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.