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liuxuanyan金虫 (小有名气)
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[求助]
怎么除去环己烷中的芳烃
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做紫外时需要环己烷作溶剂，我们实验室只有分析纯的，通过紫外扫描发现在250nm左右有吸收，请问在怎么除去环己烷中的芳烃，消除此段吸收？ 我用硫酸洗过后，吸收有减弱，但是再经过蒸馏，无水硫酸钠干燥后，在300-260nm间出现了强吸收，请问这是为什么？？ |
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月落之后，不说爱你*abcdelm
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2楼2007-06-07 20:18:32
liuxuanyan
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3楼2007-06-08 22:47:29
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liuxuanyan(金币+1):谢谢你，我去试试！
liuxuanyan(金币+1):谢谢你，我去试试！
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Cyclohexane [110-82-71 M 84.2, f 6.6O, b 80.7O, d24 0.77410, n 1.42623, n25 1.42354. Commonly, washed with conc H2SO4 until the washings are colourless, followed by water, aq Na2C03 or 5% NaOH, and again water until neutral. It is next dried with P2O5, Linde type 4A molecular sieves, CaC12, or MgS04 then Na and distd. Cyclohexane has been refluxed with, and distd from Na, CaH2, LiAl& (which also removes peroxides), sodiudpotassium alloy, or P2O5. Traces of *benzene can be removed by passage through a column of silica gel that has been freshly heated: this gives material suitable for ultraviolet and infrared spectroscopy. If there is much *benzene in the cyclohexane, most of it can be removed by a preliminary treatment with nitrating acid (a cold mixture of 3OmL conc HNO3 and 70mL of conc H2SO4) which converts *benzene into nitrobenzene. The impure cyclohexane and the nitrating acid are placed in an ice bath and stirred vigorously for 15min, after which the mixture is allowed to warm to 25O during lh. The cyclohexane is decanted, washed several times with 25% NaOH, then water dried with CaC12, and distd from sodium. Carbonyl-containing impurities can be removed as described for chloroform. Other purification procedures include passage through columns of activated alumina and repeated crystn by partial freezing. Small quantities may be purified by chromatography on a Dowex 710-Chromosorb W gas-liquid chromatographic column. Rapid purification: Distil, discarding the forerun. Stand distillate over Grade I alumina (5% w/v) or 4A molecular sieves. [ Last edited by jianmei97 on 2007-6-13 at 12:24 ] |
4楼2007-06-13 12:23:34
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