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Author: K. Paech Publisher: Springer Science & Business Media ISBN: 3642649580 Category : Science Languages : de Pages : 774
Book Description
If, following the solvent extraction of a hydrocarbon from a plant, it is not known whether it is one or the other, a method of distinguishing the two is described by HENDRICKS, WILDMAN and JONES (1946). The technique involves the infra-red absorption spectra of the two isomers. At about 12 mp. the relative absorption coefficient of rubber is 42% greater than for gutta. ScHLESINGER and LEPER (1951) describe two procedures for separation of the rubber and gutta hydrocarbons from large quantities of crude chicle. In one, the chicle is extracted with benzene which dissolves both isomers. An excess absolute ethyl acetate is added and the mixture stored at 5° C overnight. The gutta precipitates out and the rubber remains in solution. The other method is as follows: (1) Ten grams of chicle are extracted with acetone for 24 hours in a Soxhlet extraction apparatus. (2) The insoluble material in the thimble is allowed to .. it dry, then immersed in 150 ml. of cold Skellysolve B in a refrigerator at 10° C and· allowed to stand for 48 hours with occasional agitation. (3) The thimble is then removed from the solvent and the enclosed residue washed several times with fresh, cold Skellysolve B. (4) An excess of acetone and a few drops of a concentrated aqueous solution of sodium iodide are added to the combined Skellysolve B extract and washings and allowed to stand overnight in a refrigerator.
Author: K. Paech Publisher: Springer Science & Business Media ISBN: 3642649580 Category : Science Languages : de Pages : 774
Book Description
If, following the solvent extraction of a hydrocarbon from a plant, it is not known whether it is one or the other, a method of distinguishing the two is described by HENDRICKS, WILDMAN and JONES (1946). The technique involves the infra-red absorption spectra of the two isomers. At about 12 mp. the relative absorption coefficient of rubber is 42% greater than for gutta. ScHLESINGER and LEPER (1951) describe two procedures for separation of the rubber and gutta hydrocarbons from large quantities of crude chicle. In one, the chicle is extracted with benzene which dissolves both isomers. An excess absolute ethyl acetate is added and the mixture stored at 5° C overnight. The gutta precipitates out and the rubber remains in solution. The other method is as follows: (1) Ten grams of chicle are extracted with acetone for 24 hours in a Soxhlet extraction apparatus. (2) The insoluble material in the thimble is allowed to .. it dry, then immersed in 150 ml. of cold Skellysolve B in a refrigerator at 10° C and· allowed to stand for 48 hours with occasional agitation. (3) The thimble is then removed from the solvent and the enclosed residue washed several times with fresh, cold Skellysolve B. (4) An excess of acetone and a few drops of a concentrated aqueous solution of sodium iodide are added to the combined Skellysolve B extract and washings and allowed to stand overnight in a refrigerator.
Author: K. Biemann Publisher: Springer Science & Business Media ISBN: 3642459935 Category : Science Languages : en Pages : 563
Book Description
123 phase and hence have no direct bearing on the retention time of solutes. However in gas-solid chromatography, a considerable quantity of the mobile phase may be adsorbed on the surface of the stationary adsorbent which diminishes the column's effective length and ability to retain solutes. In this respect helium has been found to be preferable to most other gases (GREENE and Roy, 1957) because it is adsorbed to the least extent. 3. Packed columns offer a considerable resistance to flow, which may create a pressure differential between inlet and outlet of sufficient magnitude to cause an unfavorable flow rate through a significant length of the column. A reduced inlet/outlet pressure ratio can be obtained by using light molecular weight gases toward which the column packing shows the greatest permeability. The flow rate of the mobile phase is normally adjusted by altering the column inlet pressure, for which purpose commercial pressure regulators of sufficient accuracy are available. Quantitative measurements of the flow rate can be made by a number of methods, including rotameters, orifice meters, soapfilm flow meters and displacement of water. The former two methods are the most con venient but the least accurate; moreover they create a back pressure and are temperature dependent whereas although the moving soap bubble is cumbersome to employ and unusable for continuous readings, it is preferred when the highest accuracy is required.
Author: Karl Paech Publisher: Springer ISBN: 9783662232712 Category : Science Languages : de Pages : 542
Book Description
Viele bedeutende Errungenschaften der modernen Biologie sind erst nach Erfindung und Anwendung von leistungsfähigen Methoden möglich geworden. Man kann zwar nicht sagen, daß wir in einem "Zeitalter der Methoden" leben, aber jeder Schritt zur Lösung eines wichtigen biologischen Problems mußte und muß durch die Entwicklung einer geeigneten Methode vorbereitet werden. Es gibt nicht viele "klassische" Verfahren, die sich in der physiologisch-chemischen Forschung erhalten haben. Physik und Chemie entdecken immer wieder spezi fische, genauere und bequemere analytische Möglichkeiten, die von Biochemikern übernommen und für die Anwendung auf Pflanzenmaterial abgewandelt werden. Wenn solche neuen Methoden in rein analytischen Zeitschriften veröffentlicht werden, so sind sie zwischen analytischen Verfahren für alle möglichen Gebiete der Chemie, vom Petroleum bis zu Schwermetallegierungen, verborgen. Erschei· nen sie aber als methodischer Teil in den Arbeiten über spezielle biochemische Probleme, so gibt oft weder der Titel der Arbeit noch die Zusammenfassung einen Hinweis auf die wertvolle Methode und ihre Anwendungsmöglichkeiten. Neue leistungsfähige Methoden erreichen deshalb oft nicht unmittelbar alle die Forscher, die bei ihren Arbeiten größten Nutzen daraus ziehen könnten. Das waren die entscheidenden Überlegungen, die zur Planung dieses Handbuchs führten. Nach unseren Erfahrungen besteht ein Bedürfnis für eine moderne Sammlung zuverlässiger Methoden der Pflanzenanalyse vor allem auch in weiten Kreisen der angewandten Botanik, von landwirtschaftlichen und Gartenbau-Insti tuten bis zu pharmazeutischen und technischen Untersuchungsanstalten, die mit pflanzlichem Material zu tun haben.
Author: K. Paech
Author: K. Paech
Author: B.D. Sanwal
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Author: Karl Paech
Author: K. Paech
Author: K. Biemann
Author: 
Author: K. Paech
Author: Karl Paech
Author: Karl Paech