Corrosion of Cu-xZn alloys in slightly alkaline chloride solutions studied by stripping voltammetry and microanalysis

The mechanism of corrosion of Cu-xZn alloys (x = 10-40 wt %) in slightly alkaline chloride solutions was investigated by analysing solid reaction products by energy dispersive X-ray analysis (EDS) and dissolved reaction products by differential anodic pulse stripping (DAPS) voltammetry. The corrosion process was studied under open circuit and under potentiostatic conditions at selected potentials. Pure metals were studied comparatively so that an interacting effect of particular metal components in the alloy could be determined. All four Cu-xZn alloys show an improved behaviour compared to pure metals. Under open-circuit condition both components dissolve simultaneously in the solution. With increasing immersion time the preferential, dissolution of zinc in the solution becomes pronounced. It is the highest for Cu-10Zn and the lowest for Cu-30Zn alloy. Under potentiostatic control the dissolution mechanism depends on the electrode potential and changes from exclusive dissolution of zinc to simultaneous dissolution of both components with preferential dissolution of zinc. The latter decreases, as the electrode potential becomes more positive.     

Rapid determination of protein in plant material by flow injection spectrophotometry with trinitrobenzenesulfonic acid

The rapid determination of protein in plant material based on spectrophotometric determination of amino acids in protein hydrolysates with trinitrobenzenesulfonic acid has been adapted to flow injection analysis. With the manifold described, a routine sampling rate of 120 samples/h is possible, though this, as well as sensitivity, can easily be varied. The method was calibrated against the Kjeldahl method and a good correlation was obtained between the two methods over a wide range of protein values for beans.     

Tast polarography of europium(III)-l-histidine complex

Study of europium(III)-l-histidine complex has been made in sodium perchlorate at μ=0.1 by tast polarography. The reduction process appears to be quasi irreversible. The apparent rate constants have been determined byGellings method¹. With the knowledge ofE ₁ ^2/r and use ofLingane's method, one complex Eu(Histd)²⁺ with the instability constant 6.77×10^?5 is reported.     

Kinetik der Diazotierung der Chloraniline in methanolischer Chlorwasserstofflösung

The kinetics of the diazotization of o-, m-, p-chloroaniline in 0.005n- to 0.4n-methanolic HCl-solution at 25, 15, 0, ?10 ?20, and ?30°C was invertigated. It was found that the nitrosation reaction (the same as in¹) $$C_6 H_4 ClNH_2 + NOCl \mathop \rightleftharpoons \limits^k C_6 H_4 ClNH_2 NO^ + + Cl^ - $$ is a proceeding advance-back-reaction. The decomposition of C₆H₄ClNH₂NO⁺ by splitting off a proton is the rate determining step. The free activation enthalpies ΔG ^* for the nitrosation reaction, the activation entropies ΔS ^*, the activation enthalpies ΔH ^* and the activation energiesE _a at the given temperatures are calculated. The experimentally found and the calculated velocities are given in Tables 1–6. The equilibrium constants of the o-, m-, p-chloroanilinium ions, and nitrosyl-chloride in methanol are indicated in Table 7, diagram 1. TheK _M values (the ionic products of methanol, extrapolated at infinite dilution) together with theK _A values of Table 7 give theK _B values (p. 2) using the table¹⁰. The ΔG _B values can be calculated using equation ΔG _B = ?RTlnK _B Fig 2 shows the linear dependance of the logarithmus of the ΔG ^* values from the logarithmus of theK _B values.     

Polarisabilites moléculaires et effet diélectrique de milieu à l'état liquide. Étude théorique de la molécule d'eau et de ses diméres

The model of Onsager in which a polar molecule undergoes a reaction field due to the polarization of the molecular surroundings is used to evaluate by a S.C.F. calculation (CNDO/2 approximation) the modifications of a molecular structure in the liquid state.Application to water molecule and to three polar dimers for values of the dielectric constant varying between 3 and 78, shows that most of geometric parameters and dipoles moments vary of few per cent when the molecule is inserted in a liquid. In the liquid state dipole moments do not depend very much on the dielectric constant but energies and relative stabilities of isomers are strongly dependent on the medium.[/p]

     

Bestimmung von Aminosäuresequenzen in α-Keratose

Zusammenfassung Aus einem durch Trypsinabbau von -Keratose erhaltenen Gemisch von Peptiden wurden 15 neutrale, 5 saure und 2 basische Peptide durch Kombination papierchromatographischer und papierelektrophoretischer Methoden getrennt und in sehr geringen Mengen isoliert. Es wurden neben der Aminosäurezusammensetzung 14N-terminale Aminosäuren sowie einige Teilsequenzen in den untersuchten Peptiden ermittelt.Die mittlere Kettenlänge der Peptide beträgt 5,8 Aminosäuren.Mit 1 Tabelle3. Mitt. über Untersuchungen an -Keratose. 2. Mitt.:M. Fell undE. Schnabel, Hoppe-Seyler's Z. physiol. Chem.333, 218 (1963).     

