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Date: 14-12-2018
1035
Date: 28-10-2018
975
Date: 16-1-2018
744
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Extraction and manufacture of the group 14elements
Sources of natural graphite are supplemented by manufactured material formed by heating powdered coke (hightemperature carbonized coal) with silica at ≈ 2800 K. Approximately 30% of diamonds for industrial use in the US are synthetic. Diamond films may be grown using a chemical vapour deposition method and hydrothermal processes are currently being investigated. The manufacture of amorphous carbon (carbon black, used in synthetic rubbers) involves burning oil in a limited supply of air. Silicon (not of high purity) is extracted from silica, SiO2,
by heating with C or CaC2 in an electric furnace. Impure Ge can be obtained from flue dusts collected during the extraction of zinc from its ores, or by reducing GeO2 with H2 or C. For use in the electronic and semiconductor industries, ultrapure Si and Ge are required, and both can be obtained by zone-melting techniques . Tin is obtained from cassiterite (SnO2 ) by reduction with C in a furnace but a similar process cannot be applied to extract Pb from its sulfide ore since ΔfGo (CS2,g) is 67 kJ mol-1; thermodynamically viable processes involve the below reactions at high temperatures. Both Sn and Pb are refined electrolytically.
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علامات بسيطة في جسدك قد تنذر بمرض "قاتل"
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أول صور ثلاثية الأبعاد للغدة الزعترية البشرية
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مكتبة أمّ البنين النسويّة تصدر العدد 212 من مجلّة رياض الزهراء (عليها السلام)
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