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The most important Permian economic deposits are rock salt and potash salts,
coal, oil, and gas. Economically important evaporites (salts formed by chemical
precipitation under generally arid conditions) of Permian age are found in the ...
The most important terpene, as the isoprene polymers are called, is rubber that
exists in the sap of many tropical trees, especially of the genus Hevea. Rubber is
a polyhy- drocarbon and consists, in the native state, of long chains of isoprene, ...
There are two varieties of polypropylene: a soft, rubbery type of minor importance
and a hard, crystalline, high-melting type, which is a valuable thermoplastic
material of wide applications in certain areas of the textile industry and also used
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The New Encyclopaedia Britannica (Encyclopaedia)User Review - Not Available - Book Verdict
For virtually all its 238 years,Britannica has ruled the shelves as a peerless general encyclopedia. Reviewers have consistently given it high marks for most of the 12 criteria identified inKister's ... Read full review