أكتوبر 20th, 2018

 

Astatin

Astatine A chemical element, At, atomic number 85. Astatine is the heaviest of the halogen groups, filling the place immediately below iodine in group 17 of the periodic table. Astatine is a highly unstable element existing only in short-lived radioactive forms. About 25 isotopes have been prepared by nuclear reactions of artificial transmutation. The longest-lived of these is 210At, which decays with a half-life of only 8.3 h….

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Aspartame

Aspartame A white, crystalline compound, 1-aspartyl-1-phenylalanine methyl ester (APM), with formula as shown in the figure. It is slightly soluble in water. Its sweetening pro­perties were discovered accidentally in 1965 when the compound, a dipeptide, was produced as an intermediate in the synthesis of the C-terminal tetrapeptide of gastrin. Aspartame is the L,L-diastereoisomer; the three other possible diastereoiso­mers are not…

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Art conservation chemistry

Art conservation chemistry The application of chemistry to the technical examination, authentication, and preservation of cultural property. Chemists working in museums engage in a broad range of investigations, most frequently studying the chemical composition and structure of artifacts, their corrosion products, and the ma­terials used in their repair, restoration, and conservation. The effects of the museum environment, including air pollutants, fluctuations in temperature and relative humid­ity, biological activity,…

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