The New Encyclopędia BritannicaEncyclopędia Britannica, 1983 - Encyclopedias and dictionaries |
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Page 140
... chemical control , and biological means fell into neglect . The extensive use of powerful chemical agents soon resulted in a number of serious ecological problems . Consequently , current pest control practice minimizes the use of ...
... chemical control , and biological means fell into neglect . The extensive use of powerful chemical agents soon resulted in a number of serious ecological problems . Consequently , current pest control practice minimizes the use of ...
Page 187
... chemicals from this source dates from 1919. Catalytic cracking is a valuable source of propylene and n - butylenes but not a very good one of ethylene , a most important petroleum chemical . It is important to differentiate between the ...
... chemicals from this source dates from 1919. Catalytic cracking is a valuable source of propylene and n - butylenes but not a very good one of ethylene , a most important petroleum chemical . It is important to differentiate between the ...
Page 388
... chemical knowledge . Chemists tended to build detailed systems , " chemical philosophies , " attempting to explain the entire universe in chemical terms . Most chemists ac- cepted the traditional four elements ( air , earth , water ...
... chemical knowledge . Chemists tended to build detailed systems , " chemical philosophies , " attempting to explain the entire universe in chemical terms . Most chemists ac- cepted the traditional four elements ( air , earth , water ...
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activity America animals appear areas atoms became become body called camera century changes characteristics chemical Church colour common complete compounds consists containing continued drugs early effect electrons elements energy example existence experience Family field Figure fins fishes groups human important increase individual industry Italy known later lens less light liquid living lower major material means ment methods move movement natural North object occur organic original Peking Pentecostal percent period permafrost personality pest Peter petroleum Philip philosophy photographs plants political position possible practice present printing problems production Quakers range region result rocks similar social South species structure surface temperature theory tion United usually widely