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Lead (/ l ɛ d /) is a chemical element; it has symbol Pb (from Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to ...
Tarnished lead (left) and shiny lead (right) Compounds of lead exist with lead in two main oxidation states: +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions. [1] Red α-PbO and yellow β-PbO The mixed valence oxide Pb 3 O 4 Black PbO 2 which is a strong ...
Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish, although it may tarnish with oxygen over time. It often appears as a dull, gray or black film or coating over metal. Tarnish is a surface phenomenon that is self-limiting, unlike rust. Only the top few layers of the ...
Work the paste into the crevices, turning the cloth as it gets gray. Rinse and buff dry. For silver jewelry that is tarnished, apply a tiny dab of white paste toothpaste (not gel) on a soft cloth ...
Tin-lead solders (Sn50Pb50, Sn60Pb40, Sn63Pb37) can be conditionally used when the apparatus is not to be baked and operating temperatures aren't elevated (lead tends to outgas). A better choice for vacuum systems is the tin-silver eutectic, Sn95Ag5 (Sn-Ag eutectic is actually 96.5-3.5); its melting point of 230 °C (446 °F) allows bakeout up ...
The focus on lead exposure for babies and young children is greater because they absorb four to five times as much ingested lead as adults from any given source, according to WHO.
Older pewters with higher lead content are heavier, tarnish faster, and their oxidation has a darker, silver-gray color. [10] Pewters containing lead are no longer used in items that will come in contact with the human body (such as cups, plates, or jewelry), due to the toxicity of lead. Modern pewters are available that are completely free of ...
Hypoallergenic, nickel- and lead-free, these hoops are plated in 14k gold and are eye-catching without being overdone. ... in the shower, to the beach and at work; they have not tarnished at all ...