Pyrophoric lead

Acyl halides can be coupled with pyrophoric lead to give symmetrical a-diketones in... 

The disadvantages of the PMS precursor are (1) MeSiFl3 is costly and pyrophoric, forming potentially explosive mixtures with ambient air, (2) the Ti/Zr dehydropolymerization catalysts are also pyrophoric, leading to pyrophoric PMS and (3) metallocene-derived PMS is also highly pyrophoric. For example, a 20 wt% increase was observed after exposure of PMS samples to dry air for 5 h at RT. In contrast, the mPMS derivative mentioned above exhibits only a 3 wt% increase in air over a 5 h period. 

Chlorpromazine undergoes a Wurtz condensation on passing through a column filled with pyrophoric lead, giving bispromazine (129) in 90% yield. ... 

The Hungarian chemist Mezaros1 states that pyrophoric lead can be prepared by reaction of lead oxide with furfural vapors at 290°. It can be purified by washing with benzene and aqueous alcohol. It is described as a new reagent for Wurtz-like reactions, for example ... 

Finely divided lead, when heated in air, forms first the lead(II) oxide, litharge , PbO, and then on further heating in an ample supply of air, dilead(II) lead(IV) oxide, red lead , Pb304. Lead, in a very finely divided state, when allowed to fall through air, ignites and a shower of sparks is produced. Sueh finely divided powder is said to be pyrophoric . It can be prepared by carefully heating lead tartrate. 

Reactivity (instability) information Acceleration rate calorimetry Differential thermal analysis (DTA) Impact test Thermal stability Lead block test Explosion propagation with detonation Drop weight test Thermal decomposition test Influence test Self-acceleration temperature Card gap test (under confinement) JANAE Critical diameter Pyrophoricity... 

Inorganic oxides are usually prepd by intimate contact between the element and oxygen or air. The reaction may be rapid and exothermic, as when finely divided pyrophoric materials ignite spontaneously in air or oxygen. Examples of these materials are iron, lead and phosphorus.-Or, the reaction may be slow as when iron oxidizes when exposed to ordinary moist air, or when aluminum oxidizes at the surface upon exposure to air. Much of the time oxidation re-... 

Tin finds widespread use because of its resistance to corrosion, or as foil or to provide protective coats/plates for other metals. Properties of lead which make industrial application attractive surround its soft, plastic nature permitting it to be rolled into sheets or extruded through dies. In the finely-divided state lead powder is pyrophoric in bulk form the rapidly-formed protective oxide layer inhibits further reaction. It dissolves slowly in mineral acids. Industrial uses include roofing material, piping, and vessel linings, e.g. for acid storage. 

Safety. The MR is much safer than the MASR. (1) The reaction zone contains a much smaller amount of the reaction mixture (hazardous material), which always enhances process safety. (2) In case of pump failure, the reaction automatically stops since the liquid falls down from the reaction zone. (3) There is no need to filter the monolithic catalyst after the reaction has been completed. Filtration of the fine catalysts particles used in slurry reactors is a troublesome and time-consuming operation. Moreover, metallic catalysts used in fine chemicals manufacture are pyrophoric, which makes this operation risky. In a slurry reactor there is a risk of thermal runaways. (4) If the cooling capacity is insufficient (e.g. by a mechanical failure) a temperature increase can lead to an increase in reaction, and thus heat generation rate. 

The finely divided (pyrophoric) oxide incandesces with nitric acid. Lead-containing rubber... 

The finely divided lead produced by reduction of the oxide with furfural vapour at 290°C is pyrophoric and chemically reactive. 

Alloys of reactive metals are often more pyrophoric than the parent metals. Examples are alloys of titanium with zirconium thorium with copper, silver or gold uranium with tin, lead or gold magnesium with aluminium hafnium with iron [1], Cerium amalgams and thorium-silver alloys are spontaneously flammable when dry [2], Individually indexed alloys are ... 

In very finely divided form, lead is pyrophoric. When heated in oxygen or air, the metal forms lead monoxide, PbO, which is oxidized further in the presence of excess oxygen or air to lead tetroxide, Pb304. The finely divided metal dissolves in a solution of sodium in hquid ammonia, forming a green solution of Na4Pbg. 

A common problem of this synthesis is the decomposition of the product to a black insoluble and pyrophoric powder (presumably metallic Mo), which is possibly caused by the use of an impure starting material, to the adventitious introduction of air, to excessive exposure to light, or to a combination of those factors. If a black powder is formed, this can be removed at the end of the reaction by filtration through a glass frit the subsequent workup is as described above. Such decomposition reduces the yield but does not lead to a less pure product. If larger amounts of Mo(CO)6 are used, the sublimation of larger quantities of Mo(CO)6 to the condenser occurs, which may require interruption of the procedure and manual scraping of the sublimed solid back into the flask with a spatula under a flow of N2. 

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