Читать книгу Henley's Formulas, Recipes and Processes (Applied Chemistry) - Various - Страница 179
Britannia Metal.
ОглавлениеBritannia metal is an alloy consisting principally of tin and antimony. Many varieties contain only these two metals, and may be considered simply as tin hardened with antimony, while others contain, in addition, certain quantities of copper, sometimes lead, and occasionally, though rarely on account of its cost, bismuth. Britannia metal is always of a silvery-white color, with a bluish tinge, and its hardness makes it capable of taking a high polish, which is not lost through exposure to the air. Ninety per cent of tin and 10 per cent of antimony gives a composition which is the best for many purposes, especially for casting, as it fills out the molds well, and is readily fusible. In some cases, where articles made from it are to be subjected to constant wear, a harder alloy is required. In the proportions given above, the metal is indeed much harder than tin, but would still soon give way under usage.
A table is appended, giving the composition of some of the varieties of Britannia metal and their special names.
| Tin | Antimony | Copper | Zinc | Lead | |
|---|---|---|---|---|---|
| English | 81.90 | 16.25 | 1.84 | — | — |
| English | 90.62 | 7.81 | 1.46 | — | — |
| English | 90.1 | 6.3 | 3.1 | 0.5 | — |
| English | 85.4 | 9.66 | 0.81 | 3.06 | — |
| Pewter | 81.2 | 5.7 | 1.60 | — | 11.5 |
| Pewter | 89.3 | 7.6 | 1.8 | — | 1.8 |
| Tutania | 91.4 | — | 0.7 | 0.3 | 7.6 |
| Queen’s metal | 88.5 | 7.1 | 3.5 | 0.9 | — |
| German | 72.0 | 24.0 | 4.0 | — | — |
| German | 84.0 | 9.0 | 2.0 | 5.0 | — |
| German (for casting) | 20.0 | 64.0 | 10.0 | 6.0 | — |
| Malleable (for casting) | 48.0 | — | 3.0 | 48.0 | 1.0 |
Britannia metal is prepared by melting the copper alone first, then adding a part of the tin and the whole of the antimony. The heat can then be quickly moderated, as the melting point of the new alloy is much lower than that of copper. Finally, the rest of the tin is added, and the mixture stirred constantly for some time to make it thoroughly homogeneous.
An alloy which bears a resemblance to Britannia metal is Ashberry metal, for which there are two formulas.
| I | II | |
|---|---|---|
| Copper | 2 | 3 |
| Tin | 8 | 79 |
| Antimony | 14 | 15 |
| Zinc | 1 | 2 |
| Nickel | 2 | 1 |
