Alloys of Lead and Tin

Specific Heats of Solid Mixtures.—The specific heat of a homogeneous solid mixture of solid components is not usually additively composed of the specific heats of the latter. W. Spring (1886) found that the total heat capacity of alloys of lead and tin was always greater than the sum of those of the components, but above the melting-point the two were equal. A. Bogojawlensky and N. Winogradoff (1908) find, however, that the heat capacities of the isomorphous mixtures ... 

The word stannum (modern Latin for tin) is used by Latin writers of later ancient periods not to designate tin, but an alloy of lead and tin in varying proportions, practically our pewter. 

Cu 1-2 to 1-6, As 09 to 1-7.4 The addition of more than 1 per cent, of arsenic to alloys of lead and tin causes increased hardness and compressive strength but the toughness is diminished such alloys are useful for bearings to withstand high bearing pressure free from impact.8 Lead anodes containing arsenic (less than 0-5 per cent.) are used in the electrolytic preparation of zinc. 

Frequently, printed circuit boards are finished by deposition of an alloy of lead and tin, which facilitates soldering. 

By the time that the Romans came to Britain, iron and bronze were being used for weapons and tools copper for vessels and ornaments lead for pipes and coffins silver and bronze for coinage and gold, silver and tin for ornaments. A considerable number of Roman drinking vessels have been found made of pewter, which is an alloy of lead and tin. Even the Romans must have known something about lead poisoning as their superior quality pewter had a lower level of lead in the alloy 20% instead of the normal 50%. 

Among leaden articles belonging to the Roman period are pipes, coffins, cists, etc. The Romans also used articles of pewter (p. 211), at that time an alloy of lead and tin in the ratio of 1 to 4. Probably the two metals were deliberately mixed to produce the pewter, for the Romans were familiar with solder. It is possible, however, that pewter may have been produced in the first instance from a natural mixture of tin and lead ores, just as bronze resulted from a mixture of tin and copper ores (p. 91). Professor Louis has recorded such an occurrence m the Far East, where he found the Chinese smelting a natural mixture of lead and tin ores obtained by washing certain alluvials in the State of Patain in the northern part of the Malay Peninsula. 

When a liquid alloy of lead and tin is cooled through a eutectic point, the microstructure of the solid produced contains... 

Baume recognised seven kinds of affinity (i) of aggregation (cohesion), (ii) simple, (iii) compound (e.g. mercury added to an alloy of lead and tin), (iv) intermediate (e.g. acid added to marble and water), (v) of decomposition, (vi) reciprocal, (vii) double (of four bodies). 

Fig. 3.1. The phase diagram for the lead-tin alloy system. There ore three phases L - a liquid solution of lead and tin (Pb) - a solid solution of tin in lead and (Sn) - o solid solution of lead in tin. The diagram is divided up into six fields - three of them are single-phase, and three ore two-phose.

DEF. The diagram shows the equilibrium constitution for all the binary alloys that can be made of lead and tin, in all possible proportions, or, in short, for the lead-tin system. 

All soft solders are alloys composed mainly of lead and tin mixed in proportions that vary from as little as 30% lead (and 70% tin), to as much as 98% lead (and only 2% tin). The brazing metals are mostly alloys of copper or silver their composition, as well as that of other alloys used since antiquity for soldering, are listed in Table 48 (Zhadkevich 2004). 

The ions having five tin or lead atoms are prepared by the reaction of a solution containing sodium and the cryptand reacting with alloys of sodium and tin or lead, respectively. It should also be mentioned that numerous derivatives of these materials have been prepared that contain alkyl and other groups. 

It will be recalled that with the ancients and into the middle ages tho word stannum was generally used for an alloy of lend and tin or other alloys of lead, but not as at present for tin itself. 

Terne Plate. This is a sheet-steel product that is coated with an alloy of tin and lead. The coatings range from 50-50 mixtures of lead and tin to as low as 12% dn and 88% lead. Plate used for roofing normally is about 25% tin and 75% lead. In addition to roofing, terne plate is used in the manufacture of gasoline tanks for automotive vehicles, oil cans, and containers for solvents, resins, etc. 

The last-mentioned alloy, which is the eutectic mixture of lead and tin, is very convenient for many operations (see p. 210). When used in a pot of the type shown in Pig. 53 oxidation of the metal—a drawback attending the use of metal baths—is largely overcome. 

High temperatures may be obtained also with the aid of baths of fusible metal alloys, e.g. Woods metal - 4 parts of Bi, 2 parts of Pb, 1 part of Sn and 1 part of Cu - melts at 71 °C Rose s metal - 2 of Bi, 1 of Pb and 1 of Sn - has a melting point of 94 °C a eutectic mixture of lead and tin, composed of 37 parts of Pb and 63 parts of Sn, melts at 183 °C. Metal baths should not be used at temperatures much in excess of 350 °C owing to the rapid oxidation of the alloy. They have the advantage that they do not smoke or catch fire they are, however, solid at ordinary temperature and are usually too expensive for general use. It must be remembered that flasks or thermometers immersed in the molten metal must be removed before the metal is allowed to solidify. 

Six elemental metals are mentioned in the Old Testament (e.g., Numbers 31 22) gold (Hebrew zahav), silver (kesef, also the Biblical Hebrew word for money), copper (ne-chosheth, often translated into English as brass, which is an alloy of copper and zinc and may, in fact, not have been known in the time of Moses, or bronze, an alloy of copper and tin, which was known in the time of Moses), iron (barzel), tin (b deel), and lead (ofereth). The ancient Greeks also recognized mercury. About seventy-five elemental metals are now known. 

National Bureau of Standards (NBS) alloys with certified compositions were used as standards along with Centre Technique des Industries de la Fonderie (CTIF) standards. These standards cover a fairly wide range of tin and lead concentrations. When no standards were available that had compositions close to those of the coins, corrections for the effect of lead and tin contents were calculated on the basis of the presence of these elements in various standards. 

The first archaeoli cal record of bronze production in China comes from an Eifitou Culture (1700 B.C.) site in Henan, Shanxi, China [6]. Bronze is an alloy of copper and tin (althou in ancient China, lead was also fi equently used). The eailiest known Chinese bronze object is shown in Figure 1.4, uiiich has 92% copper and 7% tin. This wine cup displays the basic metalworking features of the Chinese Bronze Age, which are sharply different from Near Eastern and Western traditions. This alloy is not an accident but a deliberate choice and indicates that a complex metalluigical infiastructure was in place to mine the ores of both metals and then smelt each ore to its respective metals. 

There are two types of solders soft and hard. Soft solders usually consist of a mixture of lead and tin and the heat required to melt them is supplied by a soldering iron. Hard solders include brass (copper-zinc alloys) solders, silver solders, copper solders, nickel-silver solders, and solders for light alloys the heat to melt them is usually supplied by a blow torch. 

Solder, an alloy consisting of lead and tin, is used to join metals. 70% by mass of solder is lead. Find the amounts of lead and tin in 400 g of solder. 

Alloys of lead and thallium 2 are distinctive in that they have higher melting points than either component. The amount of thallium varies from 3 to 65 per cent. The alloy containing 10% thallium, 20% tin, and 70% lead is resistant to the corrosive action of mixtures of sulfuric, nitric, and hydrochloric acids. This alloy is especially recommended for use as anode for the electrolytic deposition of copper, in which its corrosion is less than one-fifth that of lead alone. 

---