Alloy arsenic-lead

Phosphorized deoxidized arsenical copper (alloy 142 (23)) is used for heat exchangers and condenser tubes. Copper-arsenical leaded Muntz metal (alloy 366), Admiralty brass (alloy 443), naval brass (alloy 465), and aluminum brass (alloy 687), all find use in condensers, evaporators, ferrules, and heat exchanger and distillation tubes. The composition of these alloys is Hsted in Table 5. 

Lead and Alloys Chemical leads of 99.9 percent purity are used primarily in the chemical industry in environments that form thin, insoluble, and self-repairable protective films, e.g., salts such as sulfates, carbonates, or phosphates. More soluble films such as nitrates, acetates, or chlorides offer little protection. Alloys of antimony, tin, and arsenic offer limited improvement in mechanical properties, but the usefulness of lead is limited primarily because of its poor structural qualities. It has a low melting point and tensile stress as low as 1 MPa (145 Ibf/in ). 

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. 

Arsenopyrite and loellingite are both arsenic minerals that can be smelted to produce elemental arsenic. Both elemental arsenic and arsenic trioxide (As203) are produced commercially the latter is the raw material for the production of numerous arsenic compounds. Elemental arsenic is used to make alloys with lead and copper. Arsenic compounds have a number of uses, including... 

Elemental arsenic is used in alloys of lead and copper, in semiconductors, and as an additive to the grid metal in storage batteries. Arsenic compounds have been used as pesticides and wood preservatives [4]. Although arsenic is most well known for its use as a poison, some evidence suggests that trace amounts may be essential for good health [5]. Inorganic forms of arsenic are more toxic than the organic forms arsenite, As (III), is the most toxic form of the element, followed by arsenate, As (V), monomethylarsenate, and dimethylarsenate. 

The Binary System Lead-Tin. The phase diagram for the lead-tin system of alloys is shown as Figure 24-5. This system rather closely resembles the system arsenic-lead, except for the fact that there is an appreciable solubility of tin in crystalline lead and a small solubility... 

Arsenic is used most commonly in the form of its compounds. A much smaller amount of the element itself is used in alloys. For example, certain parts of lead storage batteries used in cars and trucks contain alloys of lead and arsenic. Arsenic has also been used to make lead shot in the past. The amount of arsenic used in these applications is likely to continue to decrease. It is too easy for arsenic to get into the environment from such applications. 

Shot-met aL An alloy of lead, 56 paru> arsenic, 1. Used for making binl-shot. 

Arsenic is sometimes used in the manufacture of its compounds, but more often in alloys. Small quantities, o-i to o 2 per cent, are added to lead for the production of shot (p. 196). Arsenical lead anodes are used in the electrolytic production of zinc. Alloys with antimonial lead containing 1 to 2 per cent of arsenic and sometimes other elements are used for sheaths for electric cables, etc. Arsenical coppers and bronzes are used for high temperature work such as locomotive fireboxes, etc. 

One of the most common applications for these two metalloids is for use when strengthening alloys, or mbrtures of elements, especially lead. Lead is a relatively soft, dense metal, so to make lead harder for applications such as bullets, either metalloid can be added to help make the resulting product stronger. This practice of alloying arsenic and antimony with lead dates back to the Bronze Age. 

Also included in Lead Operations are a lead allo3rs plant, a copper products plant, and an effluent treatment plant. The lead alloys plant produces arsenic-lead and antimony-lead alloys from the treatment of softener slag and silver refinery baghouse dust. The copper products plant produces copper sulphate, copper arsenate and sodium antimonate fi"om the treatment of copper matte and refinery baghouse dusts. The effluent treatment plant treats effluents from the zinc and lead operations as well as surface runoff from throughout the metallurgical operation. 

The phase diagram for the lead-tin system of alloys is shown as Figure 17-6. This system rather closely resembles the system arsenic-lead, except that there is an appreciable solubility of tin in crystalline lead and a small solubility of lead in crystalline tin. The phase designated a is a solid solution of tin in lead, the solubility being 19.5 mass percent at the eutectic temperature and dropping to 2% at room temperature. The phase /8 is a solid solution of lead in tin, the solubility being about 2% at the eutectic temperature and extremely small at room temperature. The eutectic composition is about 62 mass percent tin, 38 mass percent lead. 

Cooling curves for samples of arsenic-lead alloys. 

Bullion commonly contains np to two per cent arsenic. Arsenic is preferentially oxidised in the softening or Harris processes, bnt more readily than antimony. Conseqnently when softener slag is reduced to form an antimonial lead alloy, arsenic can be retained in the residual slag from where it can be extracted by leaching and precipitation as arsenic trioxide or as calcium arsenite. Alternatively it can be extracted from canstic slags from the Harris process by leaching and precipitation with lime as calcium arsenite, which can contain around 20 per cent As. 

To be classified as a copper, an alloy must contain a minimum of 99.3% copper. Elements such as silver, arsenic, lead, phosphorus, antimony, tellurium, nickel, cadmium, sulfur, zirconium, manganese, boron, and bismuth may be present, singly or in combination. Because of the good electrical properties of copper, it is used primarily in electrical or electronic applications such as bus bars, waveguides, wires, switches, and transfer components. Because copper is a noble metal, it also finds many applications in corrosive environments. Table 18.4 gives the chemical composition of some of the coppers used in corrosion applications. 

The principal use of elemental arsenic is in its alloys with lead. 

The principal use of elemental arsenic is in its alloys with lead. Lead shot, formed by allowing drops of molten metal to fall through air, contains from... 

Crude lead contains traces of a number of metals. The desilvering of lead is considered later under silver (Chapter 14). Other metallic impurities are removed by remelting under controlled conditions when arsenic and antimony form a scum of lead(II) arsenate and antimonate on the surface while copper forms an infusible alloy which also takes up any sulphur, and also appears on the surface. The removal of bismuth, a valuable by-product, from lead is accomplished by making the crude lead the anode in an electrolytic bath consisting of a solution of lead in fluorosilicic acid. Gelatin is added so that a smooth coherent deposit of lead is obtained on the pure lead cathode when the current is passed. The impurities here (i.e. all other metals) form a sludge in the electrolytic bath and are not deposited on the cathode. 

---