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.
Modern Methods of Plant Analysis / Moderne Methoden der Pflanzenanalyse
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.
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.
Moderne Methoden der Pflanzenanalyse
Author: Karl Paech
Publisher:
ISBN:
Category : Plants
Languages : en
Pages : 544
Book Description
Publisher:
ISBN:
Category : Plants
Languages : en
Pages : 544
Book Description
Moderne Methoden der Pflanzenanalyse / Modern Methods of Plant Analysis
Author: K. Paech
Publisher: Springer Science & Business Media
ISBN: 3642649580
Category : Science
Languages : en
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.
Publisher: Springer Science & Business Media
ISBN: 3642649580
Category : Science
Languages : en
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.
Modern Methods of Plant Analysis / Moderne Methoden der Pflanzenanalyse
Author: K. Paech
Publisher: Springer Science & Business Media
ISBN: 3642649556
Category : Science
Languages : en
Pages : 639
Book Description
Publisher: Springer Science & Business Media
ISBN: 3642649556
Category : Science
Languages : en
Pages : 639
Book Description
Modern Methods of Plant Analysis
Author: B.D. Sanwal
Publisher:
ISBN:
Category :
Languages : de
Pages : 512
Book Description
Publisher:
ISBN:
Category :
Languages : de
Pages : 512
Book Description
Bulletin
Author: Srpsko hemijsko društvo
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 558
Book Description
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 558
Book Description
Der Stoffwechsel Sekundärer Pflanzenstoffe / The Metabolism of Secondary Plant Products
Author:
Publisher: Springer Science & Business Media
ISBN: 3662267845
Category : Science
Languages : en
Pages : 869
Book Description
Publisher: Springer Science & Business Media
ISBN: 3662267845
Category : Science
Languages : en
Pages : 869
Book Description
Technical Bulletin
Author:
Publisher:
ISBN:
Category : Agriculture
Languages : en
Pages : 292
Book Description
Publisher:
ISBN:
Category : Agriculture
Languages : en
Pages : 292
Book Description
Advances in Structure Research by Diffraction Methods
Author: R. Brill
Publisher: Elsevier
ISBN: 1483152286
Category : Science
Languages : en
Pages : 257
Book Description
Advances in Structure Research by Diffraction Methods reviews advances in the use of diffraction methods in structure research. Topics covered include the dynamical theory of X-ray diffraction, with emphasis on Ewald waves in theory and experiment; dynamical theory of electron diffraction; small angle scattering; and molecular packing. This book is comprised of four chapters and begins with an overview of the dynamical theory of X-ray diffraction, especially in terms of how it explains all the absorption and propagation properties of X-rays at the Bragg setting in a perfect crystal. The next chapter describes the dynamical theory of electron diffraction, paying particular attention to unconventional structure analysis in connection with the problems of absorption. The most important features of the background of small angle analysis are then examined, and some examples showing the direct analysis of small angle scattering (sometimes in combination with wide angle scattering) are provided. The last chapter deals with crystals built from molecules and their peculiar geometrical features. The principle of close packing of molecules in an organic crystal is also described, along with lattice dynamics, hydrogen bonds in crystals, and the rotational crystalline state. This monograph will be a useful resource for practitioners and researchers in physics and crystallography.
Publisher: Elsevier
ISBN: 1483152286
Category : Science
Languages : en
Pages : 257
Book Description
Advances in Structure Research by Diffraction Methods reviews advances in the use of diffraction methods in structure research. Topics covered include the dynamical theory of X-ray diffraction, with emphasis on Ewald waves in theory and experiment; dynamical theory of electron diffraction; small angle scattering; and molecular packing. This book is comprised of four chapters and begins with an overview of the dynamical theory of X-ray diffraction, especially in terms of how it explains all the absorption and propagation properties of X-rays at the Bragg setting in a perfect crystal. The next chapter describes the dynamical theory of electron diffraction, paying particular attention to unconventional structure analysis in connection with the problems of absorption. The most important features of the background of small angle analysis are then examined, and some examples showing the direct analysis of small angle scattering (sometimes in combination with wide angle scattering) are provided. The last chapter deals with crystals built from molecules and their peculiar geometrical features. The principle of close packing of molecules in an organic crystal is also described, along with lattice dynamics, hydrogen bonds in crystals, and the rotational crystalline state. This monograph will be a useful resource for practitioners and researchers in physics and crystallography.
Foodborne Disease Handbook
Author: Y. H. Hui
Publisher: CRC Press
ISBN: 1351088998
Category : Technology & Engineering
Languages : en
Pages : 1219
Book Description
The Foodborne Disease handbook, Second Edition, Revised and Expanded, could not be appearing at a more auspicious time. Never before has the campaign for food safety been pursued so intensely on so many fronts in virtually every country around the world. This new edition reflects at least one of the many aspects of that intense and multifaceted campaign: namely, that research on food safety has been very productive in the years since the first edition appeared. The Handbook is now presented in four volumes instead of the three of the 1994 edition. Volume 3 of this series of books on food gums and hydrocolloids continues with a pragmatic coverage of three important categories of gum, i.e., the cellulose gums, the plant seed gums, and the pectins. The chemical, physical and functional properties of each of the important food gums in these categories are reviewed and discussed in relation with their utility in food product applications. The four volumes are composed of 86 chapters, a 22% increase over the 67 chapters of the first edition. Much of the information in the first edition has been carried forward to this new edition because that information is still as reliable and pertinent as it was in 1994. This integration of the older data with the latest research findings gives the reader a secure scientific foundation on which to base important decisions affecting the public‘s health.
Publisher: CRC Press
ISBN: 1351088998
Category : Technology & Engineering
Languages : en
Pages : 1219
Book Description
The Foodborne Disease handbook, Second Edition, Revised and Expanded, could not be appearing at a more auspicious time. Never before has the campaign for food safety been pursued so intensely on so many fronts in virtually every country around the world. This new edition reflects at least one of the many aspects of that intense and multifaceted campaign: namely, that research on food safety has been very productive in the years since the first edition appeared. The Handbook is now presented in four volumes instead of the three of the 1994 edition. Volume 3 of this series of books on food gums and hydrocolloids continues with a pragmatic coverage of three important categories of gum, i.e., the cellulose gums, the plant seed gums, and the pectins. The chemical, physical and functional properties of each of the important food gums in these categories are reviewed and discussed in relation with their utility in food product applications. The four volumes are composed of 86 chapters, a 22% increase over the 67 chapters of the first edition. Much of the information in the first edition has been carried forward to this new edition because that information is still as reliable and pertinent as it was in 1994. This integration of the older data with the latest research findings gives the reader a secure scientific foundation on which to base important decisions affecting the public‘s health.