Abhängigkeit der UV-Absorption binärer Styrol-Copolymerisate von der Länge der Styrolsequenzen

The UV-spectrometer is proposed in the literature as a second detector for gel permeation chromatography, independent of the usual differential refractometer. The intention is to get information on the variation of the chemical composition of styrene copolymers with molecular weight. The present paper disproves the usual assumption that UV-absorption of styrene copolymers is depending only on the concentration of phenyl rings. However, the absorption also depends on the length of the styrene sequences and therefore mostly on the monomer ratio in the copolymer. The UV-spectra of binary styrene copolymers with ecrylonitrile, maleic anhydride and butadiene were measured at different monomer ratios. From the measurements we calculated the molar absorption coefficient of the phenyl ring for different absorption bands. In comparison with homopolystyrene it is shown that both the position and the absorption coefficient of the bands can depend on the sequence length distribution of the copolymers. We suggest this to be caused by dispersion interactions between neighbouring phenyl rings. Consequences for the use of a UV-spectrometer as a detector for gel permeation chromatography are discussed.     

Die Beeinflussung der Reaktion bei der Oxäthylierung von Fettsäuremonoäthanolamiden

Influencing the Oxyethylation Reaction of Fatty Acid Mono-Ethanolamides In the reaction of fatty acids or methyl esters of fatty acids with mono-ethanolamine, fatty acid-aminoethyl esters and di-fatty acid-ethanolamide esters are formed in addition to mono-ethanolamides of fatty acids. The equilibrium is predominantly towards the mono-ethanolamide of fatty acid. This equilibrium reaction interferes considerably during the oxyethylation of ethanolamides of fatty acids, since at the temperature of oxyethylation the aforestated compounds and their oxyethylation products are formed. Furthermore, amino-oxyethylate and heterocyclic products are always formed which lead to dark and odorous reaction products. Investigations were carried out in order to determine the influence of reaction temperature, catalyst concentration, and nature of starting material on the composition of oxyethylates that are formed by oxyethylation of fatty acid ethanolamides.     

Einfluß der Bleicherde auf die Fettsäurebildung während der Bleichung

Effect of Bleaching Earth on the Formation of Fatty Acids during Bleaching Investigations were carried out with neutralized soybean and cottonseed oils in order to determine the effect of acid content of bleaching earths with different activities on the formation of free fatty acids during the adsorptive bleaching. The free fatty acid content of the oils under investigation decreased with increasing acidity of the highly active and moderately active bleaching earth. The increase in acid value of the oil during bleaching is essentially dependent on the duration of bleaching and amount of bleaching earth employed. The water content of the oil has no decisive effect.     

Änderung der Oxidationsstufe des Kobaltund Vanadium-Beschleunigers während der Härtung ungesättigter Polyesterharze

During the free radical copolymerization of unsaturated polyesters with styrene the metal in the accelerator is oxidized and reduced alternatively. In the case of cobalt and vanadium accelerators this causes a change in the colour of the resin. This change in the colour makes it feasible to determine colorimetrically the content of the higher and the lower valency of the metal during the polymerization.     

Untersuchungen über die Zusammenhänge zwischen thermodynamischer Stabilität der Kakaobutter und der Lagerbeständigkeit der Schokolade

Investigations on the Relationship between the Thermodynamic Stability of Cocoabutter and Storage Stability of Chocolate In a previous work

1 H. Witzel u. K. Becker, Über die Kristallstruktur der Kakaobutter, Fette · Seifen · Anstrichmittel 71 , 507 [1969].

, the crystalline structures and molecular arrangements of unstable pre-β-form and stable β-form of cocoabutter could be elucidated. In the present work, attempts were made to determine quantitatively the amounts of pre-β-form and β-form of cocoabutter in chocolate by x-ray technique. Furthermore, the influence of the amount of unstable pre-β-form on the rate of formation of fat bloom was investigated. It was found that the quantitative determination of pre-β- and β-forms is not possible. However, from the intensity of some x-ray reflexes conclusions regarding the resistance of chocolate towards the formation of fat bloom can be drawn.     

Über die Abhängigkeit der Dichte,der Oberflächenspannung und der Viskosität von der Kettenlänge bei Äther-Estern des Äthylenglykols im Vergleich zu anderen homologen Reihen

The Relationship of Density, Surface Tension and Viscosity to the Chain-Length of Ether-Esters of Ethyleneglycol in Comparison to Other Homologous Series A number of glycolether-esters of the type R₁? O? CH₂CH₂? OCOR₂ were synthesized. For these compounds as well as for a few other non-branched homologous series, the following relationship showing the dependence of density, surface tension and viscosity from the chain-length was observed: X_t = X_{t, Z = ∞} + k_t/Z, whereby X_t represents the physical property concerned at the temperature t, X_{t, Z = ∞} the limiting value of the aforesaid property at infinite chain-length and k_t a characteristic constant of the homologous series involved at the temperature t. The above relationship was found to be generally applicable with sufficient accuracy.     

