strings; III and IV are for cups, spoons, etc.

«Manganese Argentan.»—

Copper 52 to 50 parts Nickel 17 to 15 parts Zinc 5 to 10 parts Manganese 1 to 5 parts Copper, with 15 per cent phosphorus. 3 to 5 parts

Readily cast for objects of art.

«Aphtite.»—

Iron 66 parts Nickel 23 parts Tungsten 4 parts Copper 5 parts

«Arguzoid.»—

Copper 55.78 parts Zinc 23.198 parts Nickel 13.406 parts Tin 4.035 parts Lead 3.544 parts

Silver white, almost ductile, suited for artistic purposes. {71}

«Ferro-Argentan.»—

Copper 70.0 parts Nickel 20.0 parts Zinc 5.5 parts Cadmium 4.5 parts

Resembles silver; worked like German silver.

«Silver Bronze.»—Manganese, 18 per cent; aluminum, 1.2 per cent; silicium, 5 per cent; zinc, 13 per cent; copper, 67.5 per cent. The electric resistance of silver bronze is greater than that of German silver, hence it ought to be highly suitable for rheostats.

«Instrument Alloys.»—The following are suitable for physical and optical instruments, metallic mirrors, telescopes, etc.:

I.—Copper, 62 parts; tin, 33 parts; lead, 5 parts.

II.—Copper, 80; antimony, 11; lead, 9.

III.—Copper, 10; tin, 10; antimony, 10; lead, 40.

IV.—Copper, 30; tin, 50; silver, 2; arsenic, 1.

V.—Copper, 66; tin, 33.

VI.—Copper, 64; tin, 26.

VII.—Steel, 90; nickel, 10.

VIII.—Platinum, 60; copper, 40.

IX.—Platinum, 45; steel, 55.

X.—Platinum, 55; iron, 45.

XI.—Platinum, 15; steel, 85.

XII.—Platinum, 20; copper, 79; arsenic, 1.

XIII.—Platinum, 62; iron, 28; gold, 10.

XIV.—Gold, 48; zinc, 52.

XV.—Steel, 50; rhodium, 50.

XVI.—Platinum, 12; iridium, 88.

XVII.—Copper, 89.5; tin, 8.5; zinc, 2.

«LEAD ALLOYS.»

The following alloys, principally lead, are used for various purposes:

«Bibra Alloy.»—This contains 8 parts of bismuth, 9 of tin, and 38 to 40 of lead.

«Metallic Coffins.»—Tin, 40 parts; lead, 45 parts; copper, 15 parts.

«Plates for Engraving.»—I.—Lead, 84 parts; antimony, 16 parts.

II.—Lead, 86 parts; antimony, 14 parts.

III.—Lead, 87 parts; antimony, 12 parts; copper, 1 part.

IV.—Lead, 81 parts; antimony, 14 parts; tin, 5 parts.

V.—Lead, 73 parts; antimony, 17 parts; zinc, 10 parts.

VI.—Tin, 53 parts; lead, 43 parts; antimony, 4 parts.

Hard lead is made of lead, 84 parts; antimony, 16 parts.

«Sheet Metal Alloy.»—

Tin 35 parts Lead 250 parts Copper 2.5 parts Zinc 0.5 part

This alloy has a fine white color, and can be readily rolled into thin sheets. For that reason it is well adapted for lining tea chests and for the production of tobacco and chocolate wrappers. The copper and zinc are used in the form of fine shavings. The alloy should be immediately cast into thin plates, which can then be passed through rolls.

«MAGNETIC ALLOYS.»

Alloys which can be magnetized most strongly are composed of copper, manganese, and aluminum, the quantities of manganese and aluminum being proportional to their atomic weights (55.0 to 27.1, or about 2 to 1). The maximum magnetization increases rapidly with increase of manganese, but alloys containing much manganese are exceedingly brittle and cannot be wrought. The highest practicable proportion of manganese at present is 24 per cent.

These magnetic alloys were studied by Hensler, Haupt, and Starck, and Gumlich has recently examined them at the Physikalisch—technische Reichsanstalt, with very remarkable and interesting results.

The two alloys examined were composed as follows:

Alloy I.—Copper, 61.5 per cent; manganese, 23.5 per cent; aluminum, 15 per cent; lead, 0.1 per cent, with traces of iron and silicon.

