Alloys of Lead with other Metals.
1. Lead and zinc. These two metals seem to have a weak affinity. They are easily united, or rather mixed, in any proportion by fusion under a little tallow. But however they may be mixed there is a strong tendency to separate again, which no doubt is occasioned in part by their great difference in specific gravity.
I have fused lead and zinc together in various proportions, from 6 parts lead to 1 of zinc, to 1 part lead to 2 of zinc. The compound usually gives a specific gravity rather greater than the mean; but upon being broken the fracture is often like that of zinc in one part and not so in another; and the analysis of fragments proves that a great difference exists in their composition. Subsequent fusion sometimes improves the combination and at other times the contrary. Six parts lead and 1 of tin gave a compound as nearly uniform as any. It was 11 specific gravity, harder and whiter than lead and had much the appearance of pewter, that is, the alloy of tin and lead.
2. Lead and bismuth. These metals alloy well. Three parts lead and 2 of bismuth unite by fusion and form a tenacious alloy which fuses about 340°. Muschenbroek found it ten times stronger than lead. It grows dark coloured soon by keeping. Its specific gravity by my observation is 10.85, which is rather greater than the mean. It is constituted of 1 atom of each metal, or 62 bismuth to 90 lead.
Three parts lead and 4 bismuth (1 atom lead to 2 bismuth) fuses at 250°. This is the lowest temperature at which any alloy of two metals fuses. With a little tin it makes the triple alloy which fuses lower than any other metallic compound, without mercury, as will be shown in the sequel. The specific gravity of this alloy of lead and bismuth is 10.7, which is greater than the mean.
The alloy of 1 part lead and 2 bismuth (1 atom of lead and 3 bismuth), fuses at 280°, and is of 10.1 specific gravity, or rather less than the mean.
The alloy of three parts lead and 1 bismuth (2 atoms of lead and 1 of bismuth) fuses at 450°. The specific gravity is 11, or rather greater than the mean.
3. Lead and antimony. These two metals combine by fusion in any proportion. The alloy is of a fine grain and is brittle or flexible as the antimony or lead prevails. The principal use of this alloy, I believe, is in the formation of printers’ types. The small types require a harder alloy or one with more antimony; the large types have a greater share of lead as being less expensive. On examination of the different types I find 3 proportions of the alloy principally in use. The smallest types are cast from a mixture which very nearly corresponds with 40 parts of antimony to 90 of lead (or 1 atom to 1). It is hard, has a fracture like steel and is of the specific gravity 9.4 or 9.5 nearly, and fuses about 480 or 500°. The proportions were determined both by analysis and by inference from the specific gravity of the metal.
The middle sized types are made of metal composed of 1 atom of antimony and 2 of lead, or 40 parts antimony and 180 of lead. This alloy fuses about 450° or 460° and has the specific gravity of 10 nearly.
The largest types or letters of 2 or 3 inches diameter are made of metal composed of 1 atom antimony and 3 of lead, or 40 parts to 270. This alloy also fuses about 450 or 460°, which is a very remarkable fact. Its specific gravity is usually 10.22. After several trials I could not determine whether the fusing point of this or the preceding alloy was lower; and equal parts of the two alloys fused together were liquified at the same temperature of 450 or 460°.