Veränderungen der Fettsäurezusammensetzung von Lipidfraktionen aus Kartoffeln während der Lagerung

Alterations in Fatty Acid Composition of Lipid Fractions from Potatoes During Storage Fatty acid composition of total lipids of the lecithin and cephalin fractions were determind by gas chromatography in samples of fresh potatoes and those stored for 8 months in cold. Moreover, a method for isolation of the pure cephalin fraction is reported. In all the three fractions the percentage of linolenic acid increased during storage, whereas the content of linoleic acid decreased. Other fatty acids remained practically unchanged during the storage. An additional experiment in which powdered freeze-dried potatoes were stored under undesirable conditions showed, as expected, that the content of unsaturated fatty acids decreased strongly. The results are discussed.     

Oberflächenaktive Derivate der Rizinolsäure

Surface Active Derivatives of Ricinoleic Acid Studying the dependence of tenside properties on their constitution, often all the attention is paid to the hydrophilic end, whereas the hydrophobic end is of minor importance. Studies of tensides for many years, produced of special fatty acids, have shown that these have a significant influence on many tenside properties. That does not only regard the special tenside properties as e.g. foaming, washing, purifying and emulsifying but especially the dermatological and lexicological compatibility of these compounds. Ricinoleic acid or its soaps and triglycerides have been known for long as substances which are very well tolerated by skin. Partly they contain marked skin protection or skin preserving properties. It is therefore of significant interest in which way these properties can be transferred to synthetic tensides. This was investigated as well with anionic and non ionogenic derivatives of the ricinoleic acid as with amphoter and kationic derivatives and led partly to surprising results.     

Zur Essentialität der Polyenfettsäuren

On the Essential Nature of Polyunsaturated Fatty Acids Several plant oils contain polyunsaturated fatty acids which cannot be synthesized by the human body. They have been recognized as essential nutrients, as characteristic symptoms are caused by deficient intake. The LCP-fatty acids are incorporated into structural lipids and cell membrans and influence directly their properties. LCP-fatty acids are precursors of prostaglandins, lencotrienes and eicosanoid mediators, which intern regulate numerous cell functions. The effects of LCP-fatty acids on pre- and postnatal growth and the nervous system are discussed in detail.     

Der einfluß der luftfeuchte bei der verfärbung von PVC während der bewitterung und bei der anschließenden dunkellagerung

The influence of humidity on the light-fastness and the dark time yellowing of white PVC and special changes of the irradiated surfaces are described. The results show, that the boundary surface climate at the irradiated specimen surfaces has a decisive influence on the ageing results.     

Beiträge der Prozeßleittechnik zur Qualitätssicherung in der chemischen Produktion

Contributions of Process Control to Quality Assurance in the Chemical Industry. Through their functions of measurement, i.e. the acquisition of quantities relating to the process and the product, and adjustment, i.e. the modification of control values, process control engineering and process automation represent the basis of all operative control of quality. The functions of control, regulation, and operator support are likewise instruments ensuring the maintenance of quality-relevant process and product specifications. Utilisation of the considerable potential of these tried and tested control methods is logical in the case of chemical processes and should receive more attention in quality management.     

Schätzung der Investitionskosten bei der Prozeßentwicklung

Estimation of Investment Costs in Process Development. This article gives an overview of plant cost estimating; the corresponding data and authors who have described the individual methods can be obtained from the primary literature. The definitions, the present authors, own data and experience gained in Germany, the pros and cons in practice of each cost estimating method are presented. The turnover ratios, capacity ratio exponents, step-counting methods, and factor methods are emphasized for cost estimating in a situation of comparative uncertainty in the early stages of a project, because unit cost methods and detailed cost estimating are often used for budgeting.     

Zur Berechnung der Temperaturabhängigkeit der kritischen Mizellbildungskonzentration endständiger Alkansulfonate

Concerning the Calculation of the Temperature Dependence of Critical Mizellization Concentration Values for Terminal Alkane Sulphonates Tschernikov's equation for calculating c_M-values of homologous sodium alkane-1-sulphonates at different temperatures has been modified. By means of this modified equation A values of Stauff/Klevens' equation have been calculated. These A values show a linear dependence on temperature. In a modified form presented in this paper Stauff/Klevens' equation can now be used for calculating c_M-values of homologous sodium alkane-1-sulphonates at different temperatures.     

Die Bestimmung der Erucasäure in Gegenwart von der Docosensäure

Determination of Erucic Acid in the Presence of Isomeric Docosenoic Acids In the countries belonging to the European Community the Erucic Acid Directive of 20. 7. 1976 restricts the level of erucic acid (not docosenoic acid) in edible oils and fats and foodstuffs to which fats and oils have been added to 5%. For the determination of the erucic acid content the EEC-Directive no. 80/891 specifies a procedure that enables the determination of erucic acid even in the presence of isomeric docosenoic acids. According to this procedure the methyl esters of fatty acids are first fractionated at –25°C on thin-layer plates containing silver nitrate. Thus, erucic acid (13-cis-docosenoic acid) is separated from isomeric docosenoic acids, such as cetoleic acid (11-cis-docosenoic acid) and trans-docosenoic acids, that are frequently found in crude and hydrogenated fish oils. The erucic acid content can be determined by gas chromatography of the eluted fractions after the addition of an internal standard. The method has been developed in collaboration with the Federal Center for Lipid Research. Their work concerned with the development of the method is reported. It includes the separation of pure docosenoic acid isomers and the determination of erucic acid content in a series of crude and hydrogenated fish oils.