(e, 3e) test on e-e correlations in helium

The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class.     

Optical absorption of cobalt (II) in binary thallium borate glasses

The optical absorption spectra of cobalt (II) in Tl₂OB₂O₃ glasses have been studied and compared with those in binary alkali borate glasses. In thallium borate glasses cobalt (II) may be present in octahedral and/or in tetrahedral symmetry depending upon the composition of the glass. In low thallium borate glasses cobalt (II) is octahedral while the concentration of tetrahedral cobalt (II) increases with increasing Tl₂O content of the glass; the formation of tetrahedral cobalt (II) becomes noticeable when the concentration of Tl₂O reaches above the critical concentration of about 19 mol %. The ligand field parameters: 10Dq and B have been calculated from the absorption spectra of cobalt (II) in different glasses and it has been found that the Racah parameter, B, is more in Tl₂OB₂O₃ glasses than those in Na₂OB₂O₃ or K₂OB₂O₃ glasses of corresponding molar composition. This indicates that the donor capacity of the BO₄ group in thallium borate glasses is lower than that in alkali borate glasses; this is consistent with the NMR results in Tl₂OB₂O₃ glasses containing less than 20 mol % Tl₂O where three BO₄ groups have been found to form with each Tl₂O unit added.     

Micro and semi-micro determination of organic nitrogen by use of potassium bromate

After Kjeldahl digestion of an organic compound, nitrogen is determined by oxidation of the resultant ammonium sulphate with hypobromite produced in situ by the addition of an excess of potassium bromate and bromide in a special flask. The unreacted potassium bromate is determined iodometrically.     

Determination of traces of hydrogen in fluoro-organic compounds

The determination of traces of hydrogen in highly fluorinated compounds has been studied. Nitrogen and sulphur in the sample interfere slightly in the pyrolytic method of Miller etal. A straightforward combustion method is proposed in which the sample is burned in oxygen over magnesium oxide at 900° and the water formed is determined either gravimetrically or titrimetrically.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

The elimination of the distillation procedure in the Kjeldahl method

Summary The distillation process in the Kjeldahl method can be eliminated by applying the hypochlorite titration ofKolthoff andStenger. Mercury is used as catalyst; other catalysts which were tried interfered in the titration. Digestion and titration can be done in the same vessel on the micro scale, but a suitable vessel remains to be designed for this to be achieved on the semi-micro scale.The method is not applicable when pre-reduction is necessary, for all the reagents tested interfered with the subsequent titration.

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Zusammenfassung Durch Anwendung der Hypochlorittitration nachKolthoff undStenger läßt sich die Destillation bei der Stickstoffbestimmung nachKjeldahl umgehen. Quecksilber dient als Katalysator; andere Katalysatoren stören die Titration. Veraschung und Titration können im selben Gefäß im Mikromaßstab durchgeführt werden, aber bei der Analyse im Semimikromaßstab wird die zu titrierende Lösung besser in ein anderes Gefäß gebracht.Wenn eine vorhergehende Reduktion nötig ist, eignet sich die Methode nicht, da die hierzu nötigen Reagenzien die Titration stören.

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Résumé Il est possible d'éliminer la distillation que comporte la méthode deKjeldahl par application du titrage par l'hypochlorite deKolthoff etStenger. On emploie le mercure comme catalyseur; les autres catalyseurs qui ont été essayés gênent le titrage. Digestion et titrage peuvent être effectués dans le même récipient à l'échelle microanalytique mais il conviendrait de prévoir un récipient spécial pour permettre de réaliser cette condition à l'échelle semi-microanalytique.Cette méthode n'est pas applicable lorsqu'il est nécessaire d'effectuer une réduction préalable car les réactifs qui sont alors employés réagissent ultérieurement lors du titrage.

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We have great pleasure in dedicating this paper to our good friend Professor Dr.R. Strebinger on the occasion of his 70th birthday.

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Our thanks are due to Mr.E. Parry for carrying out check determinations.     

Fast iterative methods for symmetric sinc-Galerkin systems

The symmetric sinc-Galerkin method developed by Lund, when appliedto the second-order self-adjoint boundary value problem, givesrise to a symmetric coefficient matrix has a special structureso that it can be advantageously used in solving the discretesystem. In this paper, we employ the preconditioned conjugategradient method with banded matrices as preconditioners. Weprove that the condition number of the preconditioned matrixis uniformly bounded by a constant independent of the size ofthe matrix. In particular, we show that the solution of an n-by-ndiscrete symmetric sinc-Galerkin system can be obtained in O(nlog n) operations. We also extend our method to the self-adjointelliptic partial differential equation. Numerical results aregiven to illustrate the effectiveness of our fast iterativesolvers.     

Artifacts of the decalin-molecular sieve system in the analysis of mineral waxes

Analysis of commercial paraffin waxes by use of molecular sieves and decalin has been shown to give misleading results because of the formation of additional compounds. The source and the nature of these compounds have been investigated and it has been found that they are polymers of partially dehydrogenated decalin. Care should be taken when using this solvent in such analyses.     

(e, 3e) Differential cross section of He (21 S) and He (23 S)

The angular distribution of the five-fold differential cross section for the electron impact double ionization of He (2¹ S) and He (2³ S) has been studied. The kinematical conditions for maxima/minima in the angular distribution for the two cases have been compared. The two-step process for the double ionization is found to contribute very little in the triplet case.     

Aspects of the Chemistry of Poly (Ethylene Terephthalate). IV. Hydrolysis of Poly(Ethylene Terephthalate) in the Melt Phase

The effect of water vapor pressure on the molecular weight of molten poly (ethylene terephthalate) has been followed by measurement of the changes which occur in the intrinsic viscosity and the end-group concentrations upon hydrolysis. It was found that phosphoric acid is highly effective as a stabilizer; the hydrolysis rate constant (K_h) decreasing from 7.6 × 10^?7 mol^?1s^?1 for nonstabilized to 2.5 × 10^?7 mol^?1s^?1 for the stabilized polyester at 290°C and water vapor pressure of 20 mmHg.