Effect basic lead carbonate

It has been found that red lead, litharge and certain grades of metallic lead powder render water alkaline and inhibitive this observation has been confirmed by Pryor . The effect is probably due to a lead compound, e.g. lead hydroxide, in solution. Since, however, atmospheric carbon dioxide converts these lead compounds into insoluble basic lead carbonate, thereby removing the inhibitive materials from solution, these pigments may have only limited inhibitive properties in the absence of soap formation. 

In these experiments, carried out statically under one atmosphere of carbon dioxide, only basic lead carbonate was detected. Basic lead azide and normal lead carbonate were not obscncd by X-ray diffraction [48]. This is probably due to a "cocoon effect," with basic lead azide surrounding the kernel center, basic lead carbonate as an intermediate layer, and a thin outer skin of the normal carbonate. It seems likely that in preparation of the sample for X-ray diffraction analysis the basic lead carbonate masked the normal lead carbonate below the X-ray diffraction detection threshold, as noted by Todd [49]. 

Lead Compounds—These were among the earliest stabilizers. Although quite effective as heat stabilizers, they are toxic, impart opacity to PVC compounds, and cause black coloration with time because of poor sulfide stain resistance. The primary use for lead compounds is in electric applications such as wire coatings. The principal lead compounds for this use are tribasic lead sulfate, basic lead sulfate silicate, basic lead carbonate, and basic lead phthalate. Use levels usually range from 3 to 8 parts-per-hundred parts of PVC (phr). 

Stabilizers are almost invariably added to PVC to improve its heat and light stability. The species found effective in stabilizing PVC are those that are able to absorb or neutralize HCl, react with free radicals, react with double bonds, or neutralize other species that might accelerate degradation. Lead compounds, such as basic lead carbonate and tribasic lead sulfate, and metal soaps of barium, cadmium, lead, zinc, and calcium are used as stabilizers. Obviously, they can react with HCl. Epoxy plasticizers aid in stabilizing the resin. Another group of stabilizers are the organotin compounds, which find application because of their resistance to sulfur and because they can yield crystal-clear compounds. 

Basic lead carbonate n. 2PbC03 Pb(0H)2. A very effective heat stabilizer, used where toxicity is of no concern as in electrical-insulating compounds. Its use is limited because of its tendency to form blisters during processing and to cause spew when exposed to weather, also by rising concern about lead in the environment. Gooch JW (1993) Lead based paint handbook. Plenum Press, New York. 

Lead stabilizer Any of a large family of highly effective heat stabilizers that are limited to use in apphcations where toxicity, sulfur staining, and lack of clarity are not objectionable. Examples are basic lead carbonate, basic lead sulfate complexes, basic silicate, or white lead, co-precipitated lead silicate, and silica gel, dibasic lead maleate. 

Some stabilizers are effective in improving weathering behaviour. Lead compounds are good heat stabilizers basic lead carbonate or tribasic lead sulphate are favoured stabilizers but are toxic. The stearate, palmitate and octoate salts of Cd, Ba, Ca, Zn are increasingly used, but toxicity limits the range of applications for Cd. Organo-tin compounds are also effective stabilizers, especially for transparent products, but may also be somewhat toxic. 

Various other soft materials without the layer—lattice stmcture are used as soHd lubricants (58), eg, basic white lead or lead carbonate [598-63-0] used in thread compounds, lime [1305-78-8] as a carrier in wire drawing, talc [14807-96-6] and bentonite [1302-78-9] as fillers for grease for cable pulling, and zinc oxide [1314-13-2] in high load capacity greases. Graphite fluoride is effective as a thin-film lubricant up to 400°C and is especially useful with a suitable binder such as polyimide varnish (59). Boric acid has been shown to have promise as a self-replenishing soHd composite (60). 

The metal is very effective as a sound absorber, is used as a radiation shield around X-ray equipment and nuclear reactors, and is used to absorb vibration. White lead, the basic carbonate, sublimed white lead, chrome yellow, and other lead compounds are used extensively in paints, although in recent years the use of lead in paints has been drastically curtailed to eliminate or reduce health hazards. 

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