I

A mixture of 7 parts platinum with 3 parts iridium. This gives to platinum the hardnessof 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 themanufacture of measuring instruments of great resisting power.

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

III

For this purpose a compound of

62.75 parts platinum, 18 parts copper, 1.25 parts cadmium, and 18 parts nickel is muchrecommended.

IV. — Very ductile platinum-copper alloyshave also been made, e. g., the so-called Cooper gold, consisting of 3 parts platinum and13 parts copper, which is almost equal to 18-carat gold in regard to color, finish, andductility. If 4 per cent of platinum is taken, these latter alloys acquire a rose-redcolor, 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 forornaments, 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 partscopper; 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 actionand keep their polish for a long time. Pure white platinum alloys have for some time beenused 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.