Lead :: essays research papers

Lead is a lustrous, silverymetal that tarnishes in the presence of air and becomes a dull bluishgray. Soft and flexible, it has a low melting point (327 C). Its chemicalsymbol, Pb, is from plumbum, the Latin word for waterworks, because of reachs large use in past water pipes. Its atomic number is 82 itsatomic weight is 207.19.Lead and use up compounds can be highly hepatotoxicwhen eaten or inhaled. Although lead is absorbed very slowly into thebody, its rate of excreting is even slower. Thus, with constant exposure,lead accumulates gradually in the body. It is absorbed by the red bloodcells and circulated through the body where it becomes concentrated inthe softish tissues, especially the liver and kidneys. Lead can cause disparagein the central nervous system and app arntly can damage the cells fashioningup the blood-brain barrier that protects the brain from many harmful chemicals.Symptomsof lead toxic condition include loss of appetite, weakness, anemia, vomiting,and co nvulsions, sometimes leading to permanent brain damage or death.Children who ingest chips of old, lead-containing paint or are exposedto dispel from the deterioration of such paint may exhibit symptoms. Levelsof environmental lead considered nontoxic may also be involved in increasehypertension in a significant number of persons, according to studiesreleased in the mid-1980s. As a result, the U.S. Centers for Disease Controlin recent eld have been revising downward the levels of environmentallead that it would consider safe. At one time, lead poisoning was commonamong those who worked with lead, but such workplace hazards have beenlargely curtailed.Lead has been used by humans since ancient times.It was used in ancient Egypt in coins, weights,ornaments, utensils,ceramic glazes, and join. Lead is mentioned in the Old Testament. TheRomansconveyed drinking water in lead pipes, some of which are still in operation.Roman slavesextracted and prepared the lead, describes a disease amon gthe slaves that was all the way lead poisoning. Because of their potentialtoxicity, lead water pipes are no all-night being installed. The greatestsingle use of lead metal straightaway is in the plates of storage batteries forautomobiles.The protective oxidation layer formed by lead in contactwith such substances as air, sulfuric acid,and farad makes it highlyresistant to corrosion. For this reason, lead has been used to makedrainagepipes and lead chambers in sulfuric acid factories. It is also used asa roofing material. Thesoftness and malleability of lead make it expedientfor sheathing telephone and television cables. Lead isused in solderbecause of its low melting point. When combined with tin, lead forms solder