A set of four soil reference materials with certified values of total element contents and their extractable fractions

A set of certified reference materials of four natural soils denoted as CRM 7001-4 was prepared. They consist of light sandy soils with normal and elevated, silty clay loam with normal, and loam with elevated element levels. Certified and/or information values were established for the total contents of the elements As, Ba, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, Zn, and their fractions, extractable with aqua regia, and boiling and cold 2 mol L^–1 nitric acid, from results of a 28 laboratory intercomparison using various methods of atomic absorption spectrometry, optical emission spectrometry, mass spectrometry, electrochemical methods, spectrophotometry, instrumental neutron activation analysis, and X-ray fluorescence.     

Reaktion von 5-Oxo-A-nor-3,5-secocholestan-3-säure mit einfachen Hydrazinderivaten

The reaction of 5-oxo-A-nor-3,5-secocholestan-3-oic acid (1) with simple N-mono and N,N-disubstituted hydrazines including acetylhydrazide was studied. Derivatives of 4-amino-4-aza-cholest-5-ene-3-one (2) were obtained.

---

---

Herrn Prof. Dr.H. Bretschneider mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Beiträge zur Grenzflächenchemie phosphororganischer Verbindungen

Zusammenfassung Die tertiären n-aliphatischen Phosphine spreiten auf Wasser spontan zu einem monomolekularen Film aus. Die Kompressionsisothermen der untersuchten tertiären aliphatischen Phosphine in homologer Reihe mit der Kettenlänge von C₄ bis C₁₆ wurden ausgemessen und die dabei auftretenden Filmzustände identifiziert. Das tertiäre C₅-Phosphin bildet realgasanaloge, die C₆–C₁₂-Phosphine flüssiganaloge und die längerkettigen Phosphine festanaloge Filme.Ein Übergang vom tertiären Phosphin zum Phosphinoxid hat auf die Filmbildung keinen Einfluß, es ergibt sich nur eine geringfügige Vergrößerung der molekularen Fläche von etwa 10%.Der auf den Filmdruck 0 extrapolierte molekulare Flächenbedarf wurde sowohl nach den herkömmlichen Verfahren aus denF/A-Diagrammen als auch mit einer anderen Methode aus denF·A/F-Isothermen berechnet: beide Werte zeigen sehr gute Übereinstimmung. Dabei zeigt der Vergleich mit dem aus den molekularen Abmessungen errechneten Flächenbedarf, daß die Phosphinmoleküle im komprimierten Film nicht vollständig in Pyramiden- bzw. Kegelform geordnet sind sondern daß die aliphatischen Ketten vom sechsten C-Atom an senkrecht auf der Substratoberfläche stehen. Der P-C-Winkel ist nicht für, die ganze Kette richtungsweisend, die flexiblen Kohlenwasserstoff ketten sind abgewinkelt. Mit zunehmender Kettenlänge wächst das Molekül nur noch senkecht in die Höhe, deshalb bleibt die molekulare Fläche ab C₆ annähernd konstant.

---

Summary Tertiäry n-aliphatic phosphines form on water surfaces spontanously monolayers. The force-area isotherms of a homologous series of phosphins with a chainlength varying from C₄ to C₁₆ were measured and the appearing states of the films were identified. The tertiary C₅ phosphine forms real-gas analogous films, the C₆ to C₁₂ phosphines liquid, analogous films and phosphines with lange carbon chains solid analogous films.A transition from tertiäry phosphines to the corresponding phosphine oxide has no influence on the formation of the films, it results only in an insignificant (10 p. c.) increase of the molecular area.The molecular area from the extrapolation to the film pressure of 0 was calculated by the customery methods out of theF/A diagramms, and by an other methods out of theFA/F isotherms. Good accordance of both values is shown. The area calculated from the molecular dimensions shows in comparison, that the phosphine molecules in comprimated films are not exactly disposed in pyramidal or conic shape, but that each aliphatic chain changes its direction after the sixth C-atom and stands vertically to the liquid-air interface. The direction of the chains is not determined by the angle of the P–C bonding, because the flexible carbon changes are distorted. With increasing chainlength, beginning from the tertiäry C₆ phosphin the carbon chains stand only vertically to the substrate. Therefore the need of molecular area remains almost constant.

---

---

Mit 8 Abbildungen und 5 Tabellen     

Reversible energy transfer

Analysis of the transient and steady-state kinetics of reversible energy transfer shows that while the interpretation of lifetime measurements is difficult unless the donor and acceptor lifetimes are appreciably different, quantum yield measurements are relatively easy to interpret.

---

Zusammenfassung Die Analyse der Kinetik der Übergangszustände und der stationären Zustände der reversiblen Energieübertragung zeigt, daß im Gegensatz zu einer schwierigen Interpretation der Messungen der Lebensdauer — es sei denn die Lebensdauer von Donor und Acceptor sind wesentlich voneinander verschieden — die Messungen der Quantumausbeute verhältnismäßig einfach zu interpretieren sind.

---

Résumé L'analyse de la cinétique de l'état transitoire et de l'état stationnaire du transfert réversible d'énergie montre que, si l'interprétation des mesures de durée de vie est difficile, à moins queles durées de vie du donneur et de l'accepteur soient très différentes, il est par contre relativement facile d'interpréter les mesures de rendement quantique.

---

---

Dedicated to the memory of Professor K. H. Hansen.