Alloy II.—Copper, 67.7 per cent; manganese, 20.5 per cent; aluminum, 10.7 per cent; lead, 1.2 per cent, with traces of iron and silicon.

Alloy II could be worked without difficulty, but alloy I was so brittle that it broke under the hammer. A bar 7 inches long and 1⁠/⁠4 inch thick was obtained by grinding. This broke in two during the measurements, but, fortunately, without invalidating them. Such a material is evidently unsuited to practical uses.

The behavior of magnetic alloys at high temperatures is very peculiar. Alloy I is indifferent to temperature changes, which scarcely affect its magnetic properties, but the behavior of alloy II is very different. Prolonged heating to 230° F. produces a great increase in its capability of magnetization, which, after 544 hours’ heating, rises from 1.9 to 3.2 kilogauss, {72} approaching the strength of alloy I. But when alloy II is heated to 329° F., its capability of magnetization fails again and the material suffers permanent injury, which can be partly, but not wholly, cured by prolonged heating.

Another singular phenomenon was exhibited by both of these alloys. When a bar of iron is magnetized by an electric current, it acquires its full magnetic strength almost instantaneously on the closure of the circuit. The magnetic alloys, on the contrary, do not attain their full magnetization for several minutes. In some of the experiments a gradual increase was observed even after the current had been flowing five minutes.

In magnetic strength alloy I proved far superior to alloy II, which contained smaller proportions of manganese and aluminum. Alloy I showed magnetic strengths up to 4.5 kilogauss, while the highest magnetization obtained with alloy II was only 1.9 kilogauss. But even alloy II may be called strongly magnetic, for its maximum magnetization is about one-tenth that of good wrought iron (18 to 20 kilogauss), or one-sixth that of cast iron (10 to 12 kilogauss). Alloy I is nearly equal in magnetic properties to nickel, which can be magnetized up to about 5 kilogauss.

«MANGANESE ALLOYS:»

«Manganese bronze» is a bronze deprived of its oxide by an admixture of manganese. The manganese is used as copper manganese containing 10 to 30 per cent manganese and added to the bronze to the amount of 0.5 to 2 per cent.

«Manganese Copper.»—The alloys of copper with manganese have a beautiful silvery color, considerable ductility, great hardness and tenacity, and are more readily fusible than ordinary bronze. A special characteristic is that they exactly fill out the molds, without the formation of blowholes, and present no difficulties in casting.

Cupromanganese is suitable for many purposes for which nothing else but bronze can advantageously be used, and the cost of its production is no greater than that of genuine bronze. In preparing the alloy, the copper is used in the form of fine grains, obtained by pouring melted copper into cold water. These copper grains are mixed with the dry oxide of manganese, and the mixture put into a crucible holding about 66 pounds. Enough space must be left in the crucible to allow a thick cover of charcoal, as the manganese oxidizes easily. The crucible is placed in a well-drawing wind furnace and subjected to a strong white heat. The oxide of manganese is completely reduced to manganese, which at once combines with the copper to form an alloy. In order to prevent, as far as possible, the access of air to the fusing mass, it is advisable to cover the crucible with a lid which has an aperture in the center for the escape of the carbonic oxide formed during the reduction.

When the reduction is complete and the metals fused, the lid is removed and the contents of the crucible stirred with an iron rod, in order to make the alloy as homogeneous as possible. By repeated remelting of the cupromanganese a considerable quantity of the manganese is reconverted into oxide; it is, therefore, advisable to make the casts directly from the crucible. When poured out, the alloy rapidly solidifies, and resembles in appearance good German silver. Another reason for avoiding remelting is that the crucible is strongly attacked by the cupromanganese, and can be used but a few times.

The best kinds of cupromanganese contain between 10 and 30 per cent of manganese. They have a beautiful white color, are hard, tougher than copper, and can be worked under the hammer or with rolls. Some varieties of cupromanganese which are especially valuable for technical purposes are given below:

I II III IV Copper 75 60 65 60 Manganese 25 25 20 20 Zinc — 15 5 — Tin — — — 10 Nickel — — 10 10

«Manganin.»—This is an alloy of copper, nickel, and manganese for electric resistances.

