| 单词 | fractional distillation |
| 释义 | > as lemmasfractional distillation As shown by the etymology, the original application is to substances of which the distillates are condensed drop by drop into the liquid form; whether for the purpose of extracting the more volatile part of a substance, or of concentrating or purifying a volatile substance such as water by freeing it from matter held in suspension or solution. When no more heat is applied than just suffices to cause the liquid to pass over in drops, the process is called cold distillation. Dry or destructive distillation, the decomposition of a substance by strong heat in a retort, and the collection of the volatile matters evolved, as in the destructive distillation of coal in gas-making. fractional distillation, the separation of two or more volatile liquids having different boiling-points, so that they pass over at different temperatures and can be collected separately, the more volatile first, and the less volatile in order afterwards. distillation by descent (per descensum), in Old Chemistry, the name given to a method in which the fire was applied above, and the distillate drawn off beneath (see descent n. 11). In opposition to this, the ordinary method was called distillation by ascent (per ascensum).extracted from distillationn.fractional distillation 2. Chemistry. Designating a process in which different fractions of a mixture are separated in consequence of their differing physical properties. So fractional crystallization, fractional distillation (see distillation n. 3), fractional precipitation, etc. ΘΚΠ the world > matter > chemistry > chemical reactions or processes > [adjective] > of or relating to named chemical reactions or processes > of or relating to fractionation fractional1857 1857 W. A. Miller Elements Chem. III. i. 9 This process of fractional distillation is well adapted to the separation of liquids. 1886 Chem. News 10 Sept. 131/1 Fractional crystallisation has yielded new results with didymium. 1886 Chem. News 10 Sept. 131/1 Working with the samarskite earths, fractional precipitation with oxalic acid separates first erbia, holmia, and thulia, then terbia, and lastly yttria. 1897 G. F. Becker in Amer. Jrnl. Sci. 154 257 (heading) Fractional crystallization of rocks. 1897 G. F. Becker in Amer. Jrnl. Sci. 154 258 The process..usually known as fractional crystallization..has been employed in the purification of compounds ever since chemistry was pursued. 1949 A. E. Alexander & P. Johnson Colloid Sci. II. xxvii. 797 Fractional solution may also be employed, a series of solvents of increasing solvent power being used to extract the unfractionated polymer. 1950 N. V. Sidgwick Chem. Elements I. 456 Fractional precipitation of the hydroxides is useful in isolating the very weakly basic Sc(OH)3 or the strongly basic La(OH)3. 1960 F. J. Turner & J. Verhoogen Igneous & Metamorphic Petrol. (ed. 2) iv. 85 The nature of the liquid fraction of a crystallizing magma at a given moment depends on..the degree to which fractional crystallization has already been effective. 1966 McGraw-Hill Encycl. Sci. & Technol. (rev. ed.) XI. 118 Fractional distillation to remove iron, lead, and cadmium from crude zinc. 1968 J. M. Coulson & J. F. Richardson Chem. Engin. (ed. 2) II. xiv. 577 It is often possible to separate a mixture of two soluble salts by fractional crystallization. < as lemmas |
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