I fused various proportions of tin and lead together, as per the following table, in order to find some of the more prominent characteristics of the several alloys. The specific gravity of the tin was 7.2, that of the lead was 11.23; and the portions taken were such as to combine, 1, 2, or more atoms of tin with 1 of lead. The several metals were melted and the compounds formed under a few drops of tallow, otherwise the oxidation is so rapid that the proportions are disturbed and the quantity of pure alloy is not equal to the weight of the ingredients. Without this precaution it is no uncommon occurrence in small experiments to obtain only 3 parts of fusible alloy from 4 of metal.
| Atoms. | Weights | Sp. Gr. by calculation. | Sp. Gr. by experim. | Fusing Point. | ||||
|---|---|---|---|---|---|---|---|---|
| Tin. | Lead. | Tin. | Lead. | |||||
| 1 | + | 1 | .58 | + | 1 | 9.32 | 9.17 | 430° |
| 2 | + | 1 | 1.16 | + | 1 | 8.64 | 8.79 | 350 |
| 3 | + | 1 | 1.73 | + | 1 | 8.25 | 8.49 | 340 |
| 4 | + | 1 | 2.3 | + | 1 | 8.00 | 8.10 | 345 |
| 5 | + | 1 | 2.9 | + | 1 | 7.93 | 8.00 | 350 |
| 6 | + | 1 | 3.47 | + | 1 | 7.81 | 7.90 | 360 |
From the above table it appears that when 1 atom of tin is united to 1 of lead there is an expansion of volume; but when more than 1 of tin are combined to 1 of lead there is a contraction of volume, or the density is above that by calculation. This increase of density is greatest when 3 atoms of tin are combined with 1 of lead; and it is not improbable the tenacity may then be a maximum; though Muschenbroek finds it more tenacious when 3 parts tin are united to 1 of lead, which answers more nearly to 4 atoms tin and 1 of lead; this opinion is countenanced by the fact that tin is much the most tenacious of the two metals taken singly.
It is remarkable that the fusing point of these alloys is below those of either tin or lead. The lowest of all (340°) is when 3 atoms of tin are alloyed with 1 of lead.
Common pewter, I find, is an alloy of 4 atoms of tin and 1 of lead nearly, and fuses about 345 or 350°. This is perhaps the best proportion; it is hard, tenacious and of a good colour. More of lead would impair the colour, and more of tin would impair the tenacity and increase the expence, though it might improve the colour.
Certain articles for family use, such as tea-pots, spoons, &c. are made of white metal, which commonly, though I apprehend improperly, goes by the name of tutenag. This metal in colour approaches more to silver than pewter does. A spoon of this description I found to be pure tin.
2. Tin and zinc. This alloy is easily made by fusion. The metals seem to unite in any proportion. I melted together 29 parts zinc and 52 tin (1 atom of each), and obtained a white hard alloy of about 6.8 specific gravity. When 2 atoms tin and 1 zinc are united the specific gravity is 6.77, which is below the mean. The alloy appears to be very hard and tenacious; and probably might be put to some use.
3. Tin and bismuth. These metals readily combine by fusion in any proportion. When 52 parts tin and 62 bismuth are fused together (1 atom to 1), a fine, smooth, hard but brittle alloy is obtained of the specific gravity 8.42. It fuses at 260°. Two atoms tin and 1 bismuth give an alloy of 8 specific gravity, which fuses about 320°. The alloy of 1 atom tin and 2 of bismuth is of 8.67 specific gravity, and fuses about 260°. The alloy of 3 atoms tin and 1 bismuth is of 7.73 specific gravity, and fuses at 350°. The alloy of 1 atom tin and 3 bismuth is of specific gravity 9.14, and fuses at 330°.
4. Tin with antimony. This compound is said to be white and brittle when formed of equal parts. I did not succeed in uniting the two metals by fusion on a small scale.
5. Tin with arsenic. When 15 parts of tin and 1 of arsenic are fused together the alloy crystallizes in large plates like bismuth, according to Bayen. It is brittle and less fusible than tin. This alloy must be composed of 5 atoms of tin and 1 of arsenic, that is, 312 tin and 21 arsenic.