Of lead metal

The cmde lead and discard slag from the reduction furnace are tapped continuously through a single taphole into molds. The discard slags have a 1 to 2% lead oxide content and 1 to 2% of lead metal prills (pellets). 

Sodium nitrite has been synthesized by a number of chemical reactions involving the reduction of sodium nitrate [7631-99-4] NaNO. These include exposure to heat, light, and ionizing radiation (2), addition of lead metal to fused sodium nitrate at 400—450°C (2), reaction of the nitrate in the presence of sodium ferrate and nitric oxide at - 400° C (2), contacting molten sodium nitrate with hydrogen (7), and electrolytic reduction of sodium nitrate in a cell having a cation-exchange membrane, rhodium-plated titanium anode, and lead cathode (8). 

The second set of experiments was carried out in 1929 by Paneth. The decomposition of tetramethyllead was carried out in such a way that the decomposition products were carried by a flow of inert gas over a film of lead metal. The lead was observed to disappear with re-formation of tetramethyllead. The conclusion was reached that methyl radicals must exist long enough in the gas phase to be transported from the point of decomposition to the lead film, where they were reconverted to tetramethyllead. 

Imports of lead metal, which accounted for 17.5% of U.S. domestic consumption in 1996, rose from 90,900 metric tons in 1990 to 268,000 metric tons in 1996 and dropped slightly to an estimated... 

Exports of lead metal increased from 55,500 metric tons in 1990 to 94,400 metric tons in 1991, then fell to 44,000 metric tons in 1996 and 37,400 metric tons in 1997. In 1997, the U.S. exported lead metal primarily to South Korea, Canada, United Kingdom, Malaysia, Belgium, and Taiwan. Lead waste and scrap exports, which amounted to 71,900 metric tons in 1990, rose to 104,300 metric tons in 1995, dropped to 85,300 metric tons in 1996, and rose to 88,400 metric tons in 1997. The lead content of exported scrap lead-acid batteries went from 4,800 metric tons in 1990 to 1,400 metric tons in 1995. No later export tonnage figures for scrap lead-acid batteries are available for 1996 because the data were collected by dollar value only. Most exports are in the form of lead-acid batteries or products containing either lead-acid batteries or other applications of lead (Larrabee 1998 Smith 1998). 

As before, the subscript s denotes solid phases, and the subscript aq denotes solvated ions in solution. As a result of this process, a deposit of lead metal is formed on the electrode surface at the end of the cathodic scan while CO2 diffuses to the... 

Upon repetitive cycling of the potential scan, the voltammetric record is reproduced, but an additional cathodic peak near to -0.45 V appears. This is due to the reduction of Pb + ions electrochemically generated by the previous oxidation of lead metal. The reduction of lead ions occurs at a potential different from that at which the reduction of PbCOs takes place. In repetitive voltammetry, additional anodic peaks appear at -0.40 and -0.28 V. These are due to the oxidative dissolution of different lead deposits generated in reductive scans [130, 131]. 

In some cases, the deposit of lead metal also consist of irregular aggregates far from the original particles of the lead compound [126], as can be seen in Fig. 2.10 for minium (Pb304)—another widely used pigment These features can be rationalized, assuming that the electrochemical pathway represented by Eq. 2.6 can eventually be coupled by a reductive process via formation of Pb + in solution... 

Calculate the resultant temperature when 100 g of lead metal at 200.0°C are mixed with 200 g of water at 20.0°C. (Assume no heat loss to container or surroundings.)... 

Lead curse tablets from Roman Carthage contain variable amounts of very small metallic inclusions. Electron microprobe analysis confirmed these metallic inclusions were bronze, brass, and a Sn-Sb alloy. This was interpreted as possible evidence of lead metal recycling. Six samples were chosen to represent a range of tablets containing the minimum to the maximum number of inclusions. Thermal ionization mass spectrometry of the Pb isotopes in the curse tablets appear to define a mixing line, with the tablets containing the least number of inclusions plotting closest to the Tunisian lead ore isotope ratios. 

The non-oxidative dissolution of galena (PbS) in acidic solutions is an attractive first step in a hydrometallurgical process for the production of lead metal. The formation of relatively stable chloro complexes with lead ions (/ 3 = 2) results in a displacement of the equilibrium of the reaction... 