«MIRROR ALLOYS:»

«Amalgams for Mirrors.»—I.—Tin, 70 parts; mercury, 30 parts.

II.—For curved mirrors. Tin, 1 part; lead, 1 part; bismuth, 1 part; mercury, 9 parts.

III.—For glass balls. Tin, 80 parts; mercury, 20 parts.

IV.—Metallic cement. Copper, 30 parts; mercury, 70 parts.

V.—Mirror metal.—Copper, 100 parts; tin, 50 parts; Chinese copper, 8 parts; lead, 1 part; antimony, 1 part.

«Reflector Metals.»—I.—(Cooper’s.) Copper, 35 parts; platinum, 6; zinc, 2; tin, 16.5; arsenic, 1. On account of the hardness of this alloy, it takes a very high polish; it is impervious to the effects of the weather, and is therefore remarkably {73} well adapted to the manufacture of mirrors for fine optical instruments.

II.—(Duppler’s.) Zinc, 20 parts; silver, 80 parts.

III.—Copper, 66.22 parts; tin, 33.11 parts; arsenic, 0.67 part.

IV.—Copper, 64 parts; tin, 32 parts; arsenic, 4 parts.

V.—Copper, 82.18 parts; lead, 9.22 parts; antimony, 8.60 parts.

VI.—(Little’s.) Copper, 69.01 parts; tin, 30.82 parts; zinc, 2.44 parts; arsenic, 1.83 parts.

«Speculum Metal.»—Alloys consisting of 2 parts of copper and 1 of tin can be very brilliantly polished, and will serve for mirrors. Good speculum metal should have a very fine-grained fracture, should be white and very hard, the highest degree of polish depending upon these qualities. A composition to meet these requirements must contain at least 35 to 36 per cent of copper. Attempts have frequently been made to increase the hardness of speculum metal by additions of nickel, antimony, and arsenic. With the exception of nickel, these substances have the effect of causing the metal to lose its high luster easily, any considerable quantity of arsenic in particular having this effect.

The real speculum metal seems to be a combination of the formula Cu_〈4〉Sn, composed of copper 68.21 per cent, tin 31.7. An alloy of this nature is sometimes separated from ordnance bronze by incorrect treatment, causing the so-called tin spots; but this has not the pure white color which distinguishes the speculum metal containing 31.5 per cent of tin. By increasing the percentage of copper the color gradually shades into yellow; with a larger amount of tin into blue. It is dangerous to increase the tin too much, as this changes the other properties of the alloy, and it becomes too brittle to be worked. Below is a table showing different compositions of speculum metal. The standard alloy is undoubtedly the best.

Copper Tin Zinc Arsenic Silver Standard alloy 68.21 31.7 — — — Otto’s alloy 68.5 31.5 — — — Richardson’s alloy 65.3 30.0 0.7 2. 2. Sollit’s alloy 64.6 31.3 4.1 Nickel — Chinese speculum metal 80.83 — — 8.5 Antimony Old Roman 63.39 19.05 — 17.29 Lead

«PALLADIUM ALLOYS.»

I.—An alloy of palladium 24 parts, gold 80, is white, hard as steel, unchangeable in the air, and can, like the other alloys of palladium, be used for dental purposes.

II.—Palladium 6 parts, gold 18, silver 11, and copper 13, gives a reddish-brown, hard, and very fine-grained alloy, suitable for the bearings of pivots in clock works.

The alloys of most of the other platinum metals, so called, are little used on account of their rarity and costliness. Iridium and rhodium give great hardness to steel, but the commercial rhodium and iridium steel, so called, frequently contains not a trace of either. The alloy of iridium with osmium has great hardness and resistance and is recommended for pivots, fine instruments, and points of ship compasses.

«Palladium Silver.»—This alloy, composed of 9 parts of palladium and 1 of silver, is used almost exclusively for dental purposes, and is well suited to the manufacture of artificial teeth, as it does not oxidize. An alloy even more frequently used than this consists of platinum 10 parts, palladium 8, and gold 6.

«Palladium Bearing Metal.»—This alloy is extremely hard, and is used instead of jewel bearings in watches. It is composed of palladium 24 parts, gold 72, silver 44, copper 92.

