Lead compounds Pb

The lead compounds PbS, PbSe, PbTe are narrow-gap semiconductors that have been widely investigated for infrared detectors, diode lasers, and thermo-photovoltaic energy converters. Their photoconductive effect has been utilized in photoelectric cells, e.g., PbS in photographic exposure meters. Integrated photonic devices have been fabricated by their heteroepitaxial growth on Si or III-V semiconductors. 

Fig. 1. LC—ICP-MS chromatogram of a standard mixture of organolead and inorganic lead compounds (Pb, trimethyllead and triethyllead) using reversed-phase HPLC. Mobile phase, 0.1 M ammonium acetate and 0.1 M acetic acid at pH 4.6, 30%...

Pb NMR of Crystalline Lead Compounds Pb NMR of Lead-Containing Glasses ° Pb in Sol-Gel Prepared Ceramics... 

Oxidation of the lead sulphide feed occurs with coincidental volatilization of the lead compounds PbS and PbO. Therefore, a maximum rate of PbS volatilization from the flame is noted during the intermediate step of feed oxidation. This follows from the relations of the lead sulphide volatilization rate ... 

Lead fluorides are highly toxic and should be handled with great care. The ACGIH adopted toxicity value for lead compounds as Pb is TWA 0.15 mg/m and for fluorides as F 2.5 mg/m. PbF is prepared by the action of elemental fluorine on very dry Pbp2 at 280—300°C (15). 

URANIUM compounds), Pb from the thorium series, and Pb from the actinium series (see Actinides and transactinides). The crystal stmcture of lead is face-centered cubic the length of the edge of the cell is 0.49389 nm the number of atoms per unit cell is four. Other properties are Hsted in Table 1. 

In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

Tetravalent lead is obtained when the metal is subjected to strong oxidizing action, such as in the electrolytic oxidation of lead anodes to lead dioxide, Pb02 when bivalent lead compounds are subjected to powerful oxidizing conditions, as in the calcination of lead monoxide to lead tetroxide, Pb O or by wet oxidation of bivalent lead ions to lead dioxide by chlorine water. The inorganic compounds of tetravalent lead are relatively unstable eg, in the presence of water they hydrolyze to give lead dioxide. 

Most oxoacid derivatives of lead are Pb" compounds, though Pb(OAc)4 is well known and is extensively used as a selective oxidizing agent in organic chemistry.It can be obtained as... 

Many of the metals used by ancient man— coppei (cuprum, Cu), silver (argentum, Ag), gold (aurum, Au), tin (stannum, Sn), and lead (plumbum, Pb)—are in relatively short supply. Ancient man found deposits of the first three occurring as the elementary metals. These three may also be separated from their ores by relatively simple chemical processes. On the othei hand, aluminum and titanium, though abundant, are much more difficult to prepare from their ores. Fluorine is more abundant in the earth than chlorine but chlorine and its compounds are much more common—they are easier to prepare and easier to handle. However, as the best sources of the elements now common to us become depleted, we will have to turn to the elements that are now little used. 

Lead forms two types of chemical compounds lead (II), and lead (IV) compounds based on Pb24 and Pb4 ions, where those based on Pb2 ions are the more stable. The metal is oxidized even at room temperature to lead oxide (PbO) and also by water that contains oxygen and forms lead hydroxide (Pb(OH),). In the lead-acid battery, the (less stable) lead (IV) oxide (lead dioxide, Pb02), is of greatest importance. Beside these two, a number of oxides are observed in the battery that are mostly mixtures. A brief survey will now be given of those compounds that are of interest for lead-acid batteries. 

In analogous reactions arylmetal compounds of thallium (ArTICl, addition of Tl-Na alloy, Nesmeyanov and Makarova, 1952), of tin (Ar2SnCl2, addition of Sn, Nesmeyanov et al., 1936), of lead (Ar4Pb, Pb-Na alloy, Nesmeyanov and Makarova, 1954 Nesmeyanov et al., 1954) were obtained (yields up to 80% with Hg, 10-40% with the other metals). Tetravalent metal salts often react to give a mixture of partially arylated metal chlorides (ArwMCl4 , n = 1 to 3). Waters (1939) was one of the few chemists outside Nesmeyanov s school who worked on that subject (arylation of lead). 

Studies of the thermal decarboxylation of phenylpropiolates of copper, tin, and lead parallel those of the corresponding cyanoacetate compounds. Copper phenylpropiolate decarboxylated irreversibly in dmf at 35°C and reversibly in the presence of tertiary phosphines in dmf (52). Triorga-iio(phenylethynyl)tin and -lead compounds, R3MC=CPh [M=Sn, R = Ph or Bu (53) M = Pb, R = Ph (5/)], were isolated when the triorganotin or -lead phenylpropiolates, R3M02CC=CPh, were heated in vacuo. Triphenyllead phenylpropiolate also decarboxylated in refluxing toluene (54). 

A blank and also a sterile solution containing Pb2+ of methyllead compounds showed no Pb content in the methanolic solution after the same treatment. The author concluded that Me4Pb was produced in the biomethylation of Pb2+ by bacteria123. Thompson and Crerar122 also observed that about 0.03% of lead as Pb(NC>3)2 underwent methylation and trimethyllead acetate, (CH3)3PbOAc, was methylated nearly quantitatively in incubation experiments with marine sediments from the British Columbia coastline. 

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