Resolution concept for separation of curium from californium by ion-exchange chromatography

Different factors affecting separation of the tervalent actinides curium and californium by ion-exchange chromatography are discussed in the light of the resolution factor. The fact that resolution is inversely proportional to resin particle diameter and directly proportional to column length has been confirmed experimentally. The effects influencing resolution due to changes in flow-rate of the mobile phase used are dependent on resin particle diameter. Changes in temperature affect a number of variables influencing resolution.     

Polarographic behaviour of metal chelates of o,o'-dihydroxyazo dyes

The nature of complexes between various o,o'-dihydroxyazo dyes and metal ions, and their applications in polarographic chemical analysis, are described and discussed.     

The formation of vibrationally excited HD from atomic recombination on cold graphite surfaces

HD molecules formed in v"=3 and v"=4 have been detected by laser spectroscopy when a cold (15 K) graphite surface is irradiated with H and D atoms. Population of the v"=3, J"=0-6 and v"=4, J"=0-6 levels has been detected and the average rotational temperatures of the nascent HD were determined. These results are compared with previous data collected for the formation of HD in v"=1 and 2 under similar conditions. This comparison indicates that the nascent HD flux increases with increasing vibrational quantum number for v"=1-4.     

On the nature of pulsars

The paper contains a relatively non-technical summary of some recent work by the author and Jeremy Butterfield. The goal is to find a way of assigning meaningful truth values to propositions in quantum theory: something that is not possible in the normal, instrumentalist interpretation. The key mathematical tool is presheaf theory where multi-valued, contextual truth values arise naturally. We show how this can be applied to quantum theory, with the ‘contexts’ chosen to be Boolean subalgebras of the set of all projection operators.     

THE DECONVULATION OF ABSORPTION SPECTRA OF GREEN PLANT MATERIALS—IMPROVED CORRECTIONS FOR THE SIEVE EFFECT

The extinction (absorbance, optical density) of a suspension of algal cells or chloroplasts, etc. can be an a linear function of the absorption coefficient of the cell contents, even when the effects of scattering are negligible. The deviation from linearity is Duysens' sieve effect. The heights of absorption maxima of suspensions are depressed as compared with those of the “particle” contents. Duysens proposed an expression for correcting for this distortion; that expression proves to be a special approximate case of a more general one. This paper proposes an improved method of correction which utilizes this general expression, conventional expressions for particle absorption based on the Lorentz-Mie and Aden and Kerker equations for scattering and absorbing, and iterative methods for numerically deducing particle absorption coefficients from suspension parameters. The procedure is illustrated by applying it to previous experimental spectra of Chlorellu cells and spinach chloroplasts.     

The potentiometric titration of iron(II)/HCl solutions with permanganate

Summary Reagents other than the Zimmerman-Reinhardt reagent have been used to minimize the errors incurred when Fe(II)/HCl systems are titrated with MnO₄ ^–. Potentiometric studies made of the effect of these additives on the initial and equivalence point potentials show that salts whose anions stabilize the Mn(III) state affect the equivalence point potential more than those containing Mn(II). The cation also affects the result, e.g., H₂SO₄ ^– and Na₂SO₄-containing solutions show a greater equivalence potential change than do those containing (NH₄)₂SO₄ and K₂SO₄. Ce₂(SO₄)₃, reportedly an effective inhibitor, does not affect the equivalence point potential. Less titrant is required for 6 M HCl-containing Fe(II) solutions than for 1 M HCl-containing solutions-a result opposite to that expected and only partially explained by a more rapid air-oxidation of Fe(II) in 6 M HCl. The Pt electrode is not inert in this system.

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Zusammenfassung Bei einer Untersuchung der potentiometrischen Titration salzsaurer Eisen(II)-lösungen mit Permanganat wurde die Wirkung der verschiedenen für diese Bestimmung zur Verhinderung von Störungen empfohlenen ZusÄtze geprüft. Dabei ergab sich, da\ Salze, deren Anionen das dreiwertige Mangan stabilisieren, das Potential im Äquivalenzpunkt stÄrker beinflussen als solche, die zweiwertiges Mangan enthalten. Da\ auch das Kation das Ergebnis beeinflu\t ergab sich daraus, da\ bei H₂SO₄ und Na₂SO₄ eine grö\ere PotentialÄnderung im Äquivalenzpunkt beobachtet wurde als bei (NH₄)₂SO₄ und K₂SO₄. Bei Ce₂(SO₄)₃ wurde keine Wirkung auf die PotentialÄnderung festgestellt. Für 6 M salzsaure Fe(II)-Lösungen wurde weniger Titrationsmittel verbraucht als für 1 M salzsaure, was nur zum Teil mit der schnelleren Luftoxydation des zweiwertigen Eisens im 6 M HCl-Lösung erklÄrt werden kann. Die Platinelektrode erwies sich in diesem System nicht als inert.

     

The determination of tervalent chromium and iron in chromic acid

Chromic acid is analysed for tervalent chromium by separation of Cr(III) from Cr(VI) by precipitation as the hydrous oxide, with Zn(OH)(2) as a carrier. The hydrous oxide is collected by centrifugation and dissolved in perchloric acid, then Cr(III) is complexed with 1,2-diaminocyclohexanetetra-acetic acid and measured spectrophotometrically at 540 mmicro. Repetitive analysis of a sample of chromic acid showed 93 ppm of Cr(III) (s = 13, n = 9). Iron in chromic acid is also separated as the hydrous oxide, then dissolved in HCl, reduced to Fe(II) with hydroxylamine hydrochloride, complexed with bathophenanthroline disulphonic acid and measured spectrophotometrically at 533 mmicro. Repetitive analyses of a sample of chromic acid showed 2-6 ppm of iron (s = 0.35, n = 8).     

A transmission imaging spectrograph and microfabricated channel system for DNA analysis

In this paper we present the development of a DNA analysis system using a microfabricated channel device and a novel transmission imaging spectrograph which can be efficiently incorporated into a high throughput genomics facility for both sizing and sequencing of DNA fragments. The device contains 48 channels etched on a glass substrate. The channels are sealed with a flat glass plate which also provides a series of apertures for sample loading and contact with buffer reservoirs. Samples can be easily loaded in volumes up to 640 nL without band broadening because of an efficient electrokinetic stacking at the electrophoresis channel entrance. The system uses a dual laser excitation source and a highly sensitive charge-coupled device (CCD) detector allowing for simultaneous detection of many fluorescent dyes. The sieving matrices for the separation of single-stranded DNA fragments are polymerized in situ in denaturing buffer systems. Examples of separation of single-stranded DNA fragments up to 500 bases in length are shown, including accurate sizing of GeneCalling fragments, and sequencing samples prepared with a reduced amount of dye terminators. An increase in sample throughput has been achieved by color multiplexing.