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.
Mirror Alloys:
Amalgams For Mirrors.
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.