Zone melting and column crystallization as analytical tools.
Schildknecht, Hermann.
Anal. Chim. Acta (1967), 38(1-2), 261-73.
Journal in English. CAN 67:39936
Abstract
A micro-zone melting app., and a developed continuous flow column crystallizer are described. The methods of freezing out the solvent (Zonenschmelzen. Verlag Chemie: Weinheim. 1964. 226 pp.; Pfann: Zone Melting, 2nd Ed. Wiley: New York. 1966. 310 pp.), multistage crystn., micro zone melting, and column crystn. are used to sep. isomers, and for sepg. and identifying compds. in plant and animal products, and in meteorites. Pure C6H6 is prepd. by means of column crystn. The column crystn. app. consists of 2 concentric tubes with a metal spiral rotating in the annular space between them. Crystals are formed by cooling the top of the column, and are scraped off and carried down the column by the spiral action. Re-melting of the crystals at the bottom of the column forms liquid phase for contacting with the descending crystals. The H2O ext. of the ovules of Oenothera (CA 58: 12856g) was concd. by freezing most of the H2O; the concd. soln. contained detectable amts. of 14 compds. reacting with ninhydrin: 5 peptides, 1 amine, and 7 amino acids were identified. By chromatographing the concd. H2O ext., sucrose and 4 reducing sugars were found. By using a multi-stage zone-melting app. with several heaters and coolers, the purification of the 2,4-dinitrophenylhydrazone of Me2CO; PhNHAc, and the sepns. of a mixt. of 3,4- and 3,5-xylenol, and of tiglic, and angelic acid are described. Palmitic acid (identified by m.p. and ir spectrum) was isolated from adipocere by means of micro-zone melting. The EtOH soln. of 1 water beetle (bladder) was chromatographed on silica gel, giving 3 mg. of colorless crystals (m.p. 110°) which sublimed, but had a complex ir spectrum. After the passage of 20 zones through a micro-ingot, 2 fractions were first obtained; further zone melting gave a low melting fraction, and a eutectic, which was sepd. by thin-layer chromatog. The 3 fractions were identified, by means of ir and uv spectra and the m.p. of the 2,4-dinitrophenylhydrazone derivs., as BzOH, p-HOC6H4CHO, and p-HOC6H4CO2Me.
C6H6, used to ext. meteorite samples, is purified continuously in the column crystallizer; 30 ml./hr. of ultrapure C6H6 (I) was prepd. from the purest C6H6 available (II). The gas chromatogram of I has 1 peak of C6H6; that of II has elution peak of C6H6, and minor peaks due to methyl cyclopentane, thiophene, and aliphatic compds. An Aerograph chromatograph, with 5% Apiezon L column, and programed temp. of 40-160° (4°/min.) was used. The C6H6 ext. (6-8 days extn.) of Essebi meteorite was concd. by freezing most of the C6H6. The thin-layer chromatogram on silica gel G, of the concd. meteorite ext. in cyclohexane gave sep. spots of alkanes, S, aromatic, and acidic compds. 12 references.
Continuous multistage fractional crystallization. I. Laboratory investigation.
Betts, W. D.; Freeman, J. W.; McNeil, D.
J. Appl. Chem. (London) (1968), 18(6), 180-7.
Abstract
Lab. scale Schildknecht rotating helix crystallizers were constructed and used for sepns. of org. (79) and aq. (4) mixts. Columns operated continuously effected sepns. equiv. to 4-5 equil. sepns. at throughputs up to 1.5 l./hr. For complete sepn. in binary mixts. which form mixed crystals, it was necessary to rerun the conc. from the 1st pass. Sepns. effected on the aq. solns. of inorg. salts and EtOH indicate that these columns could be used for the desalination of water, concn. of aq. effluents, and concn. of beers and wines. 23 references.
Those who give up essential liberties for temporary safety deserve neither liberty nor safety