Lead halides, 221

In gasoline engines lead halides accumulate in the lubricant occasionally these give rise to the corrosion of aluminium-alloy pistons and very rarely to corrosion on aluminium-tin bearings. ... 

Patterson thought he could identify the culprit If the high concentrations of lead observed in a few surface waters of the Pacific were representative of the sea surface of the entire northern hemisphere, the bulk of this lead could be readily be accounted for as originating from leaded gasolines. The hypothesis was unproven, but Patterson immediately understood its social implications. Automobile exhaust emitted lead as soluble lead-halide particles, which humans and other mammals easily absorb. When Patterson reported his ocean sediment research in an encyclopedic, 45-page article in 1962, he handed a copy to a colleague saying, Read it. It s important. ... 

Thomas G. Spiro and William M. Stigliani. Chemistry of the Environment. New Jersey Prentice Hall, 1996. Source for lead-halide particles lead paint on school buses, highways, and bridges. 

Information available regarding the chemistry of lead in air is limited. Before the ban on sales of leaded gasoline, lead particles were emitted to the atmosphere from automobiles as lead halides (mostly PbBrCl) and as double salts with ammonium halides (e.g., 2PbBrCl NH4Cl. Pb3[P04]2, and PbS04 [Biggins and Harrison 1979 Ter Haar and Bayard 1971]). After 18 hours, approximately 75% of the bromine and 30-40% of the chlorine disappeared, and lead carbonates, oxycarbonates and oxides were produced. 

In densely packed solids without obvious open channels, the transport number depends upon the defects present, a feature well illustrated by the mostly ionic halides. Lithium halides are characterized by small mobile Li+ ions that usually migrate via vacancies due to Schottky defects and have tc for Li+ close to 1. Similarly, silver halides with Frenkel defects on the cation sublattice have lc for Ag+ close to 1. Barium and lead halides, with very large cations and that contain... 

K. Chondroudis and D.B. Mitzi, Electroluminescence from an organic-inorganic pereovskite incorporating a quaterthiophene dye within lead halide perovskite layer, Chem. Mater., 11 3028-3030,1999. 

Lead fluoroborate hydrate, 4 157t, 158, 159 Lead-free (LF) solder, 20 60-61 24 796 Lead halides, 14 784-786... 

Dibromoethane has been and is still used in a variety of ways. The main use is as an additive in leaded gasoline where 1, 2-dibromoethane acts as a "scavenger" that converts lead oxides in cars to lead halides these are released more easily with engine exhaust (Fishbein 1980 Stenger 1978). 

Several additive compounds of ammonia and lead halides have been described. 

Ammino-derivatives op Subgroup B—Derivatives of Tin Halides, Lead Halides. Chapter VIII. Metal - Ammines of Elements of Group V. 

It remains to be determined to what extent the dye adsorption technique is applicable to other substrates. No evidence was obtained for Pseudocyanine adsorption to Mn02, Fe2Os or to pure silver surfaces, although this dye can be bound to mica, lead halides, and mercury salts with formation of a /-band (61). Not only cyanines but other dye classes can yield surface spectra which may be similarly analyzed. This is specifically the case with the phthalein and azine dyes which were recommended by Fajans and by Kolthoff as adsorption indicators in potentio-metric titrations (15, 30). The techniques described are also convenient for determining rates and heats of adsorption and surface concentrations of dyes they have already found application in studies of luminescence (18) and electrophoresis (68) of silver halides as a function of dye coverage. 

Reactions of photoelectrons with cation defects as described here have also been found for mercury halides or for oxalates of Fe and Pd. Lead halides, in contrast, possess mobile anions which can trap photoelectron holes. In this case, the absorption of photons leads immediately to a positive image, where the illuminated areas appear light. 

Various lead halide sulfides are reported in the literature. They precipitate when acidic solutions of lead halides react with hydrogen sulfide. Most probably the lead(II) chaicogenide halides described below are the only stable ones among these compounds. The conditions for the syntheses of these materials are given in Table V. 

The mechanism of poisoning automobile exhaust catalysts has been identified (71). Upon combustion in the cylinder tetraethyllead (TEL) produces lead oxide which would accumulate in the combustion chamber except that ethylene dibromide [106-93 4] or other similar halide compounds were added to the gasoline along with TEL to form volatile lead halide compounds. Thus lead deposits in the cylinder and on the spark plugs are minimized. Volatile lead halides (bromides or chlorides) would then exit the combustion chamber, and such volatile compounds would diffuse to catalyst surfaces by the same mechanisms as do carbon monoxide compounds. When adsorbed on the precious metal catalyst site, lead halide renders the catalytic site inactive. 

The ammonia syntheses of heteronuclear complexes with use of elemental copper, lead halides, and aminoalcohols (3.273) [679-681] are significant, since... 

Salt-elimination reactions between transition metallates and lead halides... 

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