By Reaction of Lead Metal and Lead Alloys with Organic Esters. .. 250... 

Finely-divided lead metal is also reactive with alkyl halides and other alkyl esters to form R4Pb 161.240), The reaction of lead metal with ethyl iodide was reported by Cahours 62,63) to give an organolead product, at about the same time as Lowig published his papers. The reaction with ethyl chloride has been considered as a way of utilizing the by-product lead metal from the NaPb-C2H5Cl reaction, but it has not been commercialized because it requires an iodine catalyst and because two thirds of the lead metal is converted to lead(II) chloride, according to ... 

These reactions of lead metal and lead alloys with alkyl esters are conducted at elevated temperatures (usually above 80 °C) and at elevated pressure (autogenous pressure of RX), and in the presence of a suitable catalyst, such as ethers, amines, iodides, dependent on the particular system involved. Despite the large number of systems which have been investigated, none has been found to be as economical for the commercial production of tetramethyllead and tetraethyllead as the sodium-lead alloy reaction, with the possible exception of the electrolytic process developed by Nalco Chemical Company for tetramethyllead. Electrolytic processes are discussed in Section 6. 

Note that the stoichiometry is identical to that of the low temperature method, although the formation of an R3PbM compound is probably not involved. The higher temperature reaction can be run with the RX present throughout, or step (a) can be conducted in the absence of RX and the formation of lead metal permitted. In the second step (b), RX and more RM are added to the crude reaction mixture and the finely divided lead metal is converted to R4Pb. The methyl, ethyl and phenyl derivatives of R4Pb have been prepared in this fashion. 

The price of tetraalkyllead compounds is quite dependent on the price of lead metal, the most expensive raw material component. Thus, prices of commercial antiknock fluids fluctuate from time to time. The price of tetramethyllead fluid is generally several cents per pound higher than that of tetraethyllead fluid, reflecting the higher cost of manufacture. Because of the higher price of tetramethyllead, comparatively little of it is used alone 16,200). 

The solid residue from the acetate distillation is generally removed and calcined, then extracted with the combined phlegm and crystallized to obtain the Salt. The distillation residue from lead is interesting as it is mostly composed of fine particles of lead metal and will rapidly oxidize on exposure to the air. Very often it will ignite on its own and become like a red hot coal, burning itself to ashes. 

With dilute solutions (using 0 25m lead nitrate and 0- 125m sodium tetrahydroxo-stannate(II) reagent) the formation of the black precipitate of lead metal is not observable within an hour. In the presence of bismuth the reaction is accelerated at the same time bismuth is also precipitated ... 

In a variation of this procedure, the lead oxide can be mixed with lead sulfide and heated. The reaction that takes place results in the formation of lead metal and sulfiir dioxide gas. 

Lead is a reactive metal, but its reactivity is somewhat inhibited by the formation of an outer skin of protective compounds. For example, when a freshly cut piece of lead metal is exposed to the air, it quickly reacts with oxygen to form a thin outer layer of lead oxide. This outer layer then prevents further reaction between the metal and oxygen and other constituents of the air. A similar phenomenon occurs when lead metal is placed into water. Compounds present in water react with lead to form an outer skin of lead carbonate, lead silicate, or similar compounds that protect the metal from further attack. This property helps to explain the long popularity of lead for the lining of pipes designed to carry many different kinds of liquids. 

A lead storage battery is not a dry cell because it contains several connected cells filled with an aqueous solution of sulfuric acid, which serves as the electrolyte. The electrodes are alternating plates of lead metal and lead(lV) oxide. The case surrounding the battery is hard plastic. It holds the cells in place and acts as an insulator because it does not conduct electricity itself. This helps keep the electricity inside the battery. 

In this cell the anode is constructed of lead metal, which is oxidized. In the cell reaction, lead atoms lose two electrons each to form Pb ions, which combine with ions present in the solution to give solid PbSO. ... 

Note that there are several modern versions of the Barbier reaction that use transition metals or their derivatives.Examples include indium metal, samarium iodide, and lead. An example using lead reacted benzaldehyde with allyl bromide in the presence of lead metal to give a 99% yield of 45.56 A retro-Barbier fragmentation has also been reported in which an alcohol was treated with 10 equivalents of bromine and 15 equivalents of potassium carbonate in chloroform to give a bromo ketone.5 ... 

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