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http://mysite.du.edu/~jcalvert/phys/tin.htm
The chief use of tin, by tonnage, was for years the manufacture of tin plate. This is thin sheet steel with a coating of tin only about 2.3 µm thick. The tin adheres strongly and uniformly to the steel, protecting it from attack. A typical tin plate alloy is 88 Sn, 7.5 Pb, 4 Cu, 0.5 Sb. Cans made of tinplate are used for food products, since the tin was not attacked by most foods in the absence of air
The Romans often dipped copper dishes into molten tin to give a better taste to the drinks taken with the tinned items.
The use of tin that was essential to the war effort was its use in alloys. It is in this use that there are few alternatives to tin. A large amount of tin is used in solders, of which it is the principal ingredient, typically 60 Sn 40 Pb.
For more information on solders, see Lead. Pewter is an alloy ranging from pure tin to 74 Sn, 20 Pb, 3 Cu, 3 Sb. Two popular alloys have 6 Sb, 2 Cu and 4 Sb, 2 Cu, with the rest tin, or tin and lead. Pure tin is rather too soft, and the alloy hardens it a little. It is an easily workable metal for pots, platters and plates, an inexpensive substitute for silver.
At the beginning of World War II, tin was not only widely used in tinplate, but as tinfoil and tin collapsible tubes as well. A common tinfoil alloy was 92 Sn, 8 Zn. Cigarettes, sweets and chewing gum came wrapped in tinfoil, while toothpaste was supplied in tin tubes.
Molten tin has been used to cast window glass, in the Pilkington float glass process. The glass is poured out on the hot tin, which gives it a smooth surface. Terne plate is a covering of tin and lead alloy, 75 Pb and 25 Sn a typical composition. The metal covered is usually heavy-gauge steel, not the thin strip used for tinplate. Lead gives good resistance against sulphuric acid. Tin plate can easily be given a coating of lead by hot dipping.
For low loads, the tin-based bearing alloys called "babbitt" are superior. Isaac Babbitt was the original patentee. A typical alloy is SAE10: 90 Sn, 5 Sb, 5 Cu. These alloys depend on the formation of an intermetallic compound SbSn which forms hard, antifriction "cuboids." Similar alloys are lead-based, such as SAE14: 80 Pb, 10 Sn, 10 Sb, or "white metal," 75 Pb, 19 Sb, 5 Sn, 1 Cu. The popular and inexpensive Magnolia Metal was 80 Pb, 15 Sb, 5 Sn, or 90 Pb, 10 Sb. The lead alloys can carry less load than tin babbitt, because they are softer.
Gutenberg's contribution was the process of making type of good quality and sufficient amount to be used in general printing. The method he chose was to cast the type in metal, using a carefully made die to stamp out the molds. The solution was type metal, an alloy of 62 Pb, 24 Sb and 14 Sn, that not only melted at a low temperature, but also expanded slightly on cooling, so that it would fill the molds accurately. It was also a hard alloy, so the type would stand up to repeated use. Linotype machines used an 85 Pb, 15 Sb, 5 Sn (or 82, 15, 3) alloy. Gutenberg's invention was the method of manufacturing type. From there it was an easy step to the printing that made books available to the general public.
Pewter is a soft alloy of tin that was used for pitchers, platters and pots, a sort of inexpensive silver that was easily shaped and worked. A traditional alloy was 80 Sn, 15 Pb, 5 Sb. The lead was added to reduce the cost of the metal, the antimony to harden it. If the lead content is objectionable, as it is if food is to be in contact with the pewter, lead-free pewter of 85 Sn, 15 Sb or 85 Sn, 6.8 Cu, 6 Bi, 1.7 Sb can be used.
Lead is sold as soft lead, 99.90% pure, common lead (lead that has been desilvered), 99.85% pure, and corroding lead (for paint), 99.94% pure. Hard lead is alloyed with 6%-18% antimony, which increases the strength of the lead. The addition of only 1% Sb or 3% Sn increases the strength by 50%. Hard lead is used for battery plates. Terne plate is heavy sheet steel coated with a lead-tin alloy. 75-25 and 50-50 Pb-Sn alloys are used.
There is no risk at all in handling lead metal. It cannot be absorbed through the skin or the respiratory tract. Dilute hydrochloric acid has little effect on it, so the lead would pass through the stomach before any damage was done. Eating lead is probably safe, but not encouraged. Carbonated water dissolves lead to some degree. Food and drink should never touch lead, since organic acids, such as acetic acid, may dissolve lead. Lead is, on the whole, very much less a hazard than mercury. It was made dangerous by its widespread use in paint and motor fuel, and that is now past.
Lead pipes were once used for household water. Lead pipe was easy to form by casting or extrusion, and easy to join by fusion. A mixture of litharge, glycerine and linseed oil made "plumber's cement" that could be used for joining pipes without heat. With hard water, a layer of sulphate or carbonate forms on the lead, and lead does not enter the water. With soft water, as from cisterns, this protective layer does not form, and a dangerous amount of lead can dissolve in the water. Since lead pipes were widely used in Roman times, some experts have concluded that they poisoned the populace rather generally. In fact, Vitruvius shows that the hazard was appreciated, and steps taken to reduce it.
Acute lead poisoning results from ingesting SOLUBLE lead compounds. The symptoms were called "painter's colic" since painters, covered with white lead, were at risk. The damage appears to be mainly to the nervous system, and the effects not as acute as those of mercury poisoning. Lead is an accumulative poison, building up until it reaches a toxic level. An antidote after swallowing a soluble lead salt is a stiff drink of epsom salts, MgSO4, which precipitates insoluble PbSO4.
The ore sample or material to be tested was reduced to a powder, and some form of lead was added, together with certain additions that handled known impurities. The cupel was heated in a furnace to fuse the lead, and the sample was stirred with a wooden stick, which added some carbon. In this step, any gold or silver in the sample dissolved in the liquid metal, separating it from matter that would not dissolve. The solubility of gold and silver in lead, and the insolubility of iron, copper and zinc is the basis of the process. This rejected matter was then discarded, and the metallic mass brought to a higher temperature by blowing the fire with bellows. This raised the temperature to the point where litharge, PbO, formed rapidly. The litharge was pulled out as it was formed, and finally only a metallic drop remained, which was the purified gold and silver.
This assay process was called cupellation, which separated the gold and silver from the usual adulterants. Unfortunately, it did not part the gold from the silver, which required other means. It did, however, reveal the content of precious metals, and the touchstone could then determine the relative amounts of gold and silver that were present, and through this the value of the sample.
Pure lead is easily obtained by reducing the litharge with carbon, as described above.
Low-melting alloys are about 50% bismuth, with various amounts of lead, tin and cadmium, depending on the melting point required. Rose's alloy, which melts at 100°C, is 50 Bi, 28 Pb, 22 Sn. Wood's alloy, melting at 71°C, is 50 Bi, 24 Pb, 14 Sn, 12 Cd, or 50 Bi, 25 Pb, 12.5 Sn, 12.5 Cd. Wood's alloy is used for casting teaspoons for entertainment purposes. These alloys can also be used as patterns for investment casting, and for hobby and modelling purposes.
Lead is used for bullets and shot, chiefly because of its high density. Shot alloys have been given as 99.8 Pb, 0.2 As, or 94 Pb, 6 Sb. The latter is the common antimonial hard lead, also used for battery plates. Lead was too expensive for use in cannonballs. A smooth-bore hand weapon uses a spherical bullet. Any other shape would tumble excessively and produce an inaccurate, short range shot. A musketeer often carried his own lead, crucible and bullet mold and made his own bullets over his campfire.
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