Fusible metals

Alloys of tin are very important. Soft solder, type metal, fusible metal, pewter, bronze, bell metal. Babbitt metal. White metal, die casting alloy, and phosphor bronze are some of the... 

The above techniques are not satisfactory for solid sample containing light fractions that will be lost if exposed to ambient conditions of pressure and temperature. Samples like these can best be handled by cooling the sample and encapsulating them in small sealed metal—fusible alloy—containers (capsules) or glass capillaries. The metal must have a low melting point. 

A hard, grayish, brittle metal fusible witli difficulty obtained by reduction of its oxides by C at a white heat. It is not readily oxidized by cold, dry air but is superflctally oxidized when heated. It decomposes lihnmting H and dissolves in dilute acids. 

The element is a hard, yellow, very ductile, and malleable metal fusible at a red beat not sensiblv volatile. In drv air it is not altered, but is converted into CaH,0, in damp air decomposes H,0 bums when heated... 

With the great excess of carbon present in the small furnace it was unhkely that the small amount absorbed by the iron should be seen as of importance. Aristotle and many of his successors even up to the Middle Ages looked on steel as a purer sort of iron. It had come nearer the typically metallic state. Cast iron had arrived at this state, yet it was brittle and non-formable. But it had the properties most typical of a metal fusibility and castabihty. Even as late as 1783 Georges Louis Leclerc de BufFon (1707-1788) in France wrote that... 

These additives must thus be capable of decomposing under heat action by liberating the species that react with the moving metal or metals by creating an interphase more fusible than the metal itself. 

Before this treatment, the cassiterite content of the ore is increased by removing impurities such as clay, by washing and by roasting which drives off oxides of arsenic and sulphur. The crude tin obtained is often contaminated with iron and other metals. It is, therefore, remelted on an inclined hearth the easily fusible tin melts away, leaving behind the less fusible impurities. The molten tin is finally stirred to bring it into intimate contact with air. Any remaining metal impurities are thereby oxidised to form a scum tin dross ) on the surface and this can be skimmed off Very pure tin can be obtained by zone refining. 

Place 50 g. of o-chloronitrobenzene and 75 g. of clean dry sand in a 250 ml. flask equipped with a mechanical stirrer. Heat the mixture in an oil or fusible metal bath to 215-225° and add, during 40 minutes, 50 g. of copper bronze or, better, of activated copper bronze (Section 11,50, 4) (1), Maintain the temperature at 215-225° for a further 90 minutes and stir continuously. Pour the hot mixture into a Pyrex beaker containing 125 g. of sand and stir until small lumps are formed if the reaction mixture is allowed to cool in the flask, it will set to a hard mass, which can only be removed by breaking the flask. Break up the small lumps by powdering in a mortar, and boil them for 10 minutes with two 400 ml. 

Place 150 g. of benzoic acid, 150 g. (139 ml.) of acetic anhydride and 0-2 ml. of syrupy phosphoric acid in a 500 ml. bolt-head flask. Fit the latter with a two-holed stopper carrying a dropping funnel and an efficient fractionating column (compare Fig. 7/7, 61, 1) it is advisable to lag the latter with asbestos cloth. Set up the flask in an oil bath or in a fusible metal bath. Distil the mixture very slowly and at such a rate that the temperature of the vapour at the head of the column does... 

As a general rule flasks and similar vessels should be heated in an air bath (compare Fig. II, 5, 3). A glycerol bath may be employed for temperatures up to 140° the glycerol is subsequently removed from the outside of the vessel by washing with water. Medicinal liquid paraffin may be used for temperatures up to about 220° hard hydrogenated cotton seed oil, Silicone fluids or fusible metal may be employed when higher temperatures are required. Small test-tubes and centrifuge tubes... 

Acetylene cylinders are fitted with safety devices to release the acetylene ia the event of fire. Cylinders manufactured ia the United States are equipped with safety devices which contain a fusible metal that melts at 100°C. In large cylinders the safety devices are ia the form of a replaceable, threaded steel plug with a core of fusible metal. Small cylinders (0.28 and 1.12 m 10 and 40 fT, respectively) may have the fusible metal ia passages ia the cylinder valve. 

Iron Precipitation. Rich sulfide ore or Hquated antimony sulfide (cmde antimony) is reduced to metal by iron precipitation. This process, consisting essentially of heating molten antimony sulfide ia cmcibles with slightly more than the theoretical amount of fine iron scrap, depends on the abihty of iron to displace antimony from molten antimony sulfide. Sodium sulfate and carbon are added to produce sodium sulfide, or salt is added to form a light fusible matte with iron sulfide and to faciHtate separation of the metal. Because the metal so formed contains considerable iron and some sulfur, a second fusion with some Hquated antimony sulfide and salt foHows for purification. 

Until 1930, approximately 90% of bismuth usage was for pharmaceutical appHcations (9). From that point until the 1970s, research produced new appHcations that greatiy expanded the uses of the metal. At that point the pharmaceutical use accounted for about 50% of the total bismuth consumption. By 1991, the fusible alloy category along with the other subdivisions each accounted for about 10% of the bismuth usage. Pharmaceutical usage was down to 20%. 

LB = lens blocking W = work holding RS = radiation shielding FSD = fusible safety device PC = proof casting SMF = sheet metal forming ... 

Low viscosity cellulose propionate butyrate esters containing 3—5% butyryl, 40—50% propionyl, and 2—3% hydroxyl groups have excellent compatibihty with oil-modified alkyd resins (qv) and are used in wood furniture coatings (155). Acetate butyrate esters have been used in such varied apphcations as hot-melt adhesive formulations (156), electrostatically spray-coated powders for fusible, non-cratering coatings on metal surfaces (157—159), contact lenses (qv) with improved oxygen permeabiUty and excellent wear characteristics (160—162), and as reverse-osmosis membranes for desalination of water (163). 

Figure 9.1 illustrates the rise in eylinder pressure with temperature. Normally, aeetylene eylinders are fitted with a fusible metal plug whieh melts at about 100°C. 

The effect of temperature on vapour pressure is shown in Figure 9.3. Cylinders are normally protected from over-pressurization by a fusible metal plug melting at about 85°C. 

W orld annual production of bismuth and its compounds has hovered around 4000 tonnes of contained Bi for many years and a similar amount of secondary (refinery) Bi is also produced. Production has been dominated by China, Japan, Peru, Bolivia, Mexico, Canada, USA and Australia which, between them, account for almost of all supplies. Prices tor die free element have fluctuated wildly since the 1970s, from < 4 (Xl/kg to > 44.00/kg at die end of 1990 it was 6.30/kg Consumption of the metal and its compounds has also been unusual, usage in the USA dropping by a factor of 2 from 1973 to 1975, for example. The mam uses are in pharmaceuticals, fusible alloys (including type metal, p. 547), and metallurgical additives. 

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