The preceding table gives some of the experimental results obtained with the testing machine at Friedrich-Wilhelmshütte on the crude cast ingots; the resistance is increased, as with copper, by rolling or hammering.
The manganese German silver consists of
| Copper | 70.00 |
| Manganese | 15.00 |
| Zinc | 15.00 |
But as this alloy often breaks in rolling, the preference is given to the following proportions:
| Copper | 80.00 |
| Manganese | 15.00 |
| Zinc | 5.00 |
This results in a white, ductile metal, which is easily worked and susceptible of receiving a beautiful polish, like the alloys of nickel, which it may in time completely replace.
The bronzes of manganese, tin, and zinc were perhaps the first upon which important investigations were made; they were obtained by adding to an alloy of copper, zinc, and tin (ordinary bronze) a definite quantity of the cupro-manganese of the type indicated above (Cu 70, Mn 30). By this means the resistance is increased fully nine per cent., probably in the same way as the copper, that is, by the deoxidizing effect of the manganese, as both the copper and the tin are always more or less oxidized in ordinary bronzes.
Manganese combines with tin just the same as it does with copper, and the proportion which is recommended as giving the highest resistances is three to six per cent. of cupro-manganese.
However, notwithstanding the use of cupro-manganese, the tin, as in ordinary bronzes, has a tendency to liquate in those portions of the mould which are the hottest, and which become solid the last, especially in the case of moulds having a great width.
From a series of experiments made at Isabelle Hütte, it has been found that the metal which has the greatest resisting qualities was obtained from