«PLATINUM ALLOYS.»

Platinum has usually been alloyed with silver in goldsmith’s work, 2 parts silver to 1 of platinum being taken to form the favorite “platinum silver.” The object has been to produce an alloy having a white appearance, which can be polished, and at the same time has a low melting point. In addition to this platinum alloy the following are well known:

I.—A mixture of 7 parts platinum with 3 parts iridium. This gives to platinum the hardness of steel, which can be still further increased by taking 4 parts of iridium.

II.—An alloy of 9 parts platinum and 1 part iridium is used by the French in the manufacture of measuring instruments of great resisting power.

Compounds of copper, nickel, cadmium, and tungsten are also used in the construction of parts of watches; the latter acquire considerable hardness without becoming magnetic or rusting like steel.

III.—For this purpose a compound of {74} 62.75 parts platinum, 18 parts copper, 1.25 parts cadmium, and 18 parts nickel is much recommended.

IV.—Very ductile platinum-copper alloys have also been made, e. g., the so-called Cooper gold, consisting of 3 parts platinum and 13 parts copper, which is almost equal to 18-carat gold in regard to color, finish, and ductility. If 4 per cent of platinum is taken, these latter alloys acquire a rose-red color, while a golden-yellow color can be produced by further adding from 1 to 2 per cent (in all 5 to 6 per cent) of platinum. The last-named alloy is extensively used for ornaments, likewise alloy V.

V.—Ten parts platinum, 60 parts nickel, and 220 parts brass, or 2 parts platinum, 1 part nickel and silver respectively, 2 parts brass, and 5 parts copper; this also gives a golden-yellow color.

VI.—For table utensils a favorite alloy is composed of 1 part platinum, 100 parts nickel, and 10 parts tin. Articles made of the latter alloy are impervious to atmospheric action and keep their polish for a long time. Pure white platinum alloys have for some time been used in dental work, and they have also proved serviceable for jewelry.

VII.—A mixture of 30 parts platinum, 10 parts gold, and 3 parts silver, or 7 parts platinum, 2 parts gold, and 3 parts silver.

VIII.—For enameled articles: Platinum, 35 parts; silver, 65 parts. First fuse the silver, then add the platinum in the spongy form. A good solder for this is platinum 80 parts, copper 20 parts.

IX.—For pens: Platinum, 4 parts; silver, 3 parts; copper, 1 part.

«Platinum Gold.»—Small quantities of platinum change the characteristics of gold in many respects. With a small percentage the color is noticeably lighter than that of pure gold, and the alloys are extremely elastic; alloys containing more than 20 per cent of platinum, however, almost entirely lose their elasticity. The melting point of the platinum-gold alloy is high, and alloys containing 70 per cent of platinum can be fused only in the flame of oxyhydrogen gas, like platinum itself. Alloys with a smaller percentage of platinum can be prepared in furnaces, but require the strongest white heat. In order to avoid the chance of an imperfect alloy from too low a temperature, it is always safer to fuse them with the oxyhydrogen flame. The alloys of platinum and gold have a somewhat limited application. Those which contain from 5 to 10 per cent of platinum are used for sheet and wire in the manufacture of artificial teeth.

«Platinum-Gold Alloys for Dental Purposes.»—

I II III Platinum 6 14 10 Gold 2 4 6 Silver 1 6 — Palladium — — 8

«Platinum Silver.»—An addition of platinum to silver makes it harder, but also more brittle, and changes the white color to gray. An alloy which contains only a very small percentage of platinum is noticeably darker in color than pure silver. Such alloys are prepared under the name of _platine au titre_, containing between 17 and 35 per cent of platinum. They are almost exclusively used for dental purposes.

«Imitation Platinum.»—I.—Brass, 100 parts; zinc, 65 parts.

II.—Brass, 120 parts; zinc, 75 parts.

III.—Copper, 5 parts; nickel, 4 parts; zinc, 1 1⁠/⁠2 parts; antimony, 1 part; lead, 1 part; iron, 1 part; tin, 1 part.

«Cooper’s Pen Metal.»—This alloy is especially well adapted to the manufacture of pens, on account of its great hardness, elasticity, and power of resistance to atmospheric influences, and would certainly have superseded steel if it were possible to produce it more cheaply than is the case. The compositions most frequently used for pen metal are copper 1 part, platinum 4, and silver 3; or, copper 21, platinum 50, and silver 36.

Pens have been manufactured, consisting of several sections, each of a different alloy, suited to the special purpose of the part. Thus, for instance, the sides of the pen are made of the elastic composition just described; the upper part is of an alloy of silver and platinum; and the point is made either of minute cut rubies or of an extremely hard alloy of osmium and iridium, joined to the body of the pen by melting in the flame of the oxyhydrogen blowpipe. The price of such pens, made of expensive materials and at the cost of great labor, is of course exceedingly high, but their excellent qualities repay the extra expense. They are not in the least affected by any kind of ink, are most durable, and can be used constantly for years without showing any signs of wear.

The great hardness and resistance to the atmosphere of Cooper’s alloys make them very suitable for manufacturing {75} mathematical instruments where great precision is required. It can scarcely be calculated how long a chronometer, for instance, whose wheels are constructed of this alloy, will run before showing any irregularities due to wear. In the construction of such instruments, the price of the material is not to be taken into account, since the cost of the labor in their manufacture so far exceeds this.

«PEWTER.»

This is an alloy of tin and lead only, or of tin with antimony and copper. The first is properly called pewter. Three varieties are known in trade:

I (Plate Pewter).—From tin, 79 per cent; antimony, 7 per cent; bismuth and copper, of each 2 per cent; fused together. Used to make plates, teapots, etc. Takes a fine polish.

II (Triple Pewter).—From tin, 79 per cent; antimony, 15 per cent; lead, 6 per cent; as the last. Used for minor articles, syringes, toys, etc.

III (Ley Pewter).—From tin, 80 per cent; lead, 20 per cent. Used for measures, inkstands, etc.

According to the report of a French commission, pewter containing more than 18 parts of lead to 82 parts of tin is unsafe for measures for wine and similar liquors, and, indeed, for any other utensils exposed to contact with food or beverages. The legal specific gravity of pewter in France is 7.764; if it be greater, it contains an excess of lead, and is liable to prove poisonous. The proportions of these metals may be approximately determined from the specific gravity; but correctly only by an assay for the purpose.

«SILVER ALLOYS:»

«Aluminum Silver.»—Aluminum and silver form beautiful white alloys which are considerably harder than pure aluminum, and take a very high polish. They have the advantage over copper alloys of being unchanged by exposure to the air, and of retaining their white color.

The properties of aluminum and silver alloys vary considerably according to the percentage of aluminum.

I.—An alloy of 100 parts of aluminum and 5 parts of silver is very similar to pure aluminum, but is harder and takes a finer polish.

II.—One hundred and sixty-nine parts of aluminum and 5 of silver make an elastic alloy, recommended for watch springs and dessert knives.

III.—An alloy of equal parts of silver and aluminum is as hard as bronze.

IV.—Five parts of aluminum and 1 part of silver make an alloy that is easily worked.

V.—Also aluminum, 3 parts, and silver, 1 part.

VI. Tiers-Argent.—This alloy is prepared chiefly in Paris, and used for the manufacture of various utensils. As indicated by its name (one-third silver), it consists of 33.33 parts of silver and 66.66 parts of aluminum. Its advantages over silver consist in its lower price and greater hardness; it can also be stamped and engraved more easily than the alloys of copper and silver.

VII.—This is a hard alloy which has been found very useful for the operating levers of certain machines, such as the spacing lever of a typewriter. The metal now generally used for this purpose by the various typewriter companies is “aluminum silver,” or “silver metal.” The proportions are given as follows:

Copper 57.00 Nickel 20.00 Zinc 20.00 Aluminum 3.00

This alloy when used on typewriting machines is nickel-plated for the sake of the first appearance, but so far as corrosion is concerned, nickeling is unnecessary. The alloy is stiff and strong and cannot be bent to any extent without breaking, especially if the percentage of aluminum is increased to 3.5 per cent; it casts free from pinholes and blowholes; the liquid metal completely fills the mold, giving sharp, clean castings, true to pattern; its cost is not greater than brass; its color is silver white, and its hardness makes it susceptible to